6th Symposium on Phosphorus in

Soils and Plants

From Molecular Scale to Ecosystems

10 - 13 September 2018🞄Leuven (BE)

Published By

The organizing committee of the 6th Symposium on Phosphorus in Soils and Plants (PSPS)- Katholieke Universiteit Leuven (KUL)

Editorial Processing: Georgina Guzmán Rangel

Copyright © 2018 Katholieke Universiteit Leuven Editorial

All rights reserved. Nothing from this publication may be reproduced, stored in computerized systems or published in any form or manner, including electronic, mechanical, reprographic or fotographic, without prior written permission from the publisher KUL.

The individual contributions in this publication and any liabilities arising from them remain the responsibility of the authors

Distributed by PSP6/ Katholieke Universiteit Leuven (KUL) Division of Soil and Water Management Kasteelpark Arenberg 20, 3001 Leuven Belgium

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The Katholieke Universiteit Leuven welcomes the

6th symposium on Phosphorus in Soils and Plants (PSP6)

From Molecular Scale to Ecosystems Monday 10 to Thursday 13, September 2018 in Leuven, Belgium

Welcome to PSP6 in Leuven.

On behalf of the International Scientific Committee and Local Organizing Committee,

it is a pleasure for me to welcome you to this event in Leuven. This PSP6 is the sixth

international symposium of a successful series on Phosphorus Dynamics in the Soil-

Plant Continuum that was launched in Beijing (China) in 2000, then went to Perth

(Australia) in 2003, Uberlandia (Brazil) in 2006, Beijing (China) in 2010 and

Montpellier (France) in 2014.

Phosphorus is an intriguing element. The phosphate anion that is used by biota is

one of the least soluble nutrients in the environment, yet life has evolved in using it

at relative large concentrations for energy storage (ATP), information (DNA) and as

a highly ionic molecule in different biomolecules. Life has evolved in coping with its

poor solubility by developing efficient roots, associations with microorganisms and

by developing efficient uptake strategies. Phosphate is a finite resource and the

“peak P” price of rock phosphate has reminded us that the exploitation of this

element in agroecosystems needs to be carefully managed, including its recycling. In

this conference, about 250 delegates have submitted their work on phosphate in

soils and plants showing the different aspects of the fate and effect of phosphate in

soils and plants. We will be faced this week with work at extremely different scales,

starting from studies of molecular forms of phosphate esters to research showing

that soil P availability affects biodiversity in tropical rainforests. Fundamental

chemical questions about reaction times will be addressed but you will also listen

how P scarcity affects rural development. All presentations have phosphorus as a

common element, the one that is intriguing, that gives us information and energy!

The themes of PSP6 are:

Theme 1: Phosphorus forms, availability and cycling in soils

Theme 2: Phosphorus acquisition by plants and microorganisms

Theme 3: Phosphorus utilization and signaling in plants

Theme 4: Sustainable intensification of phosphorus supply in food production

Theme 5: Impact of phosphorus on environmental quality and on biodiversity

I would like to thank many people for making this event a success: FuSuo Zhang and

Zed Rengel for initiating this PSP series, the International Scientific Committee for

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spending extra time in selecting the abstracts, the key note speakers and for

discussing the program topics and the sponsors for their contributions. Above all, I

would like to thank the Local Committee who has worked hard in the last few months

in all organizational matters, thank you Charlotte, Kris, Kristien&team, Gina,

Maarten, Sophie, Pieterjan, Ruben, Erina, Toon, Laura, Karlien, Fien, Tobias, Roel,

Ivan, Stefaan and Olivier.

Welcome also at the Katholieke Universiteit

Leuven, founded in 1425 and one of the oldest

universities worldwide. Research on PSP probably

started after the original focus on arts, law and

medicine but we can state that we do have a long

tradition in that topic. We will also show you

around this week, not only in Leuven but also in

Tervuren to one of our Royal buildings.

And now, sit back, browse this book, listen to the program, reflect, interact and

network. I hope you enjoy it!

Erik Smolders

Chairman

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Sponsors

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Contents

Welcoming word 1

Sponsors 3

Organizers Scientific Committee 5

Local Committee 6

Practical information 7

JM-MW Auditorium Location Diagram 9

Program 10

Abstracts 19

Monday 10 September Keynote Presentations 21

Oral Presentations 25

Posters 49

Tuesday 11 September Keynote Presentations 119

Oral Presentations 123

Posters 143

Wednesday 12 September Keynote Presentations 211

Oral Presentations 215

Posters 231

Thursday 13 September Keynote Presentations 283

Oral Presentations 285

First author index 303

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Scientific Committee Erik Smolders –

Chairman KU Leuven (Belgium)

Martin Blackwell – Rothamsted Research (UK)

Else K. Bünemann – FiBL (Switzerland)

Timothy S. George – James Hutton Institute (UK)

Philip Haygarth – Lancaster University (UK)

Philippe Hinsinger – INRA (France)

Olivier Honnay – KU Leuven (Belgium)

Iver Jakobsen - Københavns Univerisitet (Denmark) Ivan Janssens –

UAntwerpen (Belgium) Hong Liao –

Fujian Agriculture and Forestry University (China) Jonathan Lynch –

Penn State University (USA) Mike McLaughlin –

University of Adelaide (Australia) Roel Merckx –

KU Leuven (Belgium) Stefaan De Neve – UGent (Belgium)

Laurent Nussaume – CEA Cadarache (France) Generose Nziguheba –

IITA (Kenya) Javier Paz-Ares –

CNB (Spain) Josep Peñuelas –

CSIC (Spain) Yves Poirier –

University of Lausanne (Switzerland) Matthias Wissuwa –

JIRCAS (Japan) Alan Richardson – CSIRO (Australia)

Jianbo Shen – China Agricultural University (China)

Federica Tamburini – ETH Zürich (Switzerland)

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Local Committee Erik Smolders –

Chairman KU Leuven (Belgium) Fien Amery –

ILVO (Belgium) Pieterjan De Bauw – KU Leuven (Belgium)

Kristien Van Crombrugge - KU Leuven (Belgium) Tobias Ceulemans – KU Leuven (Belgium)

Kris Dox – KU Leuven (Belgium) Maarten Everaert – KU Leuven (Belgium)

Olivier Honnay – KU Leuven (Belgium)

Ivan Janssens – UAntwerpen (Belgium)

Roel Merckx – KU Leuven (Belgium) Stefaan De Neve – UGent (Belgium)

Erina Shimamura – KU Leuven (Belgium)

Toon Van Dael – KU Leuven (Belgium)

Mieke Verbeeck – KU Leuven (Belgium)

Charlotte Vermeiren – KU Leuven (Belgium) Ruben Warrinnier – KU Leuven (Belgium)

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ABSTRACTS

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KEYNOTES Monday 10 September

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0 Foraging for better root traits: phosphorus acquisition efficiency in a critical

pasture species

Rebecca E. Haling1, Adeline Becquer2, Anne Warren1, Adam Stefanski1, Jonathan W.

McLachlan1,3, Daniel R. Kidd4, Megan H. Ryan4, Graeme A. Sandral5, Richard C. Hayes5, Richard

J. Flavel3, Chris N. Guppy3, Richard J. Simpson1

1CSIRO Agriculture and Food, GPO Box 1700, Canberra, 2601, Australia. 2 INRA, UMR Eco&Sols, 2 place Viala, 34060 Montpellier, Cedex 1, France. 3University of New

England, Armidale, NSW, 2351, Australia. 4School of Plant Biology, The University of Western

Australia, Perth, Australia. 5NSW Department of Primary Industries, Wagga Wagga, Australia.

Keywords: root morphology, legumes

Pastures grown on P-deficient soils in temperate southern Australia use mixtures of

grasses and legumes. The main legumes (Trifolium and Medicago spp.) are highly

productive across a wide range of environments but have high ‘critical’ P

requirements (i.e. the P supply needed for near-maximum yield) relative to the

grasses with which they grow. Improving the P-efficiency of the most important

legume (T. subterraneum), or developing the agronomic merit of alternatives that

are already P-efficient (e.g. Ornithopus spp.) would deliver reductions in P fertiliser

inputs, improve farm incomes, and achieve better use of scarce nutrient resources.

Here we describe research to improve the P efficiency of T. subterraneum. Field and

controlled-environment experiments, with various pasture legume species, have

demonstrated that substantial differences in the nutrient foraging potential of their

roots determines their requirement for P fertiliser. Three key root morphology traits

ensure efficient P acquisition from low P soil: development of high root length, high

specific root length and long root hairs. Ornithopus spp. deploy an “optimal”

combination of these root traits, efficiently maximising soil exploration to capture

more P and to yield well in low P soils. In contrast, Trifolium subterraneum develops

long roots in response to low P but has low specific root length and short root hairs

which limit its ability to explore soil for P. Within T. subterraneum, variation exists in

specific root length and root proliferation. These key factors determine intra-specific

variation in P acquisition with the best genotypes achieving twice the yield of the

worst in low P soil. The short root hairs on T. subterraneum (0.2-0.4 mm) are a major

factor limiting P acquisition efficiency. Wider studies of nutrient foraging root traits

among genetically-allied Trifolium species from the Section Trichocephalum

revealed substantial differences in propensity for root foraging (11-35 cm root/cm3

soil) and root hair length (0.2-0.5 mm) but, like T. subterraneum, no genotypes

tested to date have root foraging traits in the optimal combinations achieved by

Ornithopus spp. To drive further substantive change in the P efficiency in the key

pasture legume, T. subterraneum, it will be necessary to break through apparent

intra-specific ‘boundaries’ for specific root length and root hair length by identifying

radical ecotypic outliers, inter-specific introgression or directed mutagenesis.

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Symbiosis-induced rice phosphate transporter PT13 mediates cellular

phosphate efflux

Shu-Yi Yang1,2,3, Yansheng Wu4, Pieter de Waard5, Henk van As6, Yves Poirier2, Zhonglin Shang4,

Enrico Martinoia7 and Uta Paszkowski1

1 Department of Plant Sciences, University of Cambridge, Cambridge, CB2 3EA, UK. 2 Department of Plant Molecular Biology, University of Lausanne, 1015 Lausanne,

Switzerland. 3 Institute of Plant Biology, National Taiwan University, 10617 Taipei, Taiwan

4 College of Life Science, Hebei Normal University, Shijiazhuang 050024, Hebei Province, China. 5 Wageningen NMR Center, Wageningen University, 6708 HA Wageningen, The Netherlands

6 Department of Agrotechnology and Food Sciences, Wageningen University, 6708 HA

Wageningen, The Netherlands 7 Institute of Plant Biology, University of Zurich, 8008 Zurich, Switzerland.

Keyword: symbiosis, homeostasis, transport, rice

Most plants acquire phosphorus in the form of inorganic phosphate (Pi) via

association with mutualistic arbuscular mycorrhizal (AM) fungi. Fungal hyphae take

up Pi from the soil and deliver it to the plant inside inner cortex cells at highly

branched hyphal structures, the arbuscules. In rice, two PHosphate Transporter 1

(PHT1) type of proteins, PHT1;11 and PHT1;13 are specifically induced in

arbusculated cells. Both transporters are required for fungal colonization of the root

but only PT11 imported fungus-provided Pi, while the role of PT13 remained elusive.

We found that PT13 is a plasma membrane-localized Pi exporter that is induced in

tissue with strongly elevated Pi concentration, thereby suggesting a role for PT13 in

Pi homeostasis of arbuscule-containing cells.

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ORAL PRESENTATIONS Monday 10 September

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The structural composition of soil phosphomonoesters based on solution 31P NMR spectroscopy with transverse relaxation experiments

Timothy McLaren1, René Verel2, Emmanuel Frossard1

1Department of Environmental Systems Science, ETH Zurich, 8315 Lindau, Switzerland 2Department of Chemistry and Applied Biosciences, ETH Zurich, 8093 Zurich, Switzerland

Keywords: chemical nature, organic phosphorus

The chemical nature of soil organic phosphorus (P) is complex. A large proportion of

the organic P in soil extracts is present as a ‘broad’ signal that underlies the ‘sharp’

signals within the phosphomonoester region of a solution 31P nuclear magnetic

resonance (NMR) spectrum (McLaren et al., 2015). The structural composition of the

broad signal is unknown but could be described as comprising of (i) a series of

neighbouring sharp peaks that merge to visually appear as a broad peak or (ii) one

(or a few) large and complex supra-/macro-molecule. Since the line-width of a

compound is related to its transverse relaxation time (spin-spin relaxation: T2), the

structural composition of NMR signal can be determined with transverse relaxation

experiments. Our aim was to determine the structural composition of soil

phosphomonoesters using solution 31P NMR spectroscopy with transverse relaxation

experiments.

Four diverse soils were sampled from the surface mineral horizon of different

ecosystems. Organic P was extracted with NaOH-EDTA, and then prepared and

analysed by solution 31P NMR spectroscopy with transverse relaxation experiments

using the Carr-Purcell-Meiboom-Gill (CPMG) pulse sequence (Meiboom & Gill, 1958).

Concentrations of extractable organic P ranged from about 200 to 1000 mg/kg across

all soils. Solution 31P NMR spectra revealed the presence of ‘broad’ and ‘sharp’

signals at varying intensities. Transverse relaxation experiments showed that the

broad signal within the phosphomonoester region rapidly decayed compared to that

of the sharp signals (i.e. myo- and scyllo-inositol hexakisphosphate) across all soils,

which corresponded to the former having a shorter transverse (T2) relaxation times

than the latter. Our results demonstrate the existence of a broad signal in the

phosphomonoester region, and that it is structurally comprised of a single (or a few)

supra-/macro-molecular structure.

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Figure 1. A conceptual schematic of the structural composition of the ‘broad’ signal (blue line)

relative to that of the overlying ‘sharp’ signals (myo-IHP (red line) and scyllo-IHP (orange line))

in the phosphomonoester region, based on NMR and transverse relaxation experiments on soil

extracts.

References

- McLaren T, Smernik R, McLaughlin M, McBeath T, Kirby J, Simpson R, Guppy

C, Doolette A, Richardson A (2015) Complex forms of soil organic phosphorus – a

major component of soil phosphorus. Environ. Sci. Technol. 49:13238-13245

- Meiboom S, Gill D (1958) Modified spin-echo method for measuring nuclear

relaxation times. Rev. Sci. Instrum. 29:688-691.

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Availability and chemical nature of phosphorus as influenced by long-

term mineral and organic applications on a nutrient depleted soil F.J.T. van der Bom1, T.I. McLaren2, A.L. Doolette3, J. Magid1, E. Frossard2, A. Oberson2, L.S.

Jensen1 1Plant and Soil Science Section, Department of Plant and Environmental Sciences, Faculty of

Science, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark

Keywords: 33P Isotopic Exchange Kinetics, 31P NMR spectroscopy, P depletion Sustainable use of phosphorus (P) in agriculture requires strategies that make more

efficient use of fertiliser P on low and moderately fertile soils. This research

evaluated the effects of different long-term P fertilisation strategies on a purposely

depleted soil (>30 years). The Long-term Nutrient Depletion Trial (DK) was

established in 1964 on a sandy loam soil. For over 30 years, the field received only

nitrogen containing fertilisers, while Olsen-P concentrations dropped to around 10

mg kg-1 (1995). A long-term fertilisation experiment then commenced in 1996, with

cereals forming the main crop component. Van der Bom et al. (2017) provide further

details. Soils from five treatments were collected in 2016 (kg ha-1 a-1): N1K1 (120N-

0P-120K); N1P1K1 (120N-20P-120K); M1 (112N-27P-88K in the form of animal

slurry); N1P2K2 (N1P1K1 + 20 kg extra mineral P since 2010); M1P1 (M1 + 20 kg extra

mineral P since 2010). Effects on soil P forms and availability were evaluated using

chemical P extractions (Table 1), 33P isotopic exchange kinetics (IEK), and 31P-NMR

spectroscopy on NaOH–EDTA extracts. Olsen-P was closely correlated with the P

budgets, and this was also the case for the amounts of rapidly available P as

determined by IEK (E1min, 1-6 mg kg-1). Between 61% (N1K1) and 77% (N1P2K2) of

total inorganic P was only very slowly exchangeable (E>90days). However, P

exchangeable in a growing season (E90days) was not different between treatments,

suggesting a redistribution of exchangeable P had taken place

Table 1: Twenty-year P budgets and a selection of results from chemical P extractions

Phosphomonoesters and orthophosphate made up in total 98% of the NMR signal,

but only orthophosphate varied between treatments (86 -135 mg kg-1). Microbial P

was double under slurry (18 mg kg-1) compared with NPK (9 mg kg-1).

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Together with existing yield data (e.g. van der Bom et al., 2017), the results indicate

P applications increase the availability of P to the crop under these low-P conditions,

while displaying a high recovery, but that applications exceeding crop demand

mostly increase very slowly exchangeable pools that are unlikely to contribute to

crop availability in following seasons. Differences in microbial P indicate potential for

further investigation into the organic P fluxes.

References - Van der Bom FJT, Magid J, Jensen LS (2017) Long-term P and K fertilisation strategies and balances affect soil availability indices, crop yield depression risk and N use European Journal of Agronomy 86:12–23.

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Exchange times for commonly-considered inorganic soil phosphorus pools

Chiara Pistocchi1*, Julian Helfenstein2*, Astrid Oberson2, Federica Tamburini2, Emmanuel

Frossard2 1Eco&Sols, Montpellier SupAgro, Univ Montpellier, CIRAD, INRA, IRD, 34060 Montpellier, France

2Institute of Agricultural Sciences, ETH Zurich, 8315 Lindau, Switzerland

*the authors contributed equally to this abstract

Keywords: Phosphorus cycling, exchange times, isotope exchange kinetics

Present understanding of phosphorus (P) cycling in soils relies mostly on

measurement of pools while leaving out the temporal component (figure 1). The

most widespread method for studying P pools is a (Hedley) sequential extraction

including bicarbonate, NaOH, and HCl-extractions (Tiessen and Moir, 1993).

However, to date, sequential extractions give no information on kinetics. Here, we

aimed to determine exchange times for inorganic fractions of Hedley pools. We did

so by considering published literature on soils for which both sequential extraction

and radioisotope exchange kinetic data was available. Radioisotope exchange

kinetics allow determining P pools by their time of exchange with the phosphate ions

in solution. Our analyses showed a strong correlation between isotopically

exchangeable pools and Hedley pools for several soil types under different climates

and land uses. The results suggest that the P pool extracted by bicarbonate is

exchanged on the range of hours; NaOH-P on the range of weeks-months; and HCl-

P on the range of months to millennia. A similar approach on sewage sludges gave

similar results (Frossard et al., 1996), but it was never attempted on a broad range

of soils.

Figure 1: exchange processes between phosphate in the solid phase and in the soil solution, modified from Devau et al. Appl. Geochem. 2009.

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These exchange times for commonly-considered inorganic P pools improve our

interpretation of sequential extractions and are important to refine P management

strategies and improve biogeochemical models.

References

- Tiessen H, Moir JO (1993) Characterization of available P by sequential

extraction. In: Soil Sampling and Methods of Analysis. Carter MR, Ann Arbor, pp. 75-

86.

- Frossard E, Sinaj S, Dufour P (1996) Phosphorus in urban sewage sludges as

assessed by isotopic exchange. Soil Science Society of America Journal 60: 179-182

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Silicon effect on soil phosphorus availability under contrasting

agricultural practices

Wissem Hamdi1,2, Jean-Thomas Cornelis3, Aimé-Jean Messiga4, Félix de Tombeur3, Gilles

Colinet3

1. Higher Institute of Water Sciences and Techniques of Gabes, Tunisia

2. Laboratory of Energy and Materials (LABEM), Sousse, Tunisia

3. University of Liege, Gembloux Agro-Bio Tech, TERRA Teaching and Research Centre,

Belgium

4. Agriculture and Agri-Food, Canada

Keywords: silicon, agricultural practices, aggregate

We aimed to study the effect of Si on P availability in bulk soils with similar

pedological conditions but contrasting agricultural management practices.

Compared to conventional practices (CONV), conservation agricultural practices

(CONS; no tillage, direct seeding, no fertilizer input and diverse plant cover) did not

affect total P content. The distribution of P forms is however affected: relatively

higher organic P under CONS practices compared to CONV practices. The results of

P desorption experimentation showed that addition of Si (0, 0.025, 0.05, 0.1, 0.15M)

significantly increased P release in soil solution in bulk soils. The resulting increase of

P concentration in soil solution was +39% in CONS and +33% in CONV, comparing soil

without and with 0.15M Si added in soil solution. The effect of Si is influenced by the

aggregate size fractions. Si ability to solubilize P after 0.15M Si addition was higher

in micro-aggregates compared to other soil fractions: +57% in CONS and +64% in

CONV. We also highlighted that the Si ability to solubilize P was higher in silt/clay

fraction under CONS agricultural practices compared to CONV practices. Our results

therefore demonstrate that Si ability to solubilize P in bulk soils is merely not

dependent on agricultural practices while solubilisation ability in aggregate size

fractions is dependent on agricultural practices. Our desorption isotherms also

demonstrate that, in a soil not deprived in P (available P > 10mg/100g), mechanisms

increasing P availability seem to be partly explained by desorption processes as rates

of P sorption on mineral surfaces is not affected by Si content in solution. Soil

processes affecting P availability after Si addition should be studied in soils

characterized not only by variable agricultural practices but also by contrasting

mineralogical properties.

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Quadrupole Mass Spectrometer Method for the Quantification of Inorganic and Organic Phosphate Species for Applications in 18O- Stable Isotope Probing

Aimée Schryer1, Steven D. Siciliano1, Kris Bradshaw2 1Department of Soil Science, University of Saskatchewan, 51 Campus Drive, Saskatoon,

Saskatchewan, Canada 2Federated Cooperatives Ltd., 401 22nd Street East, Saskatoon, Saskatchewan, Canada

Keywords: Mass spectrometry, stable isotope probing

When Phosphorus (P) fertilizers are added to soils, both the identity of the

microorganisms incorporating the P or into which biological macromolecules is not

known. By using heavy phosphate (P18O(n)) stable isotope probing, one can track

the P as it cycles through the soil and microbial populations. However, methods to

identify P18O(n) incorporation into microbial macromolecules and the optimal times

to incubate samples to track P18O(n) incorporation into DNA are not established.

Soil (10g) microcosms were treated with either: (i) 18O-labelled phosphate, (ii)

unlabelled phosphate or (iii) Milli-Q control, dissolved in a biostimulatory solution

consisting of 0.24 mM HNO3 [3.4 mg/L N], 0.24 mM Fe(III)NH4-citrate [13 mg/L

Fe(III)], 22 mM SO4 [700 mg/L S]) and 0.1 mM P-species (3.1 mg/L P) at a

circumneutral pH. Microcosms were sampled for both total P via sequential

extraction and DNA. Double stranded DNA samples are digested to their respective

3’-deoxynucleoside 5’-monophosphates (dNMP). The collision-induced dissociation

(CID) tandem mass spectrometric (MS/MS) analysis of each P-species was conducted

using a QTRAP® 4000 LC/MS/MS system attached to an Agilent 1200 Series HPLC

System. The MS/MS, a hybrid triple quadrupole–linear ion trap mass spectrometer

(QqQ-LIT), is equipped with a 'Turbo V Ion Spray' ESI source where nitrogen was

utilized as the collision gas. Phosphorus extracted from resin anion exchange strips

was measured on the MS/MS and compared with the SEAL AutoAnalyzer 3 HR (AA3)

to determine if results are comparable (Fig 1 and 2).

Results show that isotopic composition does not have a significant effect upon the

microbial uptake of the orthophosphate or precipitation reactions with soil. A mass

balance equation will determine total P within the microcosms. Overall, using the

MS/MS method in SIP experiments will allow anthropogenic P to be followed within

ecosystems to better understand soil activity.

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Figure 1 and 2: Resin extractable 16O- and 18O- orthophosphate by week. Control microcosms had low 16O-orthophosphate concentrations whereas no 18O-orthophosphate was measured outside of labelled microcosms.

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Phosphorus availability for crops in a soil P depleting scenario

Nawara Sophie1, Amery Fien2, Merckx Roel1, Smolders Erik1

1 Division of Soil and Water Management, Department of Earth and Environmental Sciences, KU

Leuven, Kasteelpark Arenberg 20 bus 2459, 3001 Leuven, Belgium.

Keywords: Depletion scenario, phosphorus availability, crop growth rate.

The imbalance between phosphorus (P) input (P fertilization) and crop P offtake

during the last decades caused an accumulation of phosphorus in agricultural soils.

Due to more sustainable and more strict P fertilizer use, the soil P balance has turned

negative in some European regions (depletion). It is expected that the availability in

a P depleting scenario is smaller than in a P accumulation scenario due to the

hysteresis of the sorption-desorption processes. In this study, the effect of P uptake

rate on the availability of P in a depleting scenario is evaluated. To address this we

(i) set up an accelerated soil P mining test and (ii) modelled the availability of

phosphorus in a P depleting scenario.

(i) Perennial ryegrass was grown for two years in a greenhouse on 5-cm deep

soil layers of eight contrasting soils with periodic grass clipping. Each soil was split in

2 x 2 fertilizer treatments, i.e. no P (–P) and adequate P (+P) and two nitrogen levels,

the latter to alter the P uptake rate. The long-term P mining induced P-related yield

losses in seven of the 16 soils (8 soils x 2 N treatments). The critical cumulative uptake

of shoot P (CCP) at which yield loss started to exceed 10% (–P versus +P) varied over

a small range of 37–74 mg P kg-1 soil among soils. Increased N supply accelerated

growth and rates of P uptake and decreased the CCP by, on average, a factor 1.7,

illustrating the effect of the growth rate on P deficiency.

(ii) The model combines the soil P supply to the plant roots and the plant P

demand rate. The soil solid phase is subdivided into 2 pools: a labile solid phase pool

which rapidly replenishes the P in soil solution and a fixated solid phase pool which

only slowly replenishes the labile pool, i.e. upon depletion the resupply of the P in

soil solution is controlled by the desorption kinetics of both pools. The model is used

to determine the effect of the crop growth rate (for example: wheat, maize and

potato) and the effect of P depletion, i.e. a decreasing ratio of the labile to the fixated

solid phase pool, on the availability of P for plants.

This study showed, by experimental analysis and by modelling, that upon depletion

the phosphorus availability to plants decreases. Moreover the plant growth rate has

been shown to be a critical factor in determining whether and when P deficiency

occurs in a P depleting scenario.

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Capturing land surface feedback by Landsat-8 to estimate soil phosphate

absorption capacity under Andisols of Hokkaido, Japan

Rintaro Kinoshita1, Murray Clayton2, Masayuki Tani1 1 Research Center for Global Agromedicine, Obihiro University of Agriculture and Veterinary

Medicine, Obihiro, Hokkaido 080-8555, Japan.

Keywords: Andisols, phosphate, remote sensing

Adequate phosphate fertilizer application is crucial for maintaining high crop yields

in Andisols but also for sustainable use of phosphate reserve. In our previous study

in a 15-ha arable field of Hokkaido, Japan, we discovered a huge spatial variation of

soil available phosphate (39.0～482 mg kg-1), and it was highly correlated with

phosphate absorption coefficient (PAC; r = -0.78), a Japanese soil testing method for

phosphate retention. This signified the importance of varying phosphate application

rates adjusted to the soil PAC levels, however, manual soil sampling and analysis are

costly and unfeasible. Therefore, this study was conducted to develop a novel

approach to spatially estimate the PAC using remote sensing information.

Eighty surface soil samples were collected from a 15-ha arable field of Hokkaido,

Japan. We assessed PAC, soil available phosphate, total carbon as well as

sequentially extractable aluminum (Al), iron (Fe), and silica (Si) using acid ammonium

oxalate and sodium pyrophosphate. The Landsat-8 image was acquired when the soil

surface was bare and the soil moisture content was low (May 2015). We used a

linear-regression model for the estimation of PAC.

We identified a high correlation between PAC and Al extracted by acid ammonium

oxalate, indicating that PAC is related to both Al from 1) Al-humus complex and 2)

non- and para-crystalline aluminosilicates. A near infrared band of Landsat-8 was

successful in predicting total C that is related to Al-humus complex, but could not

estimate the variation of the non-crystalline aluminosilicates. Therefore, we

evaluated the use of soil moisture holding capacity at -1500 kPa as a proxy for

specific surface area of the soil, and we found a very strong positive correlation with

PAC (r = 0.88; Figure 1). The short-wave infrared band (2.107-2.294 μm) of Landsat-

8 is known to be sensitive to soil moisture variation, and we found the predictability

of PAC at R2 = 0.55 and RMSE = 233 (Figure 2). Therefore, this study revealed the

existence of a strong positive correlation between moisture holding capacity of the

soil and PAC as well as introducing a concept of capturing land surface soil moisture

feedback by remote sensing to indirectly estimate PAC under Andisols.

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tim

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15

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r c

on

ten

t (%

)

Phosphate absorption coefficient

Measu

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Esti

mate

d

Ph

osp

hate

Ab

so

rpti

on

Co

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icie

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50

11

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Fig

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Fig

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2

)

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Evolution of soil P over time as function of the cumulative soil P

balance: how can we close the gap?

Fien Amery1, Bart Vandecasteele1, Tommy D’Hose1, Wendy Odeurs2, Annemie Elsen2, Hilde

Vandendriessche2, Christian Roisin3, Steve McGrath4, Mathias Cougnon5, Sophie Nawara6, Erik

Smolders7 1Institute for Agricultural and Fisheries Research, Plant Sciences Unit - Crop Husbandry and

Environment, Burgemeester Van Gansberghelaan 109, 9820 Merelbeke, Belgium

Keywords: Soil P balance, ammonium lactate extraction

Soil P status differs widely among agricultural soils in Europe. Ideally, soil P evolves

towards a target zone for soil P, i.e. sufficient P for the crop but not too high to

prevent environmental P losses. This requires information on the extent of soil P

changes induced by net positive and negative soil P balances. In Flanders, Sweden,

Norway, The Netherlands and Hungary soil P is measured as P-AL (P extracted with

ammonium lactate at pH 3.75, Egnér et al, 1960). Data were gathered from 34 multi-

year field experiments (4-51 years), both from literature and our own experiments.

P-AL was measured in the beginning and end of the different (mostly P fertilization)

treatments of the experiments. Changes of P-AL in time were related to the

cumulative soil P balance or net P dose, i.e. input of P by fertilization minus output

of P by crop offtakes.

Partial results (all data will be available at the conference) indicate that on average

more than 70% of the net P dose is not recovered in the P-AL fraction of the top soil

(Figure 1). Surprisingly, in treatments with net negative soil P balance also 70% of P

offtakes by crops are not registered by P-AL changes in soil. Although AL is a rather

harsh extraction (P-AL ≈ 2-4 * P-Olsen), most of the P active in the plant-soil cycle is

not accounted for in the P-AL fraction. Additional analyses on soil of three field

experiments show that also by total soil destruction, more than half of the net P dose

is not recovered from the top layer (0-23/25 cm), indicating that a significant part of

the net P dose is taken up from or leached to the deeper soil layers. Multiple

regression will be used to analyze the importance of the initial value of P-AL and soil

characteristics (e.g. pH, Fe and Al content, organic matter content) on the evolution

of P-AL in time. Partial results show that at equilibrium fertilization (soil P balance =

0), P-AL decreases on average by 1.6 mg P kg-1 y-1.

Information on evolution of P-AL can contribute to sound P advice in order to evolve

towards target P-AL values.

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Figure 1: Change in P-AL by the cumulative soil P balance from 34 field experiments

References

- Egnér H, Riehm H, Domingo WR (1960) Untersuchungen über die

chemische Bodenanalyse als Grundlage für die Beurteilung des Nährstoffzustandes

der Böden. II. Chemische Extraktionsmethoden zur Phosphor- und

Kaliumbestimmung. Kungliga Lantbrukshögskolans 26: 199-215.

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Microbial loop efficiency: is the bacterial group and/or phytase type a

key element enhancing P mobilization from phytate?

Mercedes García-Sánchez, Mathilde Souche, Jean-Jacques Drevon, Carlos Trives-Segura,

Claude Plassard

INRA, UMR Eco&Sols, 2, Place P. Viala, F-34060-Montpellier, France

Keywords: Bacterial feeding nematodes, phytase-producing bacteria, phytate

mineralization.

Bacteria are important for mineralizing some recalcitrant forms of organic

phosphorous (P) in soils such as phytate through phytase production. Therefore,

phytate might represent an alternative Pi source for plants due to its low mobility

and high capacity to forms complexes with cations. The nematofauna is an important

component of soil biodiversity driving the nutrient cycling and plant mineral

nutrition (Trap et al., 2016). In contrast to N cycling, our knowledge in P cycling from

phytate is very limited. The nematodes feeding on bacteria (microbial loop) might

represent a key strategy to release free Pi from microbial biomass to increase its

uptake by plants. However, so far, the mechanisms governing the bacterial predation

of nematodes are scarcely understood. The objective of this study was to evaluate

the capacity of nematodes (Acrobeloides sp.) to feed on gram negative

(Bradyrhizobium sp.) or positive (Bacillus subtilis 168) able to use phytate as the sole

source of P. However, Bradirhizobium sp. has an intracellular phytase whereas B.

subtilis 168 produce an extracellular phytase. We designed a microcosms system

made of small Petri dishes (35 mm × 15 mm) filled with agarose base medium

supplied with phytate or Pi (1mM), whether or not inoculated with bacteria (Irshad

et al., 2012). They were placed in a large square Petri dish (12 cm × 12 cm) which was

filled with agarose and Pi and 100 nematodes were inoculated at the bottom. The

dishes were collected weekly up to 3 weeks to measure the nematode and bacterial

populations and the pools of Pi contained in bacteria, nematode and agarose. This

experiment allowed us to decipher if the microbial loop efficiency depends on

bacterial group and/or the capacity of bacteria to mobilize the Pi from phytate.

References

- Irshad U, Brauman A, Villenave C, Plassard C 2012. Phosphorus acquisition

from phytate depends on efficient bacterial grazing, irrespective of the mycorrhizal

status of Pinus pinaster. Plant and Soil 358: 155–168.

- Trap J, Bonkowski M, Plassard C, Villenave C, Blanchart E 2016. Ecological

importance of soil bacterivores for ecosystem functions. Plant and Soil 398: 1–24.

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In-soil trophic interactions between plants, rhizosphere bacteria and

nematodes:

Improving availability of organic phosphorus

Malika Mezeli1, Tim S. George2, Roy Neilson2, Martin S.A. Blackwell3, Phil M. Haygarth1 1Lancaster Environment Centre, Lancaster University, Bailrigg, LA1 4YW

2Ecological Sciences, The James Hutton Institute, Dundee, DD4 5DA 3Sustainable Agricultural Systems, Rothamsted Research, North Wyke, EX20 2SB

Keywords: Organic phosphorus, phytase, nematodes

Significant disparities between phosphorus (P) fertiliser application and plant P

uptake, is in part induced by the in-soil conversion of inorganic P (Pi) to organic P

forms (Po), which are not readily plant available. Phytase enzymes released by

certain plants, bacteria and fungi hydrolyse organic sources (eg: InsP1-6) to plant

available forms. Recent experimental work and historical ecological observations has

demonstrated that bacterivorous nematodes can be complementary to plant P

uptake, indicative of beneficial trophic interactions. The project aim is to

demonstrate this beneficial interaction in arable cropping systems by investigating

two main questions: (1) Do nematodes increase plant acquisition of InsP6 hydrolysed

by phytase producing bacteria in arable systems? and (2) What are the key

mechanisms behind such plant responses?

Barley plants were grown under sterile conditions in agar with three different P

treatments (no P, Pi and InsP6), phytase producing bacteria (Pseudomonas sp.,

CCAR59) and bacterivorous nematodes (Caenorhabditis elegans). Biomass

accumulation and plant P concentrations suggested that beneficial trophic

interactions were induced only under significantly P deplete systems, however the

data failed to provide statistically significant results.When repeated in grassland soil,

with a low Pi and high Po profile, a significant effect of nematodes was observed in

the +InsP6 treatment. The data from these trials suggest that although a P deplete

system is required to observe beneficial trophic interactions, a baseline of P is

required to kick-start these bio-chemical functions, provided here by the +InsP6. In

addition, in the agar trials, plant roots were able to colonise the entirety of the

substrate, thereby potentially masking treatment effects due to the possible role

nematode mobility and exploration may play in such biochemical transformations

and measured plant responses. Therefore, later trials were conducted in agar

without plants and conversion rates of InsP6 to Pi per mm of nematode exploration

was measured. Such studies will allow for a better understanding of the role

nematodes have, as an additional trophic cascade, on the P cycle in arable systems

and bring together ecological functions to improve agronomic practice.

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Arbuscular mycorrhizal fungi stimulate organic phosphate mobilization

associated with changing bacterial community structure under field conditions

Lin Zhang1, Ning Shi1, 2, Fei Wang1, Timothy S. George3, Gu Feng1

1College of Resources and Environmental Sciences, China Agricultural University,

100193,Beijing, China 2Institute of Agricultural Resources and Environment, Shandong Academy of Agricultural

Sciences, 250100, Jinan, China 3The James Hutton Institute, Invergowrie, Dundee, DD2 5DA, UK

Key words: Alkaline phosphatase, Hyphosphere microbiome, Mycorrhizal pathway, Soil bacteria The extraradical hyphae of arbuscular mycorrhizal fungi (AMF) harbor and interact

with a microbial community performing multiple functions. However, how the AMF-

microbiome interaction influences the phosphorus (P) acquisition efficiency of the

mycorrhizal pathway is unclear. Here we investigated whether AMF and their hyphal

microbiome play a role in promoting organic phosphorus (P) mineralizing in situ

under field conditions(Fig.1).

We developed an AMF hyphae in-growth core system for the field by using PVC tubes

sealed with membrane with different size of pore (30 or 0.45 μm) to allow or deny

AMF hyphae access to a patch of organic P (i.e., phytate) in root-free soil. Arbuscular

mycorrhizal fungi and their hyphae associated microbiome played a role in

enhancing soil organic P mineralization in situ in the field, which was shown to be a

function of the change in bacteria community on the hyphae surface.

The bacterial communities attached to the AMF hyphae surface were significantly

different from those in the bulk soil. Importantly, AMF hyphae recruited bacteria

that produced alkaline phosphatase and provided a function that was absent from

the hyphae. These results demonstrate the importance of understanding trophic

interactions to be able to gain insight into the functional controls of nutrient cycles

in the rhizosphere.

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Days after sowing

Δ P

i (m

g k

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-25

-20

-15

-10

-5

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5

Maize, -Phytate

Maize, +Phytate

Soybean, -Phytate

Soybean, +Phytate

Days after sowing

Δ A

LP

(pK

atal

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soil

)

-30

-20

-10

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10

20

(a) (b)

45 75 105 45 75 105

Δ P

hy

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-P (

mg k

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-15

-10

-5

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-Phytate

+Phytate

Maize Soybean

Δ P

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atal

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soil

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0

100

200

300

400

Maize Soybean

a

b

a

ba

b

a

b

* *

(c)

(d)

Fig.1 Difference of P contents and phosphatase activities in the in-growth tubes buried in maize and soybean fields with and without the presence of AMF. (a) Inorganic P and (b) alkaline phosphatase activity harvest at 45, 75 and 105 days after sowing. (c) Phytate-P (d) and phytase activity in cores at 105 days after sowing. Data are means (n = 3) + standard error. Different letters indicate significant difference between two phytate treatments of the same crop species (P ≤ 0.05). The asterisk indicates significant difference between two crop species at the same phytate treatment.

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The root external mycelium of mycorrhizal fungi has a key role in plant P uptake

but is suppressed by soil microbiota.

Carla Cruz-Paredes1, Nanna B. Svenningsen, Stephanie Watts-Williams, Fabio Battini, Erik J

Joner, Majbrit Dela Cruz, Jan C. Christensen, Ole Nybroe, Iver Jakobsen 1University of Copenhagen, Department of Plant and Environmental Sciences, Frederiksberg,

1871, Denmark

Keywords: Arbuscular mycorrhizal fungi, microbiota

Arbuscular mycorrhizal fungi (AMF) form a symbiotic association with approximately

80% of all known terrestrial plant species including agricultural crop species. In this

association, the fungus obtains carbohydrates from the plant and in exchange, plants

acquire inorganic nutrients through the fungal mycelium (Smith and Read 2008). The

role of AMF is most remarkable under phosphorus (P) limiting conditions where

mycorrhiza-mediated P uptake can result in large plant growth responses. Early

reports suggested that the activity of AMF can be suppressed in non-sterile soils

(Hetrick et al. 1988), resembling the phenomenon of ‘disease suppressive soils’

(Weller et al. 2002). Microbial groups and metabolites responsible for suppression

of other fungi have been identified (Cha et al. 2016), while organisms and

metabolites suppressive towards AMF are unknown. This study aims to assess

whether suppression of the AMF by unsterile soil is common, its causes, and the

degree of resistance in different AMF strains.

Suppression of AMF by unsterile soils was investigated in a Medicago truncatula

model system with 33P-labelled patches of soil where patches were accessible by

AMF hyphae, but not roots. 33P uptake into shoots was used as a proxy for AMF

activity. A range of different soils were screened and effects of liming and

pasteurization were determined for suppressive soils. Additionally, microbiome

profiles from the different soils were assessed by 16S-rRNA sequencing and

compared to data of 33P uptake. Finally, resistance to suppression in different strains

of AMF was assessed.

We found a large variation in AMF suppression across different soils. A clear pattern

of pH was found where suppression was greater at low than at high pH. AMF

suppression was noticeably mitigated by soil pasteurization or liming. PCA analysis

of 16S-rRNA amplicon sequencing data revealed a clear separation between

microbiomes found in AMF suppressive and non- suppressive soils. Acidobacteria

subgroup 1 was more abundant in suppressive soils and may be a potential AMF

suppressor (Svenningsen et al. 2018). We also found that degree of suppression

depended on the AMF strain.

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It is clear that AMF suppression has a biotic component of origin. Ongoing work aims

to identify and isolate AMF suppressive microorganisms and to identify the

metabolites responsible for this suppression. The perspective is to develop new field

management strategies for improving the role of AMF in plant nutrition.

References

- Cha JY, Han S, Hong HJ, et al (2016) Microbial and biochemical basis of a

Fusarium wilt-suppressive soil. ISME J 10:119–129.

- Hetrick BAD, Wilson GT, kitt DG, Schwab AP (1988) Effects of soil

microorganisms on mycorrhizal contribution to growth of big bluestem grass in non-

sterile soil. Soil Biol Biochem 20:501–507.

- Smith S, Read D (2008) Mycorrhizal symbiosis, 3rd edn. Elsevier Ltd, London,

UK.

- Svenningsen NB, Watts-Williams SJ, Joner EJ, et al (2018) Suppression of the

activity of arbuscular mycorrhizal fungi by the soil microbiota. ISME J 12:1296–1307.

- Weller DM, Raaijmakers JM, Gardener BBM, Thomashow LS (2002)

Microbial populations responsible for specific soil suppressiveness to plant

pathogens. Annu Rev Phytopathol 40:309–348.

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Characterization of LaMATE-PI1, a candidate of citrate transporter isolated

from cluster roots of white lupin.

Hiroaki Furutani1, Kiyotoshi Hanashiro1, Yumi Fujii1, Hayato Maruyama2, Takayuki Sasaki3, Jun

Wasaki1

1Graduate School of Biosphere Science, Hiroshima Univ., Kagamiyama 1-7-1, Higashi-Hiroshima

739-8521, Japan; 2Research Faculty of Agriculture, Hokkaido Univ., Japan; 3Institute of Plant

Science and Resources, Okayama Univ., Japan.

Keywords: White lupin, citrate transporter, cluster root

White lupin (Lupinus albus L.) has developed strategies to adopt low phosphate (P)

condition in soils by forming cluster roots. The cluster roots secrete a large amount

of citrate to solubilize P in soils under P deficiency (Gardner et al. 1983). Some

exudations such as isoflavonoids are secreted to decrease microbial consumptions

of carboxylates by modification of microbial community structures. It has been

proposed that citrate channel plays an important role to release citrate from cluster

roots (Zhang et al. 2004), although the citrate transporter/channel has not been

isolated yet. This study aimed to characterize a candidate of citrate transporter

isolated from cluster roots of white lupin. It was shown that both P-deficiency and Al

stress stimulated citrate exudation from whole roots of white lupin (Fig.1),

suggesting that the pathway of citrate exudation is different between these stresses.

We isolated a cDNA for a homolog of MATE (multidrug and toxin extrusion) type

transporter, designated as LaMATE-PI1, from cluster roots of white lupin. The

deduced amino acid sequence of LaMATE-PI1 has similarity to MATE-type

transporters such as MtMATE56, and AtMATE2, which is induced by P deficiency, but

shows different clade which includes citrate transporters induced by Al stress or Fe

deficiency (HvAACT1, OsFRD1, and AtMATE). SOSUI program presumed that

LaMATE-PI1 contained 12 transmembrane domains. mRNA for LaMATE-PI1 was

increased under P deficiency at cluster root specifically, and not altered by Al stress

(Fig.2). These results are consistent with a hypothesis that LaMATE-PI1 plays an

important role in releasing abundant amount of exudation from cluster roots of

white lupin under P-deficiency.

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References

- Gardner WK, Barber DA, Parbery DG (1983) The probable mechanism by

which phosphorus movement in the soil/root interface is enhanced. Plant and Soil 70:

107-124.

- Zhang WH, Ryan PR, Tyerman, SD (2004) Citrate-permeable channels in the

plasma membrane of cluster roots from white lupin. Plant Physiology 136: 3771-3783.

Fig.1 Citrate exudation under +/-P and +/-Al condition

Fig.2 Relative expression of LaMATE-PI1 under +/-P and/or +/-Al condition. R: Whole Root, NR: Normal Root, CR: Cluster Root.

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Accumulation, transformation and distribution of phosphorus in soil profile as affected by long-term P fertilization on calcareous soils (108)

Licun Zhang1, 2, Jiajie Chen1, Baowei Hu2, Gu Feng3, Guixin Chu1, 2*

1 Department of Resources and Environmental Science, Shihezi University, Shihezi, 832003, P. R. China.

2 College of Life Science, Shaoxing University, Zhejiang, 312000, P. R. China.

3 Department of Resources and Environmental Science, China Agriculture University, Beijing, 100220, P. R. China.

Keywords: Olsen-P, transformation, long-term fertilization

In order to explore soil P distribution, transformation and P fertility long-term evolution, literature published from 1981-2013 was collected via the Chinese National Knowledge Infrastructure Database (CNKI, http://www.cnki.net/), and fifteen pairs of soil samples were analyzed using sequential P fractionation method. Soil Olsen-P concentration in 0-20 cm layer significantly increased from 7.2 to 25.9 mg kg-1, which linearly correlated with the10-fold increase of P application rate over 33 years, but soil total P increased slightly. Compared with uncultivated land, higher Olsen-P and total P were observed in 0-30 cm rather than 30-60 cm depth of cropland, suggesting that soil P in topsoil was more susceptible than that in subsoil to P fertilization. Moreover, the decrease magnitudes of labile and moderately labile P in cropland in 0-30 cm depth were greater than those in uncultivated land. The average ratio of the inorganic P fraction in cropland to those in uncultivated land in 0-60 cm depth followed the order of: NaHCO3-P (1.47) > NaOH-P (1.38) > resin-P (1.37) > residue-P (1.17) > HCl-P (1.11), indicated that the applied-P contributed more to the increase in labile and moderately labile forms. PCA analysis showed that cropland was distinctly differentiated from uncultivated land in topsoil (0-30 cm) in terms of the variations of Olsen-P (0.737), total P (0.674), resin-P (0.738) and NaHCO3 (0.686). Overall, reduction P fertilization rate is strongly recommended by exploiting the topsoil P legacy, especially utilizing the labile and moderately labile P which mainly derived from long-term P fertilization in calcareous soils.

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Figure 1: Layout of the accumulation, transformation and distribution of phosphorus in soil profile.

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Phosphorus Status in the Calcareous Soils and Wheat of Iraqi Kurdistan

Muhammed S. Rasheed1, 2, Scott D. Young1, Elizabeth H. Bailey1

1Division of Agriculture and Environmental Science, University of Nottingham 2Technical College of Applied Science, Halabja, Sulaimani Polytechnic University

Keywords: Phosphorus, soil, wheat grain, phytic acid There are no widespread data for phosphorus (P) and phytic acid (PA), in soil and wheat, from the Kurdistan region of Iraq. Phytate is important when evaluating the P status of food crops and wheat is the staple carbohydrate source for the region. In the present study, 120 farmers’ fields were sampled for soil and wheat grain. The soil samples were analyzed for total, available and soluble phosphorus (PTot, POlsen, and PSol) and the solid-liquid partition coefficient (Kd). At harvest, values (mg kg-1) ranged between 403-3740 for PTot, and 2.13-28.1 for POlsen. PSol was ranged between 0.07-9.91 mg L-1. Moreover, the partition coefficient of P between solid and solution phases (Kd= POlsen/PSol) was also investigated. The values of log (Kd) were in the range 0.12-2.13, indicating low adsorption of P due to low available P in the soils. Soil pH was in the range 7.46-8.67 indicating that all the soils were calcareous. However, about 83% of soil samples contained a low amount of available P and 53% contained a low amount of soluble P, below-recommended values of 15 mg kg-1 POlsen and 0.5 mg L-1 PSol. This may be due to the relatively high CaCO3 content and high pH values of these soils. On the other hand, the values of P and PA concentrations (mg kg-1) in wheat were 2000-4600 (P) and 3000-11,000 (PA) indicating that 7.3% of the wheat grain total weight was PA and about 64% of P was present as PA. The results suggest that the concentration of P and PA is high, about 40% of wheat grains contain higher amounts than the recommended value of 3570 mg kg-1 of P (USDA Food Composition Databases). The PA concentration of 64% of wheat grains contains higher amounts than reported value for whole wheat grain flour 6750 mg kg-1 of PA (Magallanes-Lopez et al. 2017). These are probably due to extensive applications of phosphate fertilizers by farmers, typically 100 - 200 kg P2O5 ha-1 in every growing season. Our results suggest that soil Olsen-P status management could be an effective agronomic tool to improve wheat grain P and PA concentrations while understanding the environmental impact is essential in determining the impact of agriculture management and P status in wheat production in the region.

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Estimating oxalate P of paddy soils in Madagascar using Vis-NIR reflectance

spectroscopy

Andry Andriamananjara1, Kensuke Kawamura2, Michel Rabenarivo1, Hidetoshi Asai2, Tovohery Rakotoson1, Yasuhiro Tsujimoto2

1Laboratoire des Radio-Isotopes, Université d'Antananarivo, BP 3383, Route d'Andraisoro, 101 Antananarivo, Madagascar

2Japan International Research Center for Agricultural Sciences (JIRCAS), 1-1 Ohwashi, Tsukuba, Ibaraki 305-8686, Japan

Keywords: Partial least squares regression, soil fertility, waveband selection

The accessibility of standard soil laboratory analyses, which are time-consuming and expensive, remains a challenge for large sample numbers in developing countries. Timely and accurate estimation of soil P availability is necessary for fine-tuning fertilizer management practice in order to alleviate P deficiency and increase crop production in highly weathered soils. Therefore, the development of a low-cost, rapid and reproducible innovative method for soil available P is required both for the scientific community and the smallholder farmers. This study aimed to investigate how soil P can be predicted using laboratory visible- and near-infrared (Vis-NIR) spectroscopy by testing the performance of genetic algorithm PLS (GA-PLS) regression analyses compared to iterative stepwise elimination PLS (ISE-PLS) and standard full-spectrum PLS (FS-PLS). Soil samples (n = 103) from lowland and upland rice fields (0-20 cm of depth) in the central highlands of Madagascar were analyzed for laboratory soil reflectance and oxalate-extractable P. Results of calibration models with cross-validation showed that FS-PLS regression with intermediate prediction ability of oxalate P (RPD = 1.77) could be improved by ISE-PLS and GA-PLS with good prediction ability (RPD > 2.0). The predictive abilities of models were further evaluated using a modified bootstrap procedure. Here, GA-PLS model showed the best prediction performance with the highest coefficient of determination (R2 = 0.79) and lowest root mean square error of prediction (RMSEP = 149) values compared to other models, suggesting that oxalate P in paddy soils in the central highland of Madagascar can be estimated using GA-PLS regression. The selected wavelength regions in GA-PLS and ISE-PLS models were revealed from all available 2001 wavebands over the 400-2400 nm which were relevant for predicting soil oxalate P. The performance of this innovative approach opens a new way for planning sustainable agriculture development of Madagascar and will be applied in the estimation of soils properties in agroecosystems of Madagascar for the characterization of soil fertility and the potential of climate change mitigation in future.

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Soil phosphorus fluxes as affected by drying-rewetting: a dual isotopic study Julian Helfenstein1, Emmanuel Frossard1, Chiara Pistocchi2, Oliver Chadwick3, Peter Vitousek4,

Federica Tamburini1 1Institute of Agricultural Sciences, ETH Zurich, 8315 Lindau, Switzerland

2Eco&Sols, Montpellier SupAgro, Univ Montpellier, CIRAD, INRA, IRD, 34060 Montpellier, France 3 Department of Geography, University of California, Santa Barbara, CA 93106, USA

4 Department of Biology, Stanford University, Stanford, CA 94305, USA

Keywords: Stable oxygen isotope in phosphate, fluxes, processes Drying-rewetting is an inherently important feature of soil behaviour. There has been a lot of research on wetting and drying pulsing, microbial response, and associated nitrogen dynamics. Due to methodological limitations, much less is known about impacts on phosphorus (P) fluxes. Here, we used a novel dual isotopic approach to determine the effect of drying-rewetting on P fluxes and underlying mechanisms in soils from different climate zones. We used soils from a climatic gradient, the well-studied Kohala gradient on Hawaii, in order to test how much the response depends on climatic history. Soils were labelled with 33P and 18O-enriched water, and exposed to drying-rewetting over the course of 6 months. We measured changes in P pool concentrations (resin P, microbial P, NaOH inorganic P, NaOH organic P, and HCl P), as well as incorporation of 33P into these pools with time. Incorporation of 33P into different pools provided insights on ongoing fluxes. Furthermore, stable oxygen isotopic ratios in phosphate were measured to reveal if observed fluxes were driven by physicochemical or biological mechanisms. These results will help to elucidate the effect of drying-rewetting on P dynamics in soils of different climates, which is crucial to improve nutrient management and modelling efforts.

Figure 1. Schematic representation of the drying-rewetting incubation experiment, using soils from a Hawaiian climatic gradient.

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Combining Diffusive Gradients in Thin films (DGT) and spectroscopic techniques for the determination of phosphorus species in soils

Christian Vogel1, Ryo Sekine2,3, Daniel Steckenmesser4, Enzo Lombi3, Hannes Herzel1, Lucia Zuin5, Dongniu Wang5, Roberto Félix6, Christian Adam1

1Division 4.4 Thermochemical Residues Treatment and Resource Recovery, Bundesanstalt für Materialforschung und -prüfung, Unter den Eichen 87, 12205 Berlin, Germany

2Centre for Ecology & Hydrology, Maclean Building, Benson Lane, Crowmarsh Gifford, Wallingford, Oxfordshire OX10 8BB, United Kingdom

3Future Industries Institute, University of South Australia, Building X, Mawson Lakes, SA 5095, Australia

4Institute of Plant Nutrition, Research Center for Biosystems, Land Use and Nutrition, Justus-Liebig University Giessen, Heinrich-Buff-Ring 26-32, 35392 Giessen, Germany

5Canadian Light Source, 44 Innovation Boulevard, Saskatoon, SK S7N 2V3, Canada 6Renewable Energy, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Hahn-

Meitner-Platz 1, 14109 Berlin, Germany

Keywords: Soil P species, spectroscopy, DGT A wide range of methods are used to estimate the plant-availability of soil phosphorus (P). Published research has shown that the diffusive gradients in thin films (DGT) technique has a superior correlation to plant-available P in soils compared to standard chemical extraction tests. In order to identify the plant-available soil P species, we combined DGT with infrared and P K- and L-edge X-ray adsorption near-edge structure (XANES) spectroscopy (see Fig. 1).

Figure 1: Principle of soil P analysis

This was achieved by spectroscopically investigating the dried binding layer of DGT devices after soil deployment. All three spectroscopic methods were able to distinguish between different kinds of phosphates (poly-, trimeta-, pyro- and orthophosphate) on the DGT binding layer. However, infrared spectroscopy was most sensitive to distinguish between different types of adsorbed inorganic and organic phosphates. Additionally, also intermediates of the time-resolved hydrolysis of trimetaphosphate in soil could be analyzed. Furthermore, infrared and XANES microspectroscopy make it also possible to analyze P compounds on the binding layer with a lateral resolution down to 1 µm2. Therefore, P species of a spatial soil segment (e.g. rhizosphere) can be mapped and analyzed.

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In-situ phosphorus availability in soils: long–term ion-exchange resin study

Karolina Tahovská1, Petr Čapek1, Jiří Kaňa2, Hana Šantrůčková1, Jiří Kopáček2 1Faculty of Science, Department of Ecosystem Biology & SoWa, University of South Bohemia,

Branišovská 31, 370 05 České Budějovice, Czech Republic, tahovska@centrum.cz 2Biology Centre of the AS CR, Institute of Hydrobiology, Na Sádkách 7, 370 05 České Budějovice,

Czech Republic

Keywords: P availability, exchange resin, forest soil Phosphorus (P) availability in soils is commonly estimated using extraction methods. Their main disadvantage is the mobilization of even stable and poorly defined soil P fractions and overestimation of bioavailable P. This shortcoming is minimized by use of in-situ iron-based ion exchange resin (IER) that continually removes phosphate from soil solution as an almost „infinite“ sink. We tested suitability of hydrous Fe-oxide nanoparticles based IER (Layne, USA) for measuring P availability in field.1 Then, we used this technique to measure P dynamics in soils of two catchments differing in bedrock (P-poor mica-schist and P-rich granite) during ten consecutive years. The granitic catchment has lower pools of Al- and Fe-hydroxide, lower P adsorbing ability, and higher terrestrial P export to waters. In contrast, soils in the mica-schist catchment accumulate P from deposition in the long-term. Even though both catchments showed substantial P retention (>95% of P inputs), with available P largely exceeding terrestrial P exports, we observed higher P availability in the organo-mineral horizons in the granitic catchment. The observed P availability was thus positively related to the terrestrial P export and negatively to the P adsorbing ability of soils. The variation in P availability was mainly controlled by abiotic factors (throughfall chemistry, precipitation amount, and litter C:P). Nevertheless, we assume that high losses of P in the granitic catchment can also be driven by microbial processes since decomposition activity was the most influential variable of available P there. In conclusion, we advocate IER method as a simple tool and powerful predictor of P losses from various soils. It could be especially valuable in cases when site-specific conditions can disqualify the use of lysimeters or determining of P exports using mass budget studies.

References 1 Tahovská K, Čapek P, Šantrůčková H, Kaňa J, Kopáček J (2016) Measurement of in situ phosphorus availability in acidified soils using iron-infused resin. Commun. Soil Sci. Plant Anal. 47(4): 487–494.

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P uptake of rice plants are highly related to the soil P forms and oxalate-extractable Al and Fe in the typical P-deficient soils of

Madagascar Tomohiro Nishigaki1, Yasuhiro Tsujimoto1, Seheno Rinasoa2, Tovohery Rakotoson2, Andry

Andriamananjara2, Tantely Razafimbelo2 1Crop, Livestock and Environment Division, Japan International Research Center for Agricultural

Sciences, 1-1 Owashi, Tsukuba, Ibaraki, Japan 305-8686 2Laboratoire des Radio-Isotopes, Université d'Antananarivo, BP 3383, Route d'Andraisoro, 101

Antananarivo, Madagascar

Keywords: Available P, Soil P fractionation Soil phosphorus (P) is the most limiting factor for crop production in tropical agroecosystems on strongly weathered soils. However, there is a limited information on soil P availability in relation to P forms, and P use efficiency in rice croplands in Madagascar. The objective of this study was to investigate the P uptake of rice plants based on the soil P supplying capacity and the fertilizer use efficiency in the typical P-deficient soils of Madagascar. We conducted a nutrient omission trial using 36 top soil samples collected from both upland and lowland rice croplands in the central highlands of Madagascar. Rice (CV. X265) was cultivated under submerged condition for a month using one-liter pots with four treatments: pots with no fertilizer (Ctrl plot), only nitrogen (N) (N plot), only P (P plot), and N and P (NP plot). Total and available P (Olsen P) contents of soils were determined, and the soil P was fractionated following the modified Hedley method. The amount of P uptake and biomass of rice were measured at harvest.

Total P content varied from 200 to 3200 mg P kg－1 soil among the samples. Labile P (Resin-Pi and NaHCO3-Pi) content had a better correlation with P uptake by rice (Fig. 1) than total P. The biomass production of rice was mostly limited by the low P availability and the sole P limiting was frequently observed in the soils with less than

25 mg P kg－1 soil of Olsen P. The less-labile P fraction (NaOH-Pi), which was the most dominant P fraction in most soils, was increased with oxalate-extractable Al and Fe (active Al and Fe). The P use efficiency by rice was significantly decreased with the active Al and Fe in soils (Fig. 2). It is, therefore, suggested that the applied P was bonded to the active Al and Fe and became less readily available. Our results revealed that the most soils in rice croplands in the central highlands of Madagascar are under P deficient status, and labile P fractions are significant for the P uptake by rice although it generally had a small portion of total P (3.5% on average) in most of the soils. The active Al and Fe play a significant role to decrease the use efficiency of applied P. The mobilization of less-labile P associated with active Al and Fe would be an essential practice to break through the P-deficient conditions in rice croplands in central highlands of Madagascar.

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Figure 2. P use efficiency in relation to active

Al and Fe in soils.

Figure 1. P uptake and labile P (Resin-Pi +

NaHCO3-Pi) in the Ctrl plot.

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Olsen-P can predict the plant-availability of phosphorus in recycling fertilizers Eva Brod1, Anne Falk Øgaard1

1NIBIO, Norwegian Institute of Bioeconomy Research, PO Box 115, 1431 Ås, Norway.

Keywords: Recycling, prediction, extraction The P fertilization effect of new recycling fertilizers is commonly unknown. Growth experiments are the most reliable method to determine mineral fertilizer equivalents (MFE) of recycling fertilizers, but are too time-consuming and expensive to be used as a standard procedure. Application of chemical extraction methods to recycling fertilizers is suggested as an operational and straightforward approach for predicting P availability. The objective of this study was to identify the chemical extraction method, which best predicts MFE of recycling fertilizers. To this aim, we compiled the results of three experiments. In experiment 1 (Brod et al. 2015), we studied 9 recycling fertilizers, in which P was mainly present as Ca-phosphates of different solubility. In experiment 2 (Øgaard and Brod 2016) and 3 (Alvarenga et al. 2017), we studied 21 sewage sludges, in which P was mainly bound to Al and/or Fe. The MFE was determined by pot experiments, where ryegrass or barley was grown in a mixture of sand and peat. Various standard soil- and fertilizer extraction methods (n=9) were applied to the recycling fertilizers, and soluble P was determined as fraction (%) of total P. Comparing all extraction methods and including the results from all 3 experiments, MFE was best predicted by the first two steps of the modified Hedley fractionation (water and 0.5 M NaHCO3) (Figure 1). The modified Hedley fractionation may be replaced by the simpler Olsen-P extraction (0.5 M NaHCO3), as there was a good relationship (R2 = 0.79) between the two methods (only conducted in experiment 1 and 2). We recommend declaring the P quality and predicting P plant-availability in recycling fertilizers by 1) their total P concentration, and 2) the Olsen-soluble P fraction.

Figure 1: Relationship between P in recycling fertilizers being extractable during the first two steps of the modified Hedley fractionation and their mineral fertilizer equivalents (MFE) in pot experiments.

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References - Alvarenga E, Øgaard AF, Vråle L (2017) Effect of anaerobic digestion and liming on plant availability of phosphorus in iron- and aluminium-precipitated sewage sludge from primary wastewater treatment plants. Water Science & Technology 75 (7):1743-1752 - Brod E, Øgaard AF, Haraldsen TK, Krogstad T (2015) Waste products as alternative phosphorus fertilisers part II: Predicting P fertilisation effects by chemical extraction. Nutrient Cycling in Agroecosystems 103: 187-199

- Øgaard A, Brod E (2016) Efficient phosphorus cycling in food production: Predicting the phosphorus fertilization effect of sludge from chemical wastewater treatment. Journal of Agricultural and Food Chemistry 64 (24):4821-4829

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Changes of soil phosphorus fractions in larch plantations across the chronosequence in moutainous region of eastern Liaoning Province, China

Fanpeng Zeng1,2, Xin Chen1, Guangyu Chi1 1Key Laboratory of Pollution Ecology and Environmental Engineering, Institute of Applied

Ecology, Chinese Academy of Sciences, Shenyang 110016, China 2University of Chinese Academy of Sciences, Beijing 100049, China

Keywords: Soil P fractions, stand age, larch plantations Soil phosphorus (P) is one of the most important factors that influence the growth and quality of larch plantations. The dynamic changes of soil P forms are usually considered to be the indicator of the ability of soil to supply P. However, the study of soil P fractions across the larch plantation chronosequence is seldom been studied. The aim of this study is to reveal the variations of soil P fractions and assess the soil P availability with the development of larch plantation. In this study, larch plantation including three stand age classes (10, 25 and 50-year-old, respectively) were selected. Soil P fractions concentration in 0-20cm and 20-40cm were determined by modified Hedley soil P fraction method. Our results showed that, the concentration of soil total P significantly decreased at 25 and 50-year-old stand, possibly due to the single species composition and the whole-tree harvesting method in local place. The concentration of soil labile P forms including Resin-P, NaHCO3-Pi in both two soil layers significantly decreased with the stand age, indicating that soil P availability was gradually decreased with the stand age. The concentration of NaOH-Po decreased with stand age, possibly due to the increase of P mineralization. Our results indicated that the soil P supply capacity of larch plantations was gradually decreased with the stand age. And the NaOH-Po could also be released when soil P was in short supply.

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Using a tri-isotope (13C, 15N, 33P) labeling method to quantify rhizodeposition from a tropical legume, Canavalia brasiliensis

Pierre Stevenel1, Emmanuel Frossard, Samuel Abiven, Idupulapati M. Rao, Federica Tamburini and Astrid Oberson

1Institute of Agricultural Sciences, Plant Nutrition Group, ETH Zurich, Eschikon 33, 8315 Lindau, Switzerland

Keywords: Plant labeling, Rhizodeposition, Isotopes Belowground (BG) plant inputs, including roots and rhizodeposition, are a major source of soil organic matter. Knowledge on the amounts and turnover of BG carbon (C), nitrogen (N) and phosphorus (P) in soil is critical to the understanding of how these elements cycle in soil-plant system. However, the assumptions underlying the quantification and tracking of rhizodeposition using isotope labeling methods have hardly been tested. The main objectives of our study were (i) to describe a novel method for the simultaneous investigation of C, N and P rhizodeposition, and (ii) to test the methodological assumptions underlying quantification of rhizodeposition. By using a tri-isotope (13C, 15N, 33P) labeling method, a pot experiment was conducted to compare the isotopic composition of roots and rhizodeposits while a rhizobox experiment allowed determining the 13C, 15N and 33P tracer distributions within the root system over time and space. Both experiments were conducted in C-free and low N and P sand under greenhouse conditions. The combination of the 13CO2 single-pulse labeling with the simultaneous 15N and 33P cotton-wick stem feeding effectively labeled Canavalia brasiliensis roots and facilitated the estimation of rhizodeposited C, N and P input from root systems. However, the isotope distribution was uneven within the root system for all three elements. Additionally, we observed a progressive translocation from shoot to roots for 15N and 33P over 15 days after labeling while the 13C tracer was diluted with newly assimilated non-enriched C compounds over time. Younger root sections also showed higher specific activities (33P/31P) than the older ones. The high 33P radioactivity recovered in sand right away at the first sampling was attributed to an artefact generated by the stem feeding labeling method, representing 0.1% of the fed 33P. Overall, our results suggest that the assumptions underlying the use of isotope methods for studying rhizodeposition are violated, which will affect the extent of quantification of rhizodeposition. The consequences of non-homogenous labeling of root segments of different age require further investigation. The use of a time integrated isotopic composition of the root is recommended to not only account for temporal variation of isotopes but also to improve the method of quantifying plant rhizodeposition.

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Quadrupole Mass Spectrometer Method for the Quantification of Inorganic and Organic Phosphate Species for Applications in 18O- Stable Isotope Probing

Aimée Schryer1, Steven D. Siciliano1, Kris Bradshaw2 1Department of Soil Science, University of Saskatchewan, 51 Campus Drive, Saskatoon,

Saskatchewan, Canada 2Federated Cooperatives Ltd., 401 22nd Street East, Saskatoon, Saskatchewan, Canada

Keywords: Mass spectrometry, stable isotope probing

When Phosphorus (P) fertilizers are added to soils, both the identity of the microorganisms incorporating the P or into which biological macromolecules is not known. By using heavy phosphate (P18O(n)) stable isotope probing, one can track the P as it cycles through the soil and microbial populations. However, methods to identify P18O(n) incorporation into microbial macromolecules and the optimal times to incubate samples to track P18O(n) incorporation into DNA are not established. Soil (10g) microcosms were treated with either: (i) 18O-labelled phosphate, (ii) unlabelled phosphate or (iii) Milli-Q control, dissolved in a biostimulatory solution consisting of 0.24 mM HNO3 [3.4 mg/L N], 0.24 mM Fe(III)NH4-citrate [13 mg/L Fe(III)], 22 mM SO4 [700 mg/L S]) and 0.1 mM P-species (3.1 mg/L P) at a circumneutral pH. Microcosms were sampled for both total P via sequential extraction and DNA. Double stranded DNA samples are digested to their respective 3’-deoxynucleoside 5’-monophosphates (dNMP). The collision-induced dissociation (CID) tandem mass spectrometric (MS/MS) analysis of each P-species was conducted using a QTRAP® 4000 LC/MS/MS system attached to an Agilent 1200 Series HPLC System. The MS/MS, a hybrid triple quadrupole–linear ion trap mass spectrometer (QqQ-LIT), is equipped with a 'Turbo V Ion Spray' ESI source where nitrogen was utilized as the collision gas. Phosphorus extracted from resin anion exchange strips was measured on the MS/MS and compared with the SEAL AutoAnalyzer 3 HR (AA3) to determine if results are comparable (Fig 1 and 2). Results show that isotopic composition does not have a significant effect upon the microbial uptake of the orthophosphate or precipitation reactions with soil. A mass balance equation will determine total P within the microcosms. Overall, using the MS/MS method in SIP experiments will allow anthropogenic P to be followed within ecosystems to better understand soil activity.

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Figure 1 and 2: Resin extractable 16O- and 18O- orthophosphate by week. Control microcosms had low 16O-orthophosphate concentrations whereas no 18O-orthophosphate was measured outside of labelled microcosms.

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Single-cell approach to probing phosphate solubilizing bacteria in by Raman spectroscopy with D2O labelling

Hong-Zhe Li1, Li Cui1, Kai Yang1, Yong-Guan Zhu1 1Key Lab of Urban Environment and Health, Institute of Urban Environment, Chinese Academy

of Sciences, Xiamen 361021, China.

Keywords: Single-cell Raman, PSB, D2O- SIP Phosphorus (P) is an essential nutrient for plant growth, phosphate solubilization bacteria play a key role in soil phosphorus cycling, but remain largely unknown because most of bacteria are uncultured. Hence, it is essential to develop a new method to discern the culture independent phosphate solubilization bacteria at the single-cell level. In this study, we present a culture independent single cell method by combining Raman spectroscopy with D2O-stable isotope probing. The C-D shift is a distinguishable biomarker for active bacteria. By applying this biomarker into the Raman imaging in both artificial media and soil, our results hold promise for Raman based discerning of phosphate solubilization bacteria at single-cell level. This single cell approach will allow us to discern phosphate solubilization bacteria in different habitats and excavate the uncultured microbial resources.

Figure 1: Photomicrograph and Raman images of soil communities incubated in the dissoluble-P free soil for 24h. The yellow regions were identified as bacteria (a), the red regions were identified as PSB (b), the purple circles were identified as PSB (c), and the red circles were identified as non-phosphate releasing bacteria and the green circles were identified as non-living things.

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Global variability of soil phosphorus δ18Op values in grasslands Verena Pfahler1, Andrew C. Smith2, Martin S. A. Blackwell1, Steve J. Granger1

1Sustainable Agriculture Sciences – North Wyke, Rothamsted Research, North Wyke, Okehampton, EX20 2SB, UK

2NERC Isotope Geosciences Facility, British Geological Survey, Nicker Hill, Keyworth, Nottingham, NG12 5CG, UK

Keywords: Grasslands, oxygen isotopes, sequential extraction The isotopic composition of oxygen (O) associated with phosphorus (P), (δ18OP) has the potential for investigating P cycling in the soil/plant system because P is mostly associated with O in the environment. This method has been successfully used in soil studies, but data on the range of soil P δ18OP values are limited, especially when it comes to testing the effect of environmental factors like climate. Oxygen from water is the main source for O in P compounds and biological activity is the main driver behind the O exchange between water and P compounds. Both factors, water and biological activity, are highly dependent on climate. The main objective of this study, was to assess the global variability of soil P δ18OP values across different climates and understand what they tell us about P cycling under different conditions, e.g. different soil P concentrations. We focussed on the upper 10cm soil layer of grasslands (natural and managed; Figure 1) and three soil P pools (resin, microbial, and mineral P), which were extracted sequentially. We then purified the extracts using a multistep protocol, with precipitated silver phosphate as the final analyte and analysed the silver phosphate for its δ18OP. There were large variations in the soil P concentrations across the study sites. Resin P ranged between 0.04 and 56 mg P kg-

1 soil, whereas microbial P ranged between 0.2 and 17.5 mg P kg-1 soil. The range of δ18OP values was also large with values of 9.6 to 27 ‰ for resin P, and 9.7 to 21 ‰ for microbial P. The δ18OP values of resin and microbial P were not always similar to each other which implies that either P was not always first cycled through microbes before being released into the resin P pool or that under certain conditions other processes overprint the δ18OP signature of P cycled through microbes. There are several prerequisites for using the δ18OP to study soil P cycling, such as a need for distinct δ18OP values between the various soil P pools. This study revealed the conditions under which the δ18OP of different soil P pools can be used to get a deeper insight into soil P cycling.

Figure 1: Distribution of the grassland sites sampled so far (indicated with blue markings).

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Vertical distribution and accumulation of phosphorous in uncultivated and cultivated Andisols of Hokkaido, Japan

Masayuki Tani, Rintaro Kinoshita Research Center for Global Agromedicine, Obihiro University of Agriculture and Veterinary

Medicine, Obihiro, Hokkaido 080-8555, Japan.

Keywords: Andisols, phosphorous, accumulation Heavy application of phosphate fertilizers and subsequent accumulation of phosphorous in arable soils, especially in Andisols, are critical issues for sustainable agriculture in Japan. We investigated the effects of fertilization and plant nutrient management on phosphorous accumulation and its speciation in uncultivated soils (virgin soils) and cultivated soils (arable soils) of Tokachi district, Hokkaido, Japan. Two pairs of virgin and arable soil profiles were selected to evaluate the vertical distribution of total, sequentially extractable and available phosphorous in the soils. Bulk and undisturbed soil samples were collected every 5 cm depth increment up to 1 m depth at each soil profile. Net accumulated amounts of phosphorous in the arable soils were calculated in consideration of bulk density and the difference in thickness of soil layers between arable and adjacent virgin soils mainly due to soil compaction and soil carbon loss. Surplus phosphorous was accumulated in the plow layer at the depth of 0-40 and 0-30 cm of the arable soil profiles, which were classified as Low-humic volcanic ash soils (Typic Hapludands) and Cumulic volcanic ash soils (Pachic Melanudands), respectively. The phosphorous was distributed homogeneously in the plow layer due to physical disturbance and mixing. The vertical distribution of phosphorous in the virgin and arable soils indicated that most of the surplus phosphorous accumulated without leaching in the plow layer of the Andisols (Figure 1). Net accumulated amounts of phosphorous in the cultivated Andisols were remarkably large, of which estimated annual accumulation rates were more than 56.7 kg-P ha-1. Total accumulated amounts of total P were 3.6 and 4.6 Mg ha-1 in Low-humic volcanic ash soils and Cumulic volcanic ash soils, respectively. Most of the accumulated phosphorous might be specifically adsorbed by active aluminum and iron, which could be extracted by fluoride through strong ligand-exchange reaction. Amounts of available phosphate by Truog method accounted for 3 to 5 % of soil total P. Vertical distribution of total phosphorous in the soils was closely related with cadmium only.

Figure 1: Soil profiles and vertical distribution of soil total P of virgin and arable soils (a) Low-humic volcanic ash soils (Typic Hapludands) and (b) Cumulic volcanic ash soils (Pachic Melanudands).

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Soil phosphorus testing for intensive vegetable cropping Stany Vandermoere1, Stefaan De Neve1

1Department of Environment, Faculty of Bio-Science Engineering, Ghent University, Coupure Links 653, 9000 Ghent, Belgium.

Keywords: Fertilization, Phosphorus, Vegetables Recently there is a renewed interest in improving soil P tests for more efficient P fertilization. This is driven by environmental concerns and rapidly decreasing P resources. Currently there is a variety of such soil tests that differ mainly in how the plant available P pool is determined, and that were developed mainly for major arable crops. These tests have been much less validated for vegetable crops, with often a very short growing season and limited rooting system. Hence, these crops are more sensitive to P shortages. Field trials have shown that the currently used soil P test fails to predict the P fertilizer requirement for vegetable crops. Also, new insights were gained in recent years on how the plant available P pool can be determined. With this in mind, we set up a study to answer following questions: (i) which soil P test predicts the plant available P for intensive vegetable crops the best and (ii) can new insights such as combining different soil P tests improve fertilizer recommendations for intensive vegetable crops? To this end bulk samples of 41 soils with very different P status (based on ammonium lactate extractable P) were collected. The plant available P pool of these soils was determined using 6 commonly used soil P tests (P-CaCl2, P-water, P-Olsen, P-acetate, P-lactate and P-oxalate) and a P fertilizer pot experiment with endive (a very P sensitive vegetable crop) was conducted. Six pots of each soil were planted with endive. Three of these pots received no P fertilization (0P) and three pots received ammonium polyphosphate equivalent to 24 kg P ha-1 (24P). All other factors were kept constant. Relative crop yield of the 0P fertilized plants compared to the 24P fertilized plants was determined. Plotting the relative yield against P status of the soil per soil P test allowed to fit a Mitscherlich curve through the data. Also the combination of two different soil P test to predict the relative yield with a Mitscherlich equation was evaluated. R² values of the Mitscherlich equations revealed that P-water and P-acetate predicted the relative yield of the 0P plants the best and that combining two different soil P test gave no extra predictive power. Further statistical analyses based on critical P values per soil P test, the uncertainty of the critical P values and the capacity of soil P tests to differentiate between soils with and without a P fertilizer effect needs to be done. Results of the analyses will be shown at the conference.

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Can the C and P signature of organic amendments be used to determine soil P availability?

Md Shahinur Rahman1; Cassandra Schefe2; Jizheng He1; Anthony Weatherley1

1 School of Agriculture and Food, The University of Melbourne, Victoria, 3010, Australia 2Soil Science Consultant, Schefe Consulting.

Keywords: Organic amendments, Carbon compounds, Organic Phosphorus, P availability. Organic amendments (OA) can increase phosphorus (P) availability of soil both through the forms of P applied and, the reaction of intrinsic carbon (C) compounds with the soil. The mechanisms for these interactions are likely to be: differential mineralization rates of organic P forms in the OA and; microbial population, soil chemistry, reaction, sorption and solubility of P. Information about the forms and abundance of C and P compounds in OA (their signature) may allow us to predict the suitability of an OA to increase P availability. The aim of this study was to identify, the forms and abundance of C and P compound from a sequence of soil amendments: food waste, food waste compost, food waste biochar; biosolids, biosolids compost, biosolids biochar using 13C NMR and 31P NMR, respectively. Gas chromatography-Mass spectroscopy (GC-MS) were used to identify different forms of C compounds. A synchrotron (XANES) study will be performed to identify P speciation from OA applied to an acid soil.

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Preliminary characterization of phosphorus fractions in soils of two catchments under distinct anthropogenic pressures

Bernardete Vieira1, Anabela Reis2, Marta Roboredo3 1PhD student of School of Agrarian and Veterinary Sciences, University of Trás-os-Montes e Alto

Douro (UTAD), Quinta dos Prados, 5001-801, Vila Real, Portugal 2Department of Geology, University of Trás-os-Montes e Alto Douro (UTAD), Vila Real, Portugal

3Department of Biology and Environment, Chemistry Center, University of Trás-os-Montes e Alto Douro (UTAD), Vila Real, Portugal

Keywords: Soil P, land use, catchment features Phosphorus (P) is an essential element for plant growth, with reduced solubility and availability in soils, and is frequently used in fertilisations to ensure agricultural productions. However, long-term P applications may result in excessive soil P, contributing to its enrichment in watercourses. Mobility and availability of P in soils depends on which forms are present. In this study, soil P from two small catchments in the north of Portugal exhibiting poor water quality – Vilariça, an intensive irrigated agricultural area, and Vizela, where livestock productions (dairy farming) complement the textile industry - was characterized. Soils derive from different parent material and are subject to different agricultural systems and climatic conditions. Twelve surface soil samples for each catchment, covering the most significant land uses, were collected and analysed for pHH2O, total C and N, sand, silt and clay, and cation exchange capacity. Soil P was characterized: water extraction (WEP), total (Pt) and inorganic P (Pi) by the ignition method and organic P (Po) = Pt – Pi, and the inorganic P fractionation based on the Chang and Jackson proposal (C&J) - easily soluble P, Al-P, Fe-P, redundant P, Ca-P and residual P. Soils from the Vizela catchment present higher Pt contents, up to 2300 mg P kg-1, while in Vilariça Pt reaches 1500 mg P kg-1. In both catchments, Pi>Po for most soils, but Vizela soils present higher Po content (up to 632 mg P kg-1). WEP, a parameter frequently correlated with P in runoff waters, achieves values greater than 17 mg P kg-1 for both catchments suggesting potential P losses to waters. The sum of Pi fractions of the C&J method is higher in Vizela, where soil P is present mostly in the Al-P form (44 -1179 mg P kg-1), whereas for Vilariça soil P is mostly linked to Ca (9 - 698 mg P kg-1). The easily soluble C&J fraction presents significant correlations with WEP (R2=0.93** and 0.83**, Vilariça and Vizela, respectively). The results obtained in the two catchments reflect the different agricultural systems present, namely the dairy farming systems with frequent use of animal manures as a source of nutrients to crops in the Vizela catchment, and the intensive horticultural and fruit productions with high inputs of chemical fertilizers in the Vilariça catchment. Further investigation is required for a complete characterization of soil P and for a better understanding of the P mobility from soils to the environment within the studied areas.

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Distribution of fertilizer phosphate in a coarse sandy soil profile after different long-term liming strategies

Musibau O. Azeez1, Julie T. Christensen1, Sabine Ravnskov2, Goswin J. Heckrath1, Rodrigo Labouriau3, Bent T. Christensen1 & Gitte H. Rubæk1.

1Department of Agroecology, Aarhus University, Blichers Allé 20, 8830 Tjele, Denmark 2Department of Agroecology, Aarhus University, Forsøgsvej 1 DK-4200 Slagelse, Denmark

3Department of Mathematics, Aarhus University, Ny Munkegade 118, 8000 Århus C, Denmark

Keywords: Liming, soil pH, P sorption properties

We studied the distribution of P in the profile of an arable coarse sandy soil at Jyndevad Experimental Station, Denmark, using plots treated with mineral fertilizer P and different rates of lime. Since 1942, lime has been added at three rates while P has been added at an annual rate of 15.6 kg P/ha since 1944. Reference treatments were no lime and no P additions since 1942/44. Soil cores (0-100 cm) were retrieved in autumn 2016 shortly after barley harvest. We hypothesized that long-term liming, and the resulting differences in soil solution pH and cation composition, affects P mobility and sorption properties in the soil profile, and that long-term liming and annual P addition increases soil C content in response to improved crop growth. Soil chemical properties (pH, total P, total inorganic (Pi) and organic P (Po), Olsen P, water extractable P (Pw), soil C, and oxalate-extractable P, Fe and Al) were determined in five depths. The P sorption index (PSI), based on addition of 50-mmol P kg-1 soil, and was used to evaluate soil sorption capacity. Soil pH significantly increased with increased liming addition to at least 70 cm depth. For P fertilized soil, total P, Pi, Olsen P, Pw and oxalate P were significantly higher in 0-30 cm than in soil depth below, indicating that P had not migrated down the soil profile. Liming significantly increased soil C in 0-30 cm. There were strong relations between oxalate-extractable Al and PSI, while the relations between oxalate-extractable Fe and PSI were weak. In conclusion, long-term mineral fertilizer P application only affected the distribution of P to 30 cm depth. P sorption capacity increased substantially with depth until 50 cm, and it was only moderately affected by liming and P additions until 30 cm depth. Furthermore, P sorption capacity was related to the presence of amorphous Al oxides, while the role of amorphous Fe oxides was inferior.

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Factors controlling the rate of depletion of phosphorus in soils of contrasting chemistry

Jane Hawkins1, Martin Blackwell1, Tegan Darch1, Steve Granger1, Sarah Dunham2, Javier Hernandez2, Steve McGrath2

1Sustainable Agriculture Sciences – North Wyke, Rothamsted Research, North Wyke, Okehampton, EX20 2SB, UK

2Rothamsted Research, Harpenden, Hertfordshire, AL5 2JQ, UK

Keywords: Soil chemistry, fertiliser, depletion Phosphorus (P) availability to crops is dependent on the equilibrium between the concentration of phosphate ions in the soil solution, and the ability of the soil to adequately replenish this supply as it becomes depleted around the root zone (buffering capacity). Various soil properties including pH, iron (Fe) and aluminium (Al) oxide content and organic carbon are a major influence on the biological and chemical processes that regulate both the rate of release and availability of P. Application rates of fertilizer P are designed to maintain soil P above a critical threshold necessary to achieve optimal yield for any given crop, but do not consider soil type and properties. We carried out a pot experiment to determine how different potential P-binding parameters of 22 contrasting soils affect P depletion rates over time (Fig 1).

All soils had an initial Olsen P concentration of 16-25 mg litre-1. Ryegrass (L. perenne, var. Abermagic), sown at a rate of 0.5 g pot-1 was grown in 1 kg of a 50:50 mix of soil:quartz chips to ameliorate any structural limitations in a controlled environment. Plants were grown for up to 448 days and harvested every 3-4 weeks (18 harvests in total). Daily P uptake rate was calculated for each soil for each harvest, with all data

explained by fitting an exponential curve. The coefficients of the fit to the exponential curves (r) were considered to represent the rates of P uptake, and thus the rates of P availability. Multiple regression of r against the soil characteristics showed that the strongest relationship was a negative one with the dithionite extractable oxide content (Fe + Al + Mn), and especially Fe. Grass yields between the different soils were variable and P availability was dependent on soil properties controlling its rate of release. These results, in combination with better critical P data for different soils, will enable the development of soil-specific P fertiliser application rates and frequency recommendations.

Figure 1: 22 different soils with varying properties were used in the soil P depletion study.

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Effects of a short-term fertilization on biological phosphorus cycling in temperate forest soils captured by oxygen isotopic composition in phosphate

Maja Siegenthaler1, Emmanuel Frossard1, Éva Mészáros1, Chiara Pistocchi2, Federica Tamburini1

1Group of Plant Nutrition, Institute of Agricultural Sciences, Department of Environmental Systems Science, ETH Zurich, Eschikon 33, 8315 Lindau, Switzerland

2Eco&Sols, Montpellier SupAgro, Univ Montpellier, CIRAD, INRA, IRD, 34060 Montpellier, France

Keywords: Short-term fertilization trial, phosphorus pools, oxygen isotopic composition

Forest trees, as most plants in terrestrial ecosystems, take up their phosphorus (P) mainly as inorganic phosphorus from the soil solution, which is supplied with P from other less available pools by abiotic and biotic processes. The quantification of P pools by well-established chemical extractions gives a picture of their relative proportion but does not capture the processes underlying P cycling. The isotopic composition of oxygen (O) bound to P in phosphate can be used as an indicator for biological activity as the exchange of O between water and phosphate at typical Earth surface temperatures is only promoted by biological activity. Our study is part of the German priority program "SPP 1685 - Ecosystem Nutrition". In this framework a two-year long fertilization experiment was set up at two contrasting beech forest field sites in Germany: a site with a soil containing high amount of available P and another with a soil presenting little available P.

Figure 1: Phosphorus fluxes (continuous lines) and interactions (dotted lines, + for positive and - for negative feedback) in the organic horizon of forest soils studied in the project.

The overall objective of the program was to investigate the importance of soil organic matter turnover on P cycling under environmental changes induced by

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fertilization (Figure 1). We hypothesize that changes in available nutrients in soil will impact microbial activity with cascading effects on the P cycle. The effects of nitrogen (N) and P inputs, added in water-soluble form alone or combined in a full factorial design, were studied at these two sites. In addition, several days before sampling the organic horizon of the two sites was labelled with 18O enriched water. We performed Hedley extractions plus measured 18O in the resin and microbial P pools. We observed higher P concentrations and higher 18O label incorporation in the resin pool of the P and combined NP than for N and control treatments in the soil with high amount of available P, but not in the soil with less available P. No fertilization effects were observed for the microbial P pool at either site.

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Quantitative measures of myo-IHP in NMR spectra of soil extracts using spectral deconvolution fitting that includes an underlying broad

signal

Jolanda E. Reusser1, René Verel2, Emmanuel Frossard1, Timothy I. McLaren1 1Group of Plant Nutrition, ETH Zurich, Eschikon 33, 8315 Lindau, Switzerland.

2Laboratory for Inorganic Chemistry, ETH Zurich, Vladimir-Prelog-Weg, 8093 Zurich, Switzerland.

Keywords: inositol phosphates, NMR, deconvolution myo-Inositol hexakisphosphate (myo-IHP) is an important form of organic P found in soils. It is typically measured in soil extracts using solution 31P nuclear magnetic resonance (NMR) spectroscopy followed by spectral deconvolution fitting of the phosphomonoester region. Two different approaches for the deconvolution fitting procedure have been reported (Turner et al., 2003 and Bünemann et al., 2008) (Figure 1). The main difference being the inclusion of an underlying broad (background) signal in one of the methods. The aim of this study was to assess these two methods in regards to their quantification of myo-IHP in alkaline soil extracts. Six diverse soils (depth 0-20 cm) with varying concentrations of organic P (112 – 1505 mg P/kg) were extracted with NaOH-EDTA and analysed with 31P NMR spectroscopy before and after the addition of a myo-IHP spike. The phosphomonoester region of all spectra were processed using the two aforementioned deconvolution approaches. Recoveries of added myo-IHP were on average 94% (standard deviation: 6) across all soils with the inclusion of an underlying broad signal (Bünemann et al. 2008). In contrast, recoveries were on average 122% (standard deviation: 32) when fitting the peaks to the baseline (Turner et al. 2003). Overestimation of myo-IHP using the latter method also varied for the individual peaks, which was on average 8% higher for the C1/C3 peak compared to the C2 peak. An important difference between these two peak positions is the intensity of the broad peak (Figure 1). We recommend that an underlying broad signal be included when carrying out spectral deconvolution of the phosphomonoester region for the quantification of myo-IHP in soil extracts. References - Bünemann EK, Smernik RJ, Doolette AL, Marschner P, Stonor R, Wakelin SA, McNeill AM (2008) Forms of phosphorus in bacteria and fungi isolated from two Australian soils. Soil Biology and Biochemistry 40: 1908-1915. - Turner BL, Mahieu N, Condron LM (2003) The phosphorus composition of temperate pasture soils determined by NaOH–EDTA extraction and solution 31P NMR spectroscopy. Organic Geochemistry 34: 1199-1210.

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Average recovery

added myo-IHP:

94%

Average recovery

added myo-IHP:

122%

C2

C1,3

C1,3

Figure 1: Example of 31P NMR spectra on NaOH-

EDTA soil extracts with the deconvolution

approach of Turner et al. 2003 (above) and

Bünemann et al. 2008 (below). The broad peak

(purple) and the myo-IHP peaks (red) have been

identified.

C2

C4,6

C4,6

C5

C5

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Prediction of yield response to phosphorus fertilizer using six different soil phosphorus tests

Julie T. Christensen1, I. F. Pedersen1, C. Lemming, S. Husted, Gitte H. Rubæk1 1Department of Agroecology, Aarhus University, Blichers Alle 20, 8820 Tjele, Denmark

Keywords: Soil phosphorus tests, fertilization requirements

Farmers rely on soil phosphorus (P) tests to estimate P fertilization requirements. In

Denmark, the Olsen P method is used for this, but it has been found, that it does not

always identify soils where P fertilization is required. The opposite situation may also

occur, where a soil P test erroneously indicate the requirement for additional P

fertilization. Therefore, to ensure sustainable use of P fertilizers, more reliable soil P

test methods are needed. Recent studies have demonstrated that the Diffusive

Gradients in Thin Films method (DGT) in many cases is superior to classical soil P tests

(e.g. Mundus et al. 2017, Speirs et al. 2013 & Mason et al. 2010). In this study, we

compared the DGT method to the Olsen P method based on how well they predicted

grain yield response to P fertilization in 35 field trials carried out in Denmark in 2013,

2014, 2016 and 2017 with spring barley as the test crop. Each field trial had a

randomized block design with four replications of two treatments. One treatment

received 30 kg P/ha applied as triple superphosphate, and the other treatment did

not receive any P. Other nutrients were added according to need in both treatments.

Soil was sampled for soil P tests before sowing. Only eight out of 35 trials had a

significant positive yield response to P application, whereas the remaining trials did

not respond to P fertilization. This confirms that Danish agricultural soils generally

are rich in P, and that the soil P pool in most cases were able to supply spring barley

with sufficient amounts of P. Based on critical limits for Olsen P and DGT derived

from literature, we found that the DGT method was superior to Olsen P method in

predicting where yield response to P fertilization would occur (six out of eight field

trials) whereas Olsen P method only predicted two out of the eight field trials

correctly. The Olsen P method correctly predicted no yield response in 25 out of 28

trials, whereas the DGT method only did so in 17 out of 28 trials. For the conference,

the dataset will be expanded with results from four additional soil P test methods

and with five field experiments carried out in Sweden and Finland.

References - Mason, E., Mcneill, A., Mclaughlin, M. J. & Zhang, H (2010) Prediction of wheat response to an application of phosphorus under field conditions using diffusive gradients in thin-films (DGT) and extraction methods. Plant and Soil 337:243-258. - Mundus S, Carstensen A, Husted S (2017) Predicting phosphorus availability to spring barley (Hordeum vulgare) in agricultural soils of Scandinavia. Field Crops Research 212: 1-10.

- Speirs, S. D., Scott, B. J., Moody, P. W. & Mason, S. D (2013) Soil phosphorus tests II: A comparison of soil test-crop response relationships for different soil tests and wheat. Crop & Pasture Science 64:469-479.

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Impact of crop diversification on soil organic matter pools and phosphorus dynamics

Gina Garland1, Anna Edlinger1, Justine Boitel1, Chantal Herzog1, Marcel van der Heijden1

1Plant-Soil Interactions, Agroscope, 8046 Zurich, Switzerland

Keywords: Organic phosphorus, soil organic matter pools Making sound phosphorus (P) fertilizer recommendations for farmers is difficult, since total soil P does not give an indication of plant availability, and P in the soil solution is extremely dynamic. As such, finding alternative soil P diagnostics to help P fertilizer recommendations is needed, as over-applying P is i) expensive, ii) environmentally problematic, and iii) wasteful. One approach to improving P fertilizer recommendations is to take into account organic P pools and turnover times during crop growth. However, measuring rates of organic P mineralization is a difficult task since it requires the use of dangerous and expensive radioisotopes, as well as time-consuming soil incubations. Furthermore, this approach does not give an indication of how this mineralized P is used by plants. It was recently found, however, that the organic P content of the coarse soil organic matter fraction (>53 µm) was significantly correlated with P mineralization rates (Wyngaard et al., 2016). The objective of this study was thus to determine i) if crop biodiversity has an effect on the proportion and type of organic P compounds in the coarse fraction, and ii) if these pools are correlated with crop yields. We hypothesized that cropping systems with a large diversity of crops in rotation would have a higher amount of organic P in the coarse fraction, and that this would be positively correlated with crop yields. In order to test these hypotheses, we collected soils from wheat fields across a North-South gradient in Europe, spanning from Sweden through Spain, as well as from grassland soils as a positive control. These soils were then planted with Plantago lanceolata, and grown for ten weeks in a greenhouse, after which time the total biomass was measured in each pot. In parallel to crop growth, a proportion of the unplanted soils were 8mm sieved, dried, and separated into coarse (>53 µm) and fine (>53 µm) fractions. Next, the total C, N, P and organic P were measured on each fraction, as well as the specific organic P compounds using 31P NMR spectroscopy. Our preliminary results indicate that crop rotations with between three and six crop species in rotation has a significantly higher proportion of organic P to total P in the coarse fraction compared to crop rotations with less than two or more than six. We conclude that using information on the organic P content of soil organic matter pools can significantly improve P fertilizer recommendations for farmers. References - Wyngaard N, Cabrera M, Jarosch K, Buenemann E (2016) Phosphorus in the coarse fraction is related to soil organic phosphorus mineralization measured by isotopic dilution. Soil Biology and Biochemistry 96:107-118.

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Using the stable oxygen isotope composition of phosphate to understand phosphorus spatial variability and cycling in soils

Steven J. Granger1, Verena Pfahler1, Andrew C. Smith2, Martin S. A. Blackwell1 1Sustainable Agriculture Sciences – North Wyke, Rothamsted Research, Okehampton, EX20 2SB,

UK 2NERC Isotope Geosciences Facility, British Geological Survey, Keyworth, Nottingham, NG12

5CG, UK

Keywords: Grasslands, δ18OPO4, sequential extraction Excessive use of phosphorus (P) fertilisers can have detrimental environmental effects, therefore knowledge of how P is cycled in the environment is essential. Phosphorus dynamics in soils is complex, however recent advances in the use of the stable oxygen isotope ratio of phosphate (δ18OPO4) has opened a new set of research possibilities. A recent study looking at the δ18OPO4 of HCl-extractable PO4 (HCl-P) in an undisturbed grassland soil indicated that spatial variation might occur due to agricultural management. Soil δ18OPO4 was significantly linked to soil P concentration, a relationship that was not present in a ploughed soil within the same field. However, two issues confound the initial study: firstly, the number of samples taken from the unploughed part of the field were limited, and secondly, the HCl extraction used was not undertaken as part of a sequential extraction and therefore bulked many extractable forms of P together. The main objectives of this study were to better resolve the δ18OPO4 variability within a single management unit and the relationship between the soil P concentration in different extractable soil P forms and δ18OPO4. A statistically robust, spatial survey was carried out in which the different soil P pools were characterised individually for 50 sample locations within a long term unploughed grassland field on Rothamsted Research’s North Wyke farm, Devon, UK. Sequential extraction was used to determine the δ18OPO4 from i) resin-P, ii) microbial-P, and iii) HCl-P.

Table 1. Preliminary data from the sequentially extracted soil P forms and their concentration range, and the preliminary δ18OPO4 values for these soil P pools

Soil P pool (mg P-1 kg-1) δ18OPO4 (‰)

Min Max Mean Std Dev Min Max

Resin-P 0.18 12.9 2.00 2.01 15.8 22.4

Microbial-P 1.75 472 98.6 86.5 14.1 17.4

NaOH/EDTA-Pi 140 868 275 113 na na

NaOH/EDTA-Porg 273 617 464 101 na na

The concentrations of soil extractable P are variable within this individual field (Table 1). Resin-P comprises the smallest proportion, with microbial-P an order of magnitude higher. Soil NaOH/EDTA extractable Pi and Porg comprise the largest extracted pools at the time of writing and are expected to remain the highest, with HCl-P concentrations typically being low after sequential extraction of this soil type. Preliminary data showed that the δ18OPO4 of resin P varies by almost 7‰ across the field, whereas the δ18OPO4 of microbial P is less variable. Future work will investigate what other processes influence the δ18OPO4 of soil P pools, along with the variability

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of the δ18OPO4 at a field scale. This work provides information on soil variability which will have implications in how δ18OPO4 should be sampled and assessed. This is critical for the wider soil δ18OPO4 research community.

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Phosphorus in biological soil crusts: speciation and ecological importance Peter Leinweber1, Karen Baumann1, Ulf Karsten2

1Soil Science, University of Rostock,Justus-von-Liebig-Weg 6, 18059 Rostock, Germany. 2Institute of Biology, University of Rostock, Albert-Einstein-Strasse 3, 18059 Rostock, Germany.

Keywords: Biological soil crust, Phosphorus, XANES, P-fractionation, Hedley

Biological soil crusts consist of lower organisms like bacteria, fungi, algae and sometimes mosses that colonize sediment and disturbed soils worldwide and glue the mineral particles by extracellular polymers. By contrast to their fundamental role in global carbon assimilation and nitrogen fixation, their well established ecological function in the mobilization and cycling of phosphorus (P) has been much less investigated. We sampled BSCs and the sediment or soil they are covering in various climatic zones for studies of biodiversity and P cycling. Study areas ranged from artic and subarctic (Iceland, Norway), temperate (Germany) (Baumann et al. 2017), mediterranean (Southern Chile) to extreme arid climates (e.g., Atacama desert Chile). We investigated the P compounds in the BSCs and underlying sediment/soil by sequential fractionations and synchrotron-based X-ray absorption near-edge fine structure spectroscopy (XANES), including elemental distributions and spatially-resolved µ-XANES. Irrespectively of the sediment or soil characteristics the sequential P fractionations showed the enrichments in organically bound P forms in BSC´s relative to the underlying mineral matter. BSC organisms acquired Ca-bound P in coastal dune systems and arid climates, and rather Al-/Fe-bound P in temperate and mediterranean forest ecosystems, depending on the major forms of mineral-bound P in the underlying sediment or soil. Surprisingly, elemental mapping and µ-XANES showed that primary inorganic P compounds sometimes were incorporated into the BSCs but in µm-distances from green algae at crust surfaces. Overall, this compilation of data from various studies suggest that biotic (e.g. predominant vegetation, forest use intensity) and abiotic factors (climate, mineral composition of the underlying sediment or soil) shape not only the community structure of phototrophic organisms in BSCs but also the P speciation in various differently available pools. Evidence is provided that BSCs play a fundamental role in the weathering of P containing minerals and transfer of P to biological cycles. References Baumann, K., K. Glaser, J.-E. Mutz, U. Karsten, A. MacLennan, Y. Hu, D. Michalik, J. Kruse, K.-U. Eckhardt, P. Schall, C. Ammer, P. Leinweber. 2017. Biological soil crusts of temperate forests: I. Their role in P cycling. Soil Biology and Biochemistry 109:156-166.

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Availability of polyphosphate versus orthophosphate on alkaline soil to lettuce plants

Qianqian Li1, Ran Erel1 1Gilat Research Center, Agricultural Research Organization, M.P. Negev, 85280. Israel

Keywords: Polyphosphate, Orthophosphate, P availability Polyphosphate (PP) is a condensed chain of orthophosphate (OP), sharing oxygen. Generally, PP fertilizers are thermodynamically unstable and hydrolyze to OP, the available P form for plants. While OP is readily absorbed by soil, PP fertilizer requires initial hydrolysis and thus sometimes is considered “slow release P”. The hydrolysis process has the potential to decrease the dynamic of fixation reaction in soil and hence, to improve P availability. Moreover, PP can function as a chelate for micronutrients and Ca. The aim of this study is to understand the factors governing P availability in OP versus PP fertilizers. Two forms of ammonium-PP (APPw and APPg, produced from white/green phosphoric acid) and two forms of OP (MAP and TSP) were compared to evaluate their availability dynamic. Fertilizers were incubated in alkaline sandy soil for two months. To study plant response to the various P forms, lettuce plant performance was tested in a pot experiment. The temporal dynamic of extractable (Olsen) P was significantly influenced by P form. At the first week, OP fertilizer treated soil had Olsen-P values three times higher than PP and the levels consistently declined for 35 days. For the two PP fertilizers, extractable P sharply increased momentarily after application, followed by moderate increase for ~40 days, reaching values comparable to those of the OP fertilizers. For all P forms, from day 40 to 90, Olsen-P levels changed very little. Lettuce biomass and P uptake were significantly higher for TSP and APPg compared to the APPw. P acquisition was found to be the sole factor determining plant performance. The application of both PP fertilizers resulted in higher Fe, Zn, Ni and Cr concentration in lettuce shoots, confirming the chelating effect of PP. Our results indicate three main characteristics of PP fertilizers: (1) PP availability in soil is gradually increased with time to a plateau while OP availability is highest soon after application following by steady depletion. (2) PP has considerable chelating properties that increases trace-element availability and potentially competes with OP on Ca. (3) PP with different composition significantly differs in its availability to plants. The production process of the two PP fertilizers affects the composition of various P components (i.e., pyrophosphate, triphosphate) which may explain the different availability of APPw vs. APPg to plants.

Figure 1: Lettuce grown in sandy soil with no P fertilizer (control) or 13 mg kg-1 of various P fertilizers

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Plant growth and plant-induced changes in P pools in long-term fertiliser soil amended with straw

Khuyen Thi Kim Hoang1 and Petra Marschner1

1School of Agriculture, Food and Wine, The University of Adelaide, Adelaide SA 5005, Australia

Keywords: Phosphorus, incubation, wheat Phosphorus is an essential nutrient for all living organisms. But P fertiliser resources are finite, therefore P management in cropping systems is important for future food security. The objective of this study was to investigate the effect of long term P fertiliser application on P pools and how they are influenced by straw addition and plant growth. Soils from a long-term P fertiliser trial (9 years) with P rates of 0, 10 and 20 kg ha-1 was used (referred to as 0P, 10P and 20P. To investigate the effect of straw addition on P pools, the soils amended with mature barley straw (5 g kg-1) or left unamended were incubated moist for four months. Then the soils wheat was grown for five weeks. Bioavailable P pools after DeLuca et al. (DeLuca et al. 2015) and available P (resin P) and microbial biomass P (MBP) were determined initially, after 4 months and after wheat growth. After four months, HCl-P and citrate-P were not different from after 10 days but two- fold and three-fold higher in 10P and 20P than 0P, respectively. MBP was two-fold higher than after 10 days; resin P was ten-fold higher in 10P and 20P but below the detection limit in 0P. Compared to unamended soil, straw addition decreased resin P by 50% and increased MBP by 30% but had no effect on HCl and citrate P. After 5 weeks, wheat shoot biomass was similar in all treatments, but shoot P concentration was lower in 0P than 10P and 20 P. MBP with straw was 10-30% lower than after four months, HCl-P was 30% lower. Citrate-P in 0P and 10P was about 30-50% higher than after four months but unchanged in 20P. Addition of barley straw reduced resin P by 50% and HCl-P by 10% in 20P but had little effect on MBP and citrate-P. In conclusion, long term P fertiliser addition increased P pools compared to 0P, but there was little difference between 10P and 20P possibly due to higher P uptake by plants in the field. Wheat straw addition had a greater effect on P pools than the subsequent plant growth. References DeLuca TH, Glanville HC, Harris M, Emmett BA, Pingree MR, de Sosa LL, Cerdá-Moreno C, Jones DL (2015) A novel biologically-based approach to evaluating soil phosphorus availability across complex landscapes. Soil Biology and Biochemistry 88: 110-119.

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Development of an in-field measurement technique for available phosphorus to improve fertiliser recommendations

Susan Tandy1, Roy O'Mahony2, Martin Blackwell1, Jane Hawkins1 1Sustainable Agricultural Sciences, Rothamsted Research, North Wyke, Devon, EX20 2SB, UK,

2CleanGrow UK Ltd, Eden house, Forge Lane, Moorlands Trading Estate, Saltash, Cornwall, PL12 6LX, UK.

Keywords: Fertiliser recommendations, ion-selective electrode, available phosphorus Global agricultural food production relies on phosphorus fertiliser derived from finite rock phosphate deposits. Thus, there is considerable pressure on optimising the use of P fertilisers. At present P fertiliser application rate recommendations are far from efficient, due to two main challenges: i) there is no accurate, reliable, low cost method for measuring plant available P in a range of soils in the field, and ii) a lack of accurate, soil specific fertiliser application recommendations based on such data. Currently the only way to measure soil phosphate in the field is by complex kits involving many solutions and relying on a colour change with the results being crudely determined by eye against a colour chart. The alternative is to send a sample to a soil testing laboratory for analysis, but this is time consuming and expensive, and the soil sampling, sample handling and processing methods can vary, meaning results are often equivocal. Often farmers pool samples to save costs. Waiting days for results to come back means that weather windows may be missed and due to the low number of samples analysed, often one application rate of fertilizer is applied across a whole field which might have widely varying nutrient levels within it. The aim is to develop a rapid field test based on a phosphate ion selective electrode already in use in the hydroponics industry. This would allow farmers and agronomists to divide fields into different sections in order to accurately measure the level of available phosphorus in soil and thus apply fertilizer with higher precision. This would mean that fertilizer costs to farmers could be lowered and fertilizers could be applied at an opportune moment due to the quick analysis time. Pollution and eutrophication of surrounding waterbodies would also be lowered as excess phosphorus would not be applied to fields due to the accurate nutrient measurements. The first stage is to test different soil extractants with the sensor for available phosphorus measurement and compare these to standard laboratory techniques presently used for fertilizer recommendations over a range of soils with different characteristics.

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Phosphorus speciation in forest soil profiles as influenced by soil development Jon Petter Gustafsson, J.R. Marius Tuyishime, Gbotemi Adediran

Department of Soil and Environment, Swedish University of Agricultural Sciences, Box 7014, 750 07 Uppsala, Sweden.

Keywords :Forest soils, XANES spectroscopy, podzolisation Phosphorus (P) is usually not a limiting nutrient for trees, but successive harvests may make P a critical nutrient if the soil P is not replenished. In ongoing work we study the biogeochemical cycling of P in forest ecosystems. Here we present results showing the P speciation of five selected forest soil profiles, of which four were podzolised. For this, we applied P K-edge XANES spectroscopy using the protocol of Eriksson et al. (2016).

Figure 1: Phosphorus K-edge XANES speciation of the Flakaliden Podzol. The width of the horizontal bars is proportional to the white-line intensity, which is related to acid-digestible P (Eriksson et al. 2016).

As an example of the results obtained, Fig. 1 summarizes the results from the Tönnersjöheden Podzol from SW Sweden. Podzolisation processes were clearly reflected in the P speciation, with organic P dominating in the mor layer (Oe horizon), with a low P concentration in the E horizon, and with significant P accumulation in the Bs horizon, most of which was usually bound to Al and Fe (hydr)oxides including allophane. Although Ca phosphate (usually apatite, which was likely inherited from the parent material) was an important P phase in the C horizon, some soils such as Flakaliden contained appreciable amounts of Al- and Fe-bound P also at 1 m depth.

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The results show a clear redistribution of P species as a consequence of 8,000 years of weathering, plant uptake, decomposition and adsorption. The measured speciation illustrates the important roles of organic P and of adsorbed phosphate as dynamic sinks and sources of P. Although present, Ca phosphate is probably of lesser importance at least for short-term P cycling. Reference Eriksson AK, Hesterberg D, Klysubun W, Gustafsson JP (2016) Phosphorus dynamics in Swedish agricultural soils as influenced by fertilization and mineralogical properties: insights gained from batch experiments and XANES spectroscopy. Science of the Total Environment 566-567:1410-1419.

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High nitrogen application favored organic phosphorus accumulation in P-rich calcareous soil

Shuo Chen, Zhengjuan Yan, Shuai Zhang, Bingqian Fan, Qing Chen College of Resources and Environmental Sciences, China Agricultural University, No. 2

Yuanmingyuan Xilu, Haidian, Beijing 100193, P. R. China.

Keywords: Nitrogen, organic phosphorus, microbial community structure High nitrogen (N) fertilizers applied in the intensive agricultural field commonly stimulated soil carbon (C) and N turnover and soil acidification (Han et al., 2015; Treseder, 2008; DeForest et al., 2004). Whereas their influences on the transformation of soil organic phosphorus (Po) were unknown, which is fundamental to understanding the availability and movement of soil Po. In this study, the N fertilizer (i.e., urea) application at the rates of 876 (N1) and 1688 (N2) kg N ha-1 a-1, to influence Po transformation in a calcareous soil were investigated in a 13-year field trial. High rate of urea (N2) significantly increased soil total Po content and proportion. Urea application significantly increased the proportions of NaOH-Po (i.e., Fe- and Al-associated P) by 146-154% determined with chemical fractionation and the proportion of orthophosphate diesters by 22.3-29.0% in Pt determined with 31P NMR. Meanwhile, high rate of urea (N2) significantly increased the proportions of phosphonates and pyrophosphate while decreased orthophosphate proportion in Pt. Soil pH, CaCO₃, the sum of Mehlich-3 extractable Ca and Mg, microbial biomass C (MBC), and alkaline phosphatase (ALP) activity had significant effects on the compositions of soil P (ADONIS, P<0.05). High rate of urea (N2) application significantly decreased pH, CaCO₃, Mehlich-3 extractable Mg and ALP activity, increased MBC and relative abundance of dominant phylum, Proteobacteria, in both of total bacterial and phoD-harboring bacterial communities. These showed that urea application affected both abiotic and biotic processes of Po transformation. Soil acidification induced by urea application results in the increase of Po bounded by Al and Fe hydroxides/oxides (i.e., NaOH-Po). Both the increase in P immobilization and decrease in P biochemical mineralization contributed to the Po accumulation under high N input. Soil pH was the main factor that explained 79.4% and 34.2% of the total bacterial and phoD-harboring bacterial communities in phylum level, respectively. Soil pH and CaCO₃ contents could explain 50.3% and 23.9% of the total variances observed in the compositions of P forms. Therefore, high urea application largely affected soil Po forms through changing soil pH, which consequently influenced on soil Po transformation with both abiotic and biotic processes in P-rich calcareous soil. References - DeForest JL, Zak DR, Pregitzer KS, Burton AJ (2004) Atmospheric nitrate deposition, microbial community composition, and enzyme activity in northern hardwood forests. Soil Sci. Soc. Am. J. 68:132–138. - Han J, Shi J, Zeng L, Xu J, Wu L (2015) Effects of nitrogen fertilization on the acidity and salinity of greenhouse soils. Environ Sci Pollut Res 22:2976–2986. - Treseder KK (2008) Nitrogen additions and microbial biomass: a meta-analysis of ecosystem studies. Ecology Letters 11: 1111–1120.

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Changes in phosphorus availability in soils of an unmanaged mountain spruce forest after bark beetle-induced tree dieback

Jiří Kaňa1,2, Jiří Kopáček1 1 Biology Centre CAS, Institute of Hydrobiology, České Budějovice, Czech Republic.

2 Department of Ecosystem Biology, Faculty of Science, University of South Bohemia in České Budějovice, Czech Republic.

Keywords: Water extractable soil P, forest dieback, litter decomposition Bark beetle infestation caused widespread dieback of the Norway spruce trees in an unmanaged mountain forest in the catchment of Plešné Lake (PL; National park Bohemian Forest, Czech Republic). All dead biomass remained on the forest floor. We observed significant changes in concentrations of mobile phosphorus (P) forms (water-extractable total and reactive P; TPH2O and SRP, respectively) in the upper soil layer (O and A horizons). Soils were sampled in 6-week interval during 10 years following the dieback in 2007 at research plot situated in the PL catchment, and also at a control plot in catchment of Čertovo Lake (CT; the same mountain area, similar altitude, vegetation, and soils). Annual median values of TPH2O sharply increased after the tree dieback from 0.07–0.08 mmol kg-1 (both horizons) in 2008 to 1.0 and 0.76 mmol kg-1 in O and A horizon, respectively, in 2010. Then, the TPH2O concentrations gradually decreased back to their backround from 2008. Similar pattern also occurred for SRP concentrations (Fig. 1) that represented 40–80% of TPH2O. In contrast, annual median values of TPH2O, and SRP fluctuated between 0.05–0.12, and 0.01–0.05 mmol kg-1, without any clear trend at the CT control plot. Elevated P concentrations were also observed in streams draining the PL catchment, and led to increase in primary production in the lake (Kopáček et al., 2017).

Figure 1: Annual median (n=9) concentrations of SRP in water extracts from O and A soil horizons at the Plešné (PL; disturbed) and Čertovo (CT; control) plots.

References - Kopáček J, Fluksová H, Hejzlar J, Kaňa J, Porcal P, Turek J (2017) Changes in surface water chemistry caused by natural forest dieback in an unmanaged mountain catchment. Science of the Total Environment 584–585:971–981.

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Mechanisms controlling P retention during Fe(II) oxidative coprecipitation

Veronica Santoro1, Cristina Lerda1, Per Persson2, Maria Martin1, Daniel Said-Pullicino1, Giuliana Magnacca3, Luisella Celi1

1Università di Torino, DISAFA, Soil Chemistry, via L. da Vinci 44, Grugliasco (TO), 10095 Italy

2Umeå University, Department of Inorganic Chemistry, Umeå, SE-901 87 Sweden 3Università di Torino, Department of Chemistry, via P. Giuria 7, Torino (TO), 10125 Italy

Keywords: Retention, adsorption, coprecipitation.

The sorption of phosphorus (P) on soil minerals is known to strongly influence P cycling and control its retention and bioavailability. Considering the high affinity of Fe (oxy)hydroxides for P, the cycling of these two elements is often closely coupled, particularly in hydromorphic soils where Fe redox chemistry can bring about important mineral transformations. While surface adsorption is well-known and widely studied, less attention had been devoted to the understanding of Fe-P coprecipitation, although it may greatly affect the extent, kinetics and mechanisms of retention of various P forms. In this work we synthesized Fe-P systems with increasing P/Fe ratio, prepared by either surface adsorption on ferrihydrite (Fh) or oxidative coprecipitation of Fe(II) with inorganic phosphate (Pi), inositol hexaphosphate (IHP) or phosphatidylcholine (PC). P and Fe contents, specific surface area (SSA), porosity, surface charge and particle size of the obtained materials were determined, while XRD, TEM, XPS and FT-IR techniques were used to study their properties. Coprecipitation resulted in a higher P retention with respect to adsorption. The presence of Pi reduced the rate of Fe precipitation with respect to the P-free system, resulting in nanometric particles with phosphate concentrated on the surface. With increasing Pi concentrations, more aggregated particles with a lower SSA and higher porosity were obtained. IHP conversely accelerated the precipitation of Fe through the formation of Fe-IHP complexes, leading to coprecipitates bearing IHP within the structure, as deduced from the less negative surface charge than the respective adsorbed systems (Fig. 1). The prevailing mechanism involved in PC interaction with Fe was instead physical retention, confirming the weaker stabilization of P diesters in soils. Irrespective of the P/Fe ratio, PC did not influence the rate of Fe(II) oxidation and precipitation, although its presence led to a decrease of SSA and pore volume. Coprecipitation of Fe(II) in the presence of P is therefore a more complex process than simple formation of a Fe(III)-hydroxide coupled with ion adsorption. Several processes may occur during Fe(II) oxidation, depending on the initial P/Fe ratio and P species. Our results also highlight the important contribution of coprecipitation to the stabilization and selective accumulation of IHP with respect to other P forms (as diesters) with important implications on its retention and bioavailability.

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Bacterial community diversity of Uruguayan soils from different soil map units with contrasting content of phosphorus and other edaphic properties

Silvia Garaycochea1, Elena Beyhaut1, Nora Altier1 1Instituto Nacional de Investigación Agropecuaria, Ruta 48 km, km 10 Rincón del Colorado.

Keywords: soil, bacterial community composition Soil microorganisms play key roles in the phosphorus (P) cycle, mediating the availability of this plant nutrient. Uruguay imports near to 100% of the P needed for agricultural activity; therefore, the search of more efficient production systems in the use of P is a challenge. Despite the high total P content in Uruguayan soils (150-700 ppm), the available P is relatively low (usually <10ppm), and independent of total P. The organic P fraction varies between 49 and 75% of the total P. Soil pH ranges from 5.1 to 7. The objectives of this study were: (1) to characterize the structural diversity and composition of the microbial communities in ten sampling sites, representative of five soil map units fromUruguay (I3A, SP, Tbo, TR, Y), and (2) to explore their relationship to soil physical and chemical properties. Taxonomical analysis was performed with QIIME pipeline and the statistical analysis were performed with Vegan and Phyloseq R packages.

Figure 1: NMDS plot of bacterial community with Permanova test

A total of 4547 OTUs were obtained. The dominant phyla along sites, with a prevalence up to 90%, were Proteobacteria, Actinobacteria, Verrucomicrobia, Planctomycetes, Chloroflexi and Firmicutes. The soil bacterial community richness and the Shannon index values showed significant differences among soil map units.

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The Canonical Component Analysis (CCA) allowed to narrow down to four the physicochemical soil properties that explained the bacterial diversity. The taxonomical bacterial community structures were best explained by a combination of pH, N, K and clay content. The NMDS analysis (Figure 1) showed the clustering of soils samples. Overall, our results suggest that soil physicochemical properties are among the driving forces of bacterial community diversity and composition. References - Ren B, Hu Y,Chen B, Zhang Y,Thiele J, Shi R, Liu M, Bu R (2017) Soil pH and plant diversity shape soil bacterial community structure in the active layer across the latitudinal gradients in continuous permafrost region of Northeastern China. Scientific Reports 8:5619 - Richardson A, Simpson R (2011) Soil microorganisms mediating phosphorous availability. Plant Physiology 156:989-996. - Wang X, Li H, Bezemer T, Hao Z (2016) Divers of bacterial beta diversity in two temperate forests. Ecol Res 31:57-64. - Yang F, Wu J, Zhang D, Chen Q, Zhang Q, Cheng X (2018) Soil bacterial community composition and diversity in relation to edaphic properties and plant traits in grassland of southern China Applied Soil Ecology

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Ammonium nitrogen application promoted inorganic phosphorus transformation and mobility in P-enriched calcareous soil

Shuai Zhang, Shuo Chen, Zhengjuan Yan, Bingqian Fan, Qing Chen Beijing Key Laboratory of Farmland Soil Pollution Prevention-control and Remediation; College of Resources and Environmental Sciences, China Agricultural University, No. 2 Yuanmingyuan

Xilu, Haidian, Beijing 100193, P. R. China.

Keywords: Ammonium nitrogen, inorganic phosphorus High applied rates of phosphorus(P), together with ammonium nitrogen(AN), had been commonly investigated in the intensive agricultural fields of North China, which resulted in high soil saturation of P and soil acidification induced by high AN application. However, the interaction of AN application on inorganic P(Pi) transformation and mobility is still unclearly understood. In this study, we measured the transformation of Pi in calcareous soil of long-term protected field and P mobility in the column leaching experiment with calcareous soil influenced by AN application. A sequential fractionation method proposed by Jiang and Gu (1989) and modified by Ronaghi et al. (2006) was used to fractionate soil Pi forms. Continuous annual application of AN fertilizer(urea) at the rates of 1688 kg N ha-1 significantly decreased the proportion of Ca8-P by 31.5% and increased the proportions of Fe-P and Al-P by 23-28% in 0-30 cm soil layer, and consequently increased Olsen-P and CaCl2-P contents in 30-90 cm soil layer. Soil acidification influenced the main factors on P transformation, including the decline in soil CaCO3, Mehlich-3 extractable Ca and Mg and increase in Mehlich-3 extractable Fe in 0-30 cm soil layer. However, the influences of AN fertilizer (urea or ammonium sulfate) application at the rate of 1500 mg N kg-1 soil on soil Pi transformation in the soil column leaching experiment with intermittent flooding were different from the trial of protected field. AN application significantly decreased Fe-P, O-P and Mehlich-3 extractable Fe, and increased the mobility of soil phosphate in the soil column, which implied that Fe-P and O-P was involved in soil ammonia oxidation process. Soil acidification dissolved soil calcium-associated P (Ca-P) and ammonia oxidation strengthened by the intermittent flooding released Fe-P (include O-P) in soil column leaching experiment, with high promotion in Pi leaching. The decrease in soil Ca-P and Fe-P (include O-P) after leaching were evidenced to support P transport to deep soil in P-enriched calcareous soil in the soil column leaching experiment. References Jiang B, Gu Y (1989) A suggested fractionation scheme of inorganic phosphorus in calcareous soils. Scientia Agricultura Sinica 20:159-165. Ronaghi A (2006) Inorganic Phosphorus Fractionation of Highly Calcareous Soils of Iran. Communications in Soil Science & Plant Analysis 37:1877-1888.

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Understanding the contribution of soil labile phosphorus forms to compromise agronomic and environmental thresholds

Bingqian Fan, Zhengjuan Yan, Shuo Chen, Shuai Zhang, Qing Chen Beijing Key Laboratory of Farmland Soil Pollution Prevention-control and Remediation; College of Resources and Environmental Sciences, China Agricultural University, No. 2 Yuanmingyuan

Xilu, Haidian, Beijing 100193, P. R. China.

Keywords: Phosphorus transformation, alum, dolomite High phosphorus (P) surplus sourced from heavy manure and P fertilizer application strengthened P mobilization in intensive agricultural fields (Huang et al., 2016; Yan et al., 2018). The relationship between agronomic indicator, i.e. Olsen-P and environmental indicator, i.e. water-extracted P (WEP) in our 202 of calcareous soil samples from Beijing had showed that WEP linearly increased more steeply with soil Olsen-P after exceeding “the changing point”. Therefore, it is fundamental to understand the contribution of soil labile P forms fractionated with Jiang and Gu method to the soil Olsen-P and WEP. In this study, two calcareous soils with soil Olsen-P lower “the change point” (LP, 52.6 mg kg-1) and over “the change point” (HP, 226 mg kg-1) were selected to fractionate soil P forms. The results showed soil Ca2-P, Ca8-P, and Al-P obviously increased with increasing soil Olsen-P and WEP, however, there were no changes in soil Fe-P, occluded-P and Ca10-P of LP and HP soils. Ca2-P form was the primary P pool of WEP in both soils while the forms of Ca2-P and Ca8-P were the main sources of Olsen-P in HP soil. In the P-stabilizing incubation experiment, HP soil was amended with alum and dolomite at different rates of 0, 0.5, 5, 10, 20, 50 g kg-1 soil, respectively, in order to reduce soil Olsen-P and WEP levels and measure P sorption isotherms after 90d incubation. Amending different rates of alum in HP soil significantly decreased the Olsen-P and WEP below the changing point due to the increasing transforming proportions of 2.8-68.9% Ca2-P and 4.5-88.5% of Ca8-P to Al-P; however, amending different rates of dolomite only decreased the WEP other than Olsen-P below the changing point; and when the added rate exceeding 5g kg-1, soil P sorption maxima and P buffer capacity were significantly increased. Although WEP declined, soil Olsen-P increased by dolomite amending due to the transforming proportions of 8.1-25.8% Ca8-P to Ca2-P. It was implied that dolomite amending performed more flexibly in controlling soil test P when compromising the environmental and agronomic P management. References - Huang L, Moore PA, Kleinman P J, Elkin KR, Savin MC, Pote DH, Edwards DR (2016) Reducing phosphorus runoff and leaching from poultry litter with alum: Twenty-year small plot and paired-watershed studies. Journal of Environment Quality 45:1413-1420. - Yan ZJ, Chen S, Dari B, Sihi D, Chen Q (2018) Phosphorus transformation response to soil properties changes induced by manure application in a calcareous soil. Geoderma 322: 163-171.

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Temporal changes in phosphorus forms in cultivated Scottish soils Andrew Tweedie1,2, Phillip Haygarth2, Anthony Edwards3, Allan Lilly1, Nikki Baggaley1, Marc

Stutter1 1The James Hutton Institute, Craigiebuckler, Aberdeen AB15 8QH

2Lancaster Environment Centre, Library Avenue, Lancaster University, Lancaster LA1 4YQ 3Scotland’s Rural College (SRUC), Ferguson Building, Craibstone Estate, Aberdeen AB21 9YA

Keywords Temporal, phosphorus, cycling Cycling of phosphorus (P) in modern agricultural soils is dominated by regular inputs of inorganic P fertilizer in each yearly growing season and removal of P in the crop. This in contrast to the tight recycling of P found in many natural systems related to its scarcity. However, in many cases the majority of agricultural P input is made unavailable to crops by soil chemical processes and microbial cycling. This is thought to have led to the build-up of P stocks and corresponding changes in the relative proportions of P species in these cultivated soils over a relatively short period of time (decades). These changes may negatively impact the capacity of these soils to deliver many eco-system services by disrupting the naturally developed nutrient cycling systems. We investigated the hypothesis that phosphorus forms and availability in agricultural soil have changed over a period of rapid agricultural intensification. Geographically paired samples of soil from 34 agricultural sites in North East (NE) Scotland was collected at two timepoints. The first samples were taken between 1951 and 1981 and in all cases the resampling took place in the autumn of 2017. The set of soils sampled was representative of the range of cultivated soils in NE Scotland. Soil extractions were performed including a national agronomic P index test, also N, P and DOC forms by water extraction and Fe, Al, P by the stronger extractant acid ammonium oxalate to investigate the soil P exchange complex. Concentrations of Al, Fe and P by acid ammonium oxalate extraction were not found to have changed between the two time points. However, in water extractions inorganic phosphate concentrations were found to have increased and organic P decreased. Statistically significant reductions in concentrations of both DOC and N were also detected in water extracts over time. These results show that changes in P in cultivated soil are detectable between the two timepoints under certain extraction conditions. Further work will include extraction by NaOH-EDTA and subsequent 31P NMR analysis of organic P forms. Knowledge of the P-cycling response of soils under agricultural land-use over periods of decades as provided by this dataset, provides an opportunity to understand changes in soil nutrient concentrations, balances and availability and inform studies seeking to improve the sustainable management of soil fertility.

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The role of phosphine production within the soil system Anchen P. Kehler1, Martin S.A. Blackwell1, Philip M. Haygarth2, Adrian Guy3, Federica

Tamburini4 1Rothamsted Research, North Wyke, Okehampton, Devon, EX20 2SB, UK

2Lancaster University, Bailrigg, Lancaster, LA1 4YW, UK 3Elemental Digest Systems Limited, Southgate House, 59 Magdalen Street, Exeter, Devon, EX2

4HY, UK 4 ETH Zürich, Rämistrasse 101, 8092 Zürich, Switzerland

Keywords: Phosphine, soil, cycling The occurrence of phosphine in the natural environment and its role in the biogeochemical cycling of phosphorus has been in debate for many years, due to difficulties in determination and characterizing ambient biogenic production. It is generally understood that microbial activity is a key factor for the release of natural phosphine gas into our atmosphere at the soil-air interface. However, chemical and microbial pathways for its formation are poorly characterized. Despite phosphine already being linked to the greenhouse effect, as well as having regular interactions with prominent greenhouse gases such as carbon dioxide and methane, we are mostly unaware of the environmental significance of phosphine or how likely it is going to become in the coming years.

This PhD project is in its early stages and is testing the hypothesis that methods of biological phosphine production are dominant over chemical mechanisms. It also has a secondary objective of identifying the optimal conditions for the natural production of phosphine in soils. To achieve this, I aim to optimize a methodology for the capture and analysis of natural phosphine gas (Figure 1) so that phosphine production in agricultural and natural systems in the UK can be quantified. The ultimate goal is to revise the conceptual model for the soil phosphorus cycle with a quantitative estimation of the role of phosphine formation in soils and the underlying controlling mechanisms.

Figure 1: Experimental bubbler apparatus for the trapping of phosphine gas

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Changes in crop residue phosphorus speciation and bioavailability with combustion

Terry Rose1, Lukas Van Zwieten2, Rachel Wood2, Michael Rose2, Cassandra Schefe3, Lei Liu1, Andrew Rose4

1Southern Cross Plant Science, Southern Cross University, Australia 2NSW Department of Primary Industries, Australia

3Schefe Consulting, Australia 4School of Environmental Science and Engineering, Southern Cross University, Australia

Keywords: Ash, Hedley fractionation, XANES

Despite the prevalence of fire in both natural and managed ecosystems, changes in phosphorus speciation due to combustion of plant material are poorly understood. The consequences of such changes on the bioavailability of the residual phosphorus and its potential to contribute to eutrophication are therefore unknown. Here, we used X-ray Absorption Near Edge Structure spectroscopy to resolve the major phosphorus species in unburnt rice straw and in the residue from rice straw combusted at temperatures up to 900°C, and related the observed changes in phosphorus speciation to the potential phosphorus bioavailability using selective chemical extraction techniques as a proxy. We subsequently investigated the bioavailability of P in ash using 33P-labelled rice straw in a ryegrass bioassay study. XANES spectra indicated that organic phosphorus was present in unburnt residue but was not present beyond 400°C. Calcium phosphates were generally the predominant species across all temperatures, although the presence of potassium phosphates increased beyond 300°C. XANES spectra also suggested the presence of pyrophosphates at and above 500°C, and this corresponded to an increase in the molybdate-unreactive NaOH-extractable P fraction at 500 and 600°C, and an increase in the molybdate-unreactive HCl-extractable P fraction beyond 600°C using the Hedley fractionation scheme. Water-soluble molybdate-reactive P (inorganic P) declined sharply beyond 200°C as the HCl-extractable inorganic P increased. Citric acid-extractable P (used to assess fertiliser value) declined from around 1.8 g/kg at 100°C to around 1.3 g/kg at 200°C but increased to > 2 g/kg at combustion temperatures of 500-800°C. The results suggest that while Ca-phosphates were the dominant P form at all combustion temperatures, the type of Ca-phosphates formed at higher temperatures have lower water solubility are soluble in both HCl and citric acid, and are presumably bioavailable.

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Figure 1: P speciation in rice straw combusted at different temperatures based on the Hedley sequential fractionation method. A. Molybdate reactive P (orange = water extractable P, green = NaHCO3 extractable P, blue = NaOH extractable P, and purple = HCl extractable P). B. Non-molybdate reactive P (orange = water extractable P, green = NaHCO3 extractable P, blue = NaOH extractable P, and purple = HCl extractable P). C. Total P (red = molybdate reactive P and green = non-molybdate reactive P). Symbols represent the mean and error bars the standard error of the mean from triplicate samples.

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Control of biotic and abiotic processes on phosphorus availability in acidic P-limited soil: 33P tracer assessment Deejay Maranguit1*, Nataliya Bilyera 2, Yakov Kuzyakov 3

1Dept. of Soil Science, Visayas State University, Baybay, 6521-A Leyte, Philippines 2Dept. of Radiobiology and Radioecology, National University of Life and Environmental

Sciences of Ukraine, 03041, Kyiv Ukraine 3Agro-Technological Institute, RUDN University, 117198 Moscow, Russia

Keywords: 33P isotopic labeling; Microbial biomass P; Sorption-desorption 33P labeling has high sensitivity to trace soil P dynamics and the fate of added P fertilizers across various P pools. Nonetheless, only a few studies used this approach. This study was designed to investigate the P dynamics and to assess the effects of biological and physicochemical processes on P availability in acidic P-limited soil. We followed the incorporation of 33P-labeled KH2PO4 in available P (PAEM), microbial biomass P (Pmic) and Fe/Al-bound P (PNaOH) pools in Cambisol amended with glucose and ammonium sulfate as carbon and nitrogen sources, respectively. The experiment was full factorial, composed of 12 experimental units. The main factor was the rate of P addition: 0%, 10% and 50% of the initial total P content. Each P level was amended with the following (second factor): (1) glucose as a C source in a one-time (50 µg g-1) and staggered (10 µg g-1 x 5 days) application, (2) ammonium sulfate (50 µg g-1) as an N source and (3) distilled water (control). Fast and almost instantaneous P fixation by the Fe and Al oxides and immobilization by microbial uptake were recorded. As much as 10-20% of the applied 33P was recovered in the Pmic pool after 120 h. Applying glucose as a C source boosts microbial activity, growth and demand for P, resulting in increased 33P recovery and P content in the microbial pool in soils with high P addition. The negative relationship between Pmic and PAEM (R2 = 0.46) in P-amended soils suggests that P availability is strongly influenced by microbial P uptake. The high recovery of applied 33P (45% of applied 33P) in PNaOH and the strong negative relationship (R2 = 90-96) between PNaOH and PAEM

show the dominance of P adsorption by Fe and Al oxides on the fate of P in acidic P-limited soil. The P pools measured by sequential extraction and the P exchange and fluxes between pools are strongly controlled both by physicochemical factors, i.e. sorption and by biological reactions, i.e. immobilization. These two process groups – biotic (microbial P immobilization) and abiotic (sorption) – sustain long-term P fertility after the turnover of microbial biomass and desorption of fixed P, respectively.

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Increased soil organic carbon enhances soil microbial biomass of phosphorus Yi Peng1, Gu Feng1

1 College of Resources and Environmental Sciences, China Agricultural University

Keywords: MBP, soil organic carbon, C:P ratio Suboptimal phosphorus (P) availability is a primary limiting factor to agricultural production, due to the sorption and sedimentation of P in soil and less availability to plant uptake. Soil organic carbon (SOC) and microbial biomass phosphorus (MBP) are closely associated with soil P cycling, and MBP is a potentially available P pool in soil P cycling and mediates the availability of P to plants. Microorganisms can immobilize large amounts of phosphorus in their biomass, and there is carbon limitation of microorganisms in farmland soil. Our hypothesis is that increasing the soil organic carbon can enhance soil MBP. Soil samples were collected from three long-term experimental sites at Red Soil Experimental Station in Qiyang, Hunan province, Loessial Soil Experimental Station in Yangling, Shaanxi province, and Grey Desert Soil Experimental Station in Urumqi, Xinjiang province. The SOC, soil Olsen P, MBP, and microbial biomass carbon (MBC) were measured, and the relationship between SOC and MBP was investigated. Results showed that the increase of SOC by one unit (g kg-1) lead to the improvement of MBP by 3.3, 3.7 and 1.3 mg kg-1 in the red, loessial and gray desert soils, respectively. There was significant relationship between the changes of SOC and that of MBC. Soil MBP was enhanced with the increasing of soil MBC. There was a weak and positive relationship between the C:P ratio of microbes (MBC/MBP) and that of resources (SOC/Olsen P) (slope = 0.20; P < 0.01). The slope smaller than 0.25 indicated the C:P homeostasis of the microbial community across the three types of soil, although it was not a strict homeostasis. This suggested MBC could be improved with the increasing of SOC, with the C:P homeostasis of the microbial community, which need assimilate more soil P to maintain the proportion of stable elements. Therefore, it is an effective way to improve MBP through the increase of SOC.

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Impact of earthworm activity on the P mobilization under willows in a short rotation coppice

Anika Zacher1, Laura Köhn1, Christel Baum1, Petra Kahle2, Stefan Koch2, Akane Chiba3,4, Michael Schloter3,4, Peter Leinweber1

1Soil Science, University of Rostock, Justus-von-Liebig Weg 6, 18059 Rostock, Germany 2Natural Resources Conservation and Soil physics, University of Rostock, Justus-von-Liebig Weg

6, 18059 Rostock, Germany 3 Research Unit Comparative Microbiome Analysis, Helmholtz Zentrum München, Ingolstädter

Landstraße 1, 85764 Neuherberg, Germany 4Technische Universität München, TUM Chair of Soil Science, Emil-Erlenmeyer-Forum 2, 85354

München, Germany

Keywords: biopores, drilosphere, phosphatases

Earthworms are key players of bioturbation in soils and promote the soil microbial activity by aeration, addition of organic matter into soil and by their formation of crumbs. For these reasons, they also affect the P cycling in the soil. However, the magnitudes of these impacts on the controls of P mobilization are not known so far. Therefore, the impacts of earthworm activities on chemical, microbiological and physical controls of P mobilization in soil were investigated using a short rotation coppice with willows (Salix spp.) at a Stagnic Cambisol in Northern Germany as model test site. It was assumed that the no-till management of these perennial crops promote the earthworm colonization and thereby increase their impact. This was confirmed by a high number of biopores in both the top- and subsoil. The general microbial activity and the activities of soil enzymes involved in the P mobilization (acid phosphatase and β-glucosidase) were significantly higher in the drilosphere than in the bulk soil both in top- and subsoil. Furthermore, the concentration of easily plant-available P was significantly increased in earthworm droppings compared to the bulk soil. The impact of the drilosphere on P mobilization was generally stronger in the subsoil than in the topsoil. In conclusion, a significant promotion of P mobilization and consequently improved plant-availability of P were assumed in soils with high earthworm abundance. However, an increased risk of P losses into the groundwater was indicated in high biopore density.

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Phosphate desorption dynamics in Swedish agricultural soils after long-term phosphorus fertilization

Sabina Braun, J.R. Marius Tuyishime, Jon Petter Gustafsson

Department of Soil and Environment, Swedish University of Agricultural Sciences (SLU), Box 7014, 750 07 Uppsala, Sweden

Keywords: Phosphate desorption, Pi filter method, fertility experiments Understanding the dynamics of phosphorus (P) desorption in agricultural soil is a key to understanding plant P uptake and P leaching. This study aimed to investigate how desorption of soil P in the presence of a sink was affected by 1) long-term P fertilization, 2) soil properties and 3) P speciation. Soil samples were subjected to continuous P depletion by the Pi paper method (van Rotterdam et al. 2009), in which iron oxide-coated filter papers were immersed in 0.005 M CaCl2 soil suspensions and replaced 10-15 times over 20-30 days (depending on the soil). All soils were from the Swedish long-term fertility experiments and received either no P or a large surplus of P during 50 years of cropping. Soil properties such as pH, clay content, oxalate extractable iron and aluminum etc. were determined. Phosphorus speciation was investigated by P K-edge XANES spectroscopy. A multiple regression model for predicting desorption rate using soil properties was developed after stepwise elimination. The results show that the cumulative amount of P extracted by Pi papers exceeded the amount of P extracted by the Olsen method after only a few exchanges for both fertilized and unfertilized soils. For most of the soils the Pi papers were not able to reach the amount of P extracted by the acidic AL extraction. However, the cumulative desorption curves (Figure 1a) showed that all soils continued to deliver P to the Pi papers until the end of the experiment and that no plateau was reached. The desorption curve was log-transformed (Figure 1b), and the slope could be predicted with; slope=0.5029 + 0.0009*Fe ox (mmol/kg) – 0.0121*P-CaCl2 (mmol/kg) – 0.0018*clay (%), (adjusted R2=0.70). A paired t-test showed that the slope of the desorption curves were significantly (p<0.05) steeper for the fertilized treatments. This results indicate that a combination of soil P tests and selected soil properties can provide a realistic assessment of the soil's ability to deliver P to plants and that the soils fertilization history affects the desorption rate of P. Reference van Rotterdam AMD, Temminghoff EJM, Schenkeveld WDL, Hiemstra T, van Riemsdijk WH (2009) Phosphorus removal from soil using Fe oxide-impregnated paper: processes and applications. Geoderma 151:282-289.

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Figure 1: Example of a phosphate desorption curve for an agricultural soil (Ekebo) as obtained with the Pi paper method.

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Characterization of the available P of various digestates using Fourier transform mid-infrared photoacoustic spectroscopy

Jing Huang1, Sander Bruun1, Nadia Glæsner1, Jin Mi Triolo2 1Plant and Soil Science Section, Department of Plant and Environmental Sciences, Faculty of

Science, University of Copenhagen, Thorvaldsensvej 40, Frederiksberg C, DK-1871, Denmark.

2Institute of Chemical Engineering, Biotechnology and Environmental Technology, Faculty of Engineering, University of Southern Denmark, Campusvej 55, Odense M DK-5230, Denmark

Keywords: FTIR-PAS, Digestate, Water-extractable P Anaerobic digestion has become an effective and widely applied technology for waste treatment, which can produce renewable energy-biogas. As a by-product of anaerobic digestion, digestate has rich plant nutrients such as nitrogen, potassium and phosphorus (P), which could be used as soil amendment or fertilizer. To evaluate both the P fertilizer value of digestates and tp avoid excessive P addition to agricultural fields, mainly causing eutrophication of surface waters, it is of relevance to know the characteristics of P availability in different digestates before soil application. Water-extractable P (WEP) has been proved as an effective indicator of plant available P associated with soil amendments and of dissolved P loss in runoff. Moreover, the ratio of WEP and total P (WEP/TP) can be a more direct comparison of the lability of the phosphorus in different biowates. Therefore, the aim of this study is to 1) use the fourier transform mid-infrared photoacoustic spectroscopy (FTIR-PAS) as a rapid and non-destructive method for predicting the P availability of different digestates and 2) identify the chemical structures related to available P from FTIR-PA spectra. The FTIR-PA spectra of different kinds of digestates both collected from laboratory-scale digesters and biogas plants were measured and the partial least square (PLS) regression method was used to develop prediction models. The preliminary results show that both WEP and WEP/TP can be predicted using FTIR-PAS according to R2 values and the ratios of performance to deviation (RPD) with different pre-processing treatments and furthermore of identifying the chemical compounds that are correlated with the available P will be discussed.

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Characterization of P solubility and plant availability in various secondary raw materials with equilibrium and sink-based extractions

Olivier Duboc, Jakob Santner, Franz Zehetner, Gerhard Soja, Christoph Pfeifer, Walter W. Wenzel

University of Natural Resources and Life Sciences, Institute of Soil Research, Konrad-Lorenz-Strasse 24, 3430 Tulln, Austria.

Keywords: Recycling, Fertilizer, Phytoavailability Due to the limitation of global P reserves, recycling fertilizers produced from heterogeneous secondary raw materials such as municipal sewage sludge (MSS), slaughterhouse waste or animal manures are becoming increasingly relevant. Various waste treatment processes further increase the diversity of products. We have previously shown that an infinite-sink extraction based on ferrihydrite-filled dialysis bags provides a better estimate of the plant available P fraction in chemically diverse fertilizer materials than existing equilibrium extractions (e.g. H2O, neutral ammonium citrate) (Duboc et al. 2017). Following up on these preliminary results, we are conducting further measurements of P solubility / extractability in various secondary raw materials and their conversion products. The objectives are (1) to build a reference base by characterizing a representative selection of P recycling materials and reference fertilizers and (2) to enhance our understanding of the benefits of different conversion processes. To this end, we use (1) the dialysis bag infinite-sink method as an estimate of the plant-available P quantity, and (2) the H2O extraction (30 min, 1:100 w:v) to determine readily soluble P. So far, our results indicate that P in carbonized animal manure (pyrolysis, hydrothermal carbonization) has a lower solubility than in their respective feedstocks. This may be due to the initial hydrophobicity of the carbonized product. Contrastingly, the plant available P quantity was either enhanced or remained unaffected. Products based on conversion of municipal sewage sludge exhibit a very low P solubility, and a very wide range of P plant availabilities ranging from ~10% (MSS-ash and -biochars) to 90% for more advanced types of MSS treatment processes. Overall, our results suggest that carbonization either increases or does not substantially affect the P availability to plants, and that MSS conversion products can be at par with conventional fertilizers. Initial low P solubility for the majority of converted products is a potential advantage compared to conventional fertilizers in terms of environmental impact (leaching / runoff) and nutrient use efficiency in agriculture. Combining infinite-sink and H2O extraction provides a promising toolbox for product development and assessment in the context of diversifying source materials, fertilizer applications and markets. References Duboc O, Santner J, Golestani Fard A, et al (2017) Predicting phosphorus availability from chemically diverse conventional and recycling fertilizers. Sci Total Environ 599–600:1160–1170. doi: 10.1016/j.scitotenv.2017.05.054.

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Phosphorus fractions in the soil profile as affected by long-term fertilizer practice

Bettina Eichler-Löbermann, Paul Winklhofer, Theresa Zicker, and Ralf Uptmoor University of Rostock, Chair of Agronomy and Crop Science, J. von Liebig Weg 6, 19059 Rostock,

Germany

Keywords: P fractions, compost, subsoil Long-term field experiments can give an extensive overview about the effectiveness of fertilizer strategies also considering the influence of annual environmental conditions, nutrient mobilization and translocation processes in soil. At the Rostock long-term field experiment the effects of single and combined organic and inorganic phosphorus (P) treatments (in total nine treatments) on soil P pools and plant nutrition are investigated since 1998. For this study on P fractions (after Hedley) we selected the following treatments: I) Control without any P, II) Triplesuper P (TSP), III) biowaste compost, and IV) TSP + biowaste compost. Single application of TSP and compost was adapted to the P removals due to plant´s harvest. Following, combined TSP + compost application resulted in increasingly positive P budgets during the experimental time. Soil samples were taken from the topsoil (0-30 cm) in 1999, 2003, 2008, 2012, and 2017 as well as from the subsoil 1 (30-60 cm) and subsoil 2 (60-90 cm) in 2012 and 2017. The P treatments resulted in different crop P uptakes and strongly influenced the soil P fractions in the top soil. The amount of P applied had a greater effect than the type of the P source. Higher P concentrations after P supply in comparison to the control were also found in the subsoil 1. Here the labile and moderate labile fractions (P-water, P-NaHCO3, P-NaOH) were mainly increased after TSP application and the stabile fractions (P-H2SO4, P-residual) were mainly increased in the combined treatment with high P surplus. Also in sub soil 2 higher P concentrations in the labile P fractions were found in the treatments with TSP application, whereat it did no matter if TSP was applied alone or combined with compost. The P budgets could not fully explain changes of soil P pools at each sampling date. Beside vertical movements of P we also expect surface run-off and transformation of soil P fractions.

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Phosphorus dynamic in soil amended with cattle dung and cow dung breakdown model in soil

Maria de la Luz Mora1,Carolina Shene1, Barbara Fuentes2, Marcela Calabi1, Rolando Demanet1 1Center of Plant, Soil Interaction, and Natural Resources Biotechnology, Scientific and

Technological Bioresource Nucleus (BIOREN), Universidad de La Frontera, Temuco, Chile. 2Universidad Católica del Norte, Antofagasta, Chile.

Keywords: Soil phosphorus fraction, cattle dung

In Chilean volcanic soils, more than the 50% of the total Phosphorus (PT) is found as

organic P (Po), specially as recalcitrant P (inositol, penta- and hexa-phosphates,

representing from 40 to 80% of PT and its content in Chilean Andisols averages over

2,000 mg kg-1. The effects of applying fresh cow dung on P-fractions in soil profile,

and other related soil properties (pH, aluminum, ammonium and nitrate) in an acid

Chilean Andisol were studied. Soil P-fractions were monitored for six months in soil

columns which received cattle dung on the surface. In the second experiment bag

soil incubation with fresh cow dung were incubated for 60 days. In columns, soil pH,

and phosphate concentration increased in 0-10 cm fraction at 30 days. After this

period the pH decreased from 5.4 to 4.9 at the same depth. Plant available P-fraction

(P-NaHCO3) fraction increased (69-72 mg kg-1) in day 60. Then this fraction showed

a decreased of 10 mg kg-1, due to microbial activity and pH change. From the 120 to

180 days the P-NaHCO3 fraction recovered its original level. P-NaOH fraction

decreased according to soil depth; this was correlated to the sonicated P-NaOH

fraction (ocluded) increase. P-residual increased to 100 mg kg-1 at 40-60 cm depth

soil. P-HCl fraction decreased significantly (p<0.01) at all depths from 10 to 5 mg kg-

1.

Figure 1. Soil column with cattle dung: Effect on phosphorus fractions in soil profile.

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Only an organic P-form was found (5-10 mg ml-1); in the leaching solution. 31P RMN

indicated that this is an orthophosphate diester. Results showed P diffusion and

fixation from 0-10 cm toward 30-60 cm, because of the less organic matter content.

A mathematical model for describing the P dynamic is proposed. Its parameters were

calculated using the experimental data. No significant differences (p>0.05) were

observed between experimental and calculated values of P-labile fraction, P-NaOH,

sonicated P-NaOH. However, the model was not able to simulate the behavior of P-

HCl and P-residual fractions. This work, showed that P was stored in less available

fractions such as P-Al and Fe sonicated P-NaOH and P-residual. But, soil incubation

with catle dung and nitrogen plus glucose assay showed an increment on

phosphatase activity enhancing labil P and decreasing residual P fraction content in

soil. The reintegration of residual soil P and recycled sources of P to the global P cycle

would be considered an effective solution to affront the growing demands for this

non-renewable resource in grassland soils but we must to consider the C:N:P

stoichiometry management .

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Effects of different P fertilizer amendments and inoculation with mycorrhizal fungi on P forms in a maize field determined by 31P-NMR spectroscopy

Vincenza Cozzolino1, Hiarhi Monda2, Pierluigi Mazzei2, Vincenzo Di Meo1, Alessandro Piccolo1,2

1Department of Agricultural Sciences, University of Naples, Federico II, Portici, Naples, Italy 2Interdepartmental Research Centre CERMANU, University of Naples Federico II, Portici, Italy

Keywords: P legacy, diesters, sustainable agriculture

Inefficiency of fertilizer phosphorus (P) use in agricultural soils is often associated

with accumulation of inorganic and organic P in fertilized soils. The legacy soil P may

represent a large soil P pool and could help preserve critical reserve of mineral P to

ensure future food production. Attention has been also devoted to arbuscular

mycorrhizal fungi inocula to improve plant performance and P use efficiency.

However, the chemical nature of soil P forms accumulated and their dynamics in

agricultural soils under different fertilizer treatments in combination with AMF

inoculation are still poor investigated.

Therefore, our objective was to use solution 31P nuclear magnetic resonance (NMR)

spectroscopy on sodium hydroxide–ethylenediaminetetraacetic acid (NaOH-EDTA)

extracts to identify the chemical nature of organic P in soils from a medium-term (5

years) maize field experiment. This include three different P fertilizer treatments

(without P, P0, mineral P, TSP, composted manure, CP) in combination with and

without inoculation (M+, M-) with a commercial AMF inocula. Furthermore, we

evaluated grain yield, grain N and P concentration, available soil P concentration

(Olsen method) and total soil P (inorganic and organic) by ignition-H2SO4 method.

Although available soil P showed the smallest value in P0 treatment, the kind of

fertilizer treatment had no significant effect on grain yield and grain P concentration,

whereas inoculation influenced only grain N concentration in P0 e TSP fertilizer

treatments (40% increase). The addition of compost (CP) in M-and M+ increased

total soil P concentration as compared to P0 and TSP treatments, but P0 revealed

the greatest value and percentage of total organic P (Po).

NMR spectra showed that the type of P fertilizer, affected the abundance and the

composition of organic P forms, whereas inoculation with AMF had no significant

effects. For all treatments, the most dominant organic P form was monoester group

(13-20%of total P) following diesters (1.2-3%). The greatest percentage of diesters

and diesters: monoesters ratio values were observed in P0 treatments. Inorganic

available P deficits could trigger microbial growth and activity, inducing a fast P

cycling. These results could be important to provide a theoretical basis to reduce P

fertilization, thereby realizing the potential of soil legacy P thus enhancing the P

fertilizer use efficiency in agricultural soils.

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Status of soil test P across Agassiz research farm in British Columbia, Canada Aimé J. Messiga1, Bittman Shabtai, Hunt Derek, Dennis Haak, Thomas W. Ben

1Agriculture and Agri-Food Canada, PO Box 1000, 6947 Highway 7, Agassiz, BC, Canada.

Keywords: Agassiz Research Farm, Legacy soil P In Canada, the Fraser Valley is the most intensively managed agricultural landscape with the highest livestock per unit area. This region is also home to 70% of the dairy cows in British Columbia (BC) and the dairy industry ranks first among the top contributors to the total provincial farm cash receipts with a 19% share out of $3,075.8 million in 2015 (BC Ministry of Agriculture (BCMA), 2016). Past and on-going nutrient management practices particularly P fertilization are placing a burden on the public and agricultural sector in the region. Land applications of farm manure based on crop N needs simultaneously with large inputs of mineral fertilizer P have contributed to over- P fertilization compared with crop removals. The objective of this study is to present a snapshot of soil test P in the long-term managed fields of the Agassiz research station, Agriculture and Agri-Food Canada. The land is used for research and corn and grass production for feed production to support a Dairy Centre. Composite soil samples were collected in fall 2017 across 26 fields (10 under corn, 2 under corn/grass, and 14 under grass) before the first rainfall down the soil profile (0-15, 15-30, and 30-60 cm) and analyzed for Kelowna extractable P, the conventional soil test method in region. The concentration of Kelowna extractable P in the 0-15 cm depth varied between 27 and 94 mg kg–1 under corn fields, 55 to 93 mg kg–1 under corn/grass fields, and 12 to 126 mg kg–1 under grass fields. The concentration of Kelowna extractable P in the 15-30 cm depth varied between 17 and 66 mg kg–1 under corn fields, 61 to 80 mg kg–1 under corn/grass fields, and 12 to 67 mg kg–1 under grass fields. The concentration of Kelowna extractable P in the 30-60 cm depth varied between 9 and 33 mg kg–1 under corn fields, 22 to 28 mg kg–1 under corn/grass fields, and 6 to 37 mg kg–1 under grass fields. On average, six fields including corn (2), grass (3), corn/grass (1) productions showed Kelowna P values above the excess class (> 80 mg kg–1) according to local recommendations. These fields also showed the highest Kelowna P concentrations at depth 15-30 cm indicating potential downward movement of P. We conclude that fertilization practices in corn and grass production systems at Agassiz Research Farm including manure application rates resulted in build-up of legacy soil P with time. References British Columbia Ministry of Agriculture 2014. British Columbia Agrifood Industry Year in Review 2014. 28p

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Status of legacy soil P in agricultural fields in the Hullcar Valley, Canada Aime J. Messiga1, David Poon, Laura Code, Noura Ziadi

1Agriculture and Agri-Food Canada, PO Box 1000, 6947 Highway 7, Agassiz, BC, Canada.

Keywords: Hullcar Valley, Legacy soil P

The Hullcar Valley located in the North Okanagan is characterized by an intensive beef and dairy production. The objective of this study is to present the status and distribution of legacy soil P in four Benchmarks sites selected in the Hullcar Valley. Soils in most of the study area are well to rapidly-drained soils, in the Chernozemic or Brunisolic soil orders, and there are small areas of poorly-drained Gleysolic or Organic soils (Poon et al., 2017). Soil samples were collected at 0-30 cm, 30-60 cm and 60-90 cm depth in four sites cropped with silage corn (sites #10 and #34) and alfalfa (sites #23 and #37) in Mid-October 2016 and Mid-April 2017 and analyzed for Mehlich-3 extractable P and other cations. Mehlich-3 P (PM3) and P saturation index [PSI, (P/Al)M3] in the 0-30 cm soil depth were higher in corn sites compared with alfalfa sites. Mehlich-3 extractable P in the 0-30 cm depth was 159 mg kg–1 in site # 10 and 116 mg kg–1 in site #34, but 139 mg kg–1 in site #23 and 96 mg kg–1 in site # 37. The PSI in the 0-30 cm depth was 26% in sites #10 and #34, but 18% in site #23 and 15% in site #37. Mehlich-3 extractable P and PSI decreased with depth at all sites, but #37 where higher concentrations were obtained at 60-90 cm (PM3 = 82 mg kg–1 and PSI = 31%) compared with the layer above (30-60 cm, PM3 = 56 mg kg–1 and PSI = 9.3%) indicating a downward movement of P from the upper layer in this site. Results of the benchmark testing indicate that soil test P values in the Hullcar Valley are above the excess class according to local recommendations suggesting that fertilization practices including manure application rates resulted in build-up of legacy soil P with time. References Poon, D, Code L (2017). Tracking Post-Harvest Soil Nitrate in Agricultural Fields in the Hullcar Valley. Final Report. BC Ministry of Agriculture, 28p.

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Multiannual dynamics of P-ions in solution in two French cropped soils after repeated applications of organic waste products

Christian Morel1, Sabine Houot2, Denis Montenach3, Alain Mollier1 1 INRA, UMR ISPA, 33140, F-33883 Villenave d’Ornon, France; Bordeaux Sciences Agro, 33170

Gradignan, France; 2 INRA, ECOSYS, 78850 Thiverval-Grignon, France ; 3 INRA, SEAV 0871, 68021 Colmar, France

Keywords: Organic recycling, P fertilization, P budget Organic waste products (PRO) represent significant phosphorus (P) sources in France, but their availability to plants is rather unknown, in particular at the field scale applied at realistic doses. The P in PRO is mainly under mineral forms. After spreading, part of their total-P is released into the soil solution as orthophosphate ions (H2PO4

-, HPO42-), denoted by P-ions, which modifies the equilibrium at the solid-

to-solution interface. Dissolved P-ions are of crucial importance since they are the forms absorbed by plant roots. This study reported the impact of repeated applications of different PRO on the multiyear dynamics of P-ions in relation with P budget between applied P and exported P in crops harvests. Two French field experiments on PRO were analyzed: QualiAgro (INRA-Veolia) on a neutral glossic Luvisol with silt loam texture; PROspective (INRA-Colmar) on a deep Calcaric Cambisol (11% CaCO3, pH = 8.2). Both trials included control treatments that do not receive P. Both experiments included a dairy cow manure (FUM), a co-compost of green waste and urban sludge (DVB), and a bio-waste compost (BIOD). A residual household waste compost (OMR) is also applied in QualiAgro and an urban sludge (BOUE) and the composted manure (FUMC) in PROspective. The spreading was managed on a basis of 4 t C ha-1 at QualiAgro and 170 kg total N ha-1 at PROspective applied every two years. Treatments were repeated 4 times. Yields and their P content were yearly measured in each plots. Soils from the plowed layer were sampled every two years, air dried, sieved (2 mm) and stored. Both P-ions concentration ions in solution (Cp), and associated transfer of P-ions by diffusion at the solid-to-solution were determined.

The cumulated P budget was analytically verified within the soil plowed layer in both trials. The missing few percents were located in the few centimeters of soil just beyond the plough depth. The initial Cp was 1.04 and 0.69 mg P L-1 at QualiAgro and PROspective, respectively. Its decrease was faster with negative P budget in TEM-PROspective than in TEM-Qualiagro TEM (1.8 and 1.1 (μg P L-1) (kg P ha-1) -1, respectively) in relation with P-ions diffusion capacity from soil to solution. The different Cp dynamics after applying P-PRO can be explained by the combined effects of P speciation in PRO, diffusive P-ions transfer at the solid-to-solution interface in relation with physical-chemical soil properties. For example, the presence of apatite in some PRO, such as BIOD, explaine the drastic decrease in Cp in the carbonated soil.

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Fig. 1. Multiannual dynamics of P-ions concentration in solution for QualiAgro (left) and PROspective (right) field experiments dedicated to the study of organic wastes products

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Enhancing phosphorus availability and mitigating the toxicity Dharani Dhar Patra

Bidhan Chandra Chandra Krishi Viswavidyalaya

Mohanpur, Nadia, West Bengal, India.

Keywords: PSM, Microbial inoculants, P toxicity

Phosphorus is one of the most important elements, after nitrogen in crop production. The P content in Indian soil is about 0.05% and a very low amount (0.1%) of the P present in soil is available because of number of chemical and physic-chemical properties. Phosphorus plays a significant role, in root development, providing vitality and resistance and seed formation of some crops, and early maturation of many crops. Synthesis of chemical P fertilizer is an expensive proposition; major portion of P is fixed in the soil, which has a long term adverse influence in terms of several ill effects. Soil microbes play a vital role in transformation/ solubilization of P and subsequently its availability to plants. Microorganisms solubilize and mineralize P from the fixed form of soil P. Phosphate solubilizing microorganisms (PSM) play a significant role in enhancing P solubility, crop production and sustaining soil fertility. An extensive and consistent research effect is in the offing for development and distribution of better quality inoculants to the users. Researchers have a great responsibility to the society to find ways and means as to how soil P availability could be improved, by development of superior microbial inoculants through genetic engineering of specific organisms. This paper focuses on the diversity of PSM mechanisms of P solubility and availability, role of P enzymes and different edaphic factors on solubility for managing sustainability. The paper also depicts the toxicity of P in soil-plant system and its mitigation.

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Compound specific phosphate desorption in acid sandy soils at different degrees of phosphate saturation

Jiayi Jiang1, Lisa Mabilde2, Qing Chen1, Stefaan De Neve2, Steven Sleutel 2 1College of Resources and Environmental Sciences, China Agricultural University, No. 2

Yuanmingyuan Xilu, Haidian, Beijing 100193, P. R. China. 2 Department of Environment, Faculty of Bioscience Engineering, Ghent University, Coupure

Links 653, 9000 Gent, Belgium.

Keywords: PSD, competitive P (de)sorption, acidic sandy soils Phosphate saturation and leaching from arable land is currently the main environmental concern in agriculture in Flanders (Belgium). High P leaching from soils may be stimulated by high organic matter content as a result of competition for binding sites in soil. We designed an experiment to assess the importance of such competition between specific organic compounds and phosphate for sorption sites in soil, using a judicious selection of soils from a database of an extensive soil P saturation survey. This selection consisted of 3 sets of light textured soils from three levels of phosphate saturation degree (PSD), namely High > 55%, Medium 30%-40% and Low < 10% PSD, and that had very similar pH, organic matter, and content of oxalate extractable Al/Fe. Batch experiments were conducted to evaluate the possible desorption of phosphate by carbohydrates (glucose), fatty acids (octanoic acid) and phenolic compounds (guaiacol). Preliminary results indicated that, glucose and octanoic acid both increased P desorption with the concentration in high and medium PSD soils, but resulted in increased P sorption in low PSD soils. We hypothesize that these differences in soils of different PSD are linked to the different binding mechanisms of P depending on the saturation of binding sites. In our poster presentation, results of competitive P desorption, and amounts of organic compounds actually sorbed based on stable isotope labeling will be presented.

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Quantification of organic phosphorus mineralization in soils using a dual isotope

(32P and 18Op) method

Charlotte Vermeiren1, Erik Smolders1 1Department of Earth and Environmental Sciences, KU Leuven; Kasteelpark Arenberg 20, 3001

Leuven, Belgium.

Keywords: Organic phosphorus mineralization, oxygen-18 in phosphate, isotope

dilution.

Phosphorus (P) dynamics in arable soils are generally believed to be dominated by

reactions of inorganic P. Nevertheless, also organic P can have a substantial

contribution to fulfil the P needs of crops through mineralization processes.

However, to date, there is no accurate technique available to quantify this

contribution. This is due to the fact that measurement of organic P mineralization in

soils is particularly complex because of the large size of the inorganic P fraction and

the strong sorbing character of phosphate (PO4). The latter results in the immediate

removal of most of the freshly mineralized P from the soil solution, which makes it

difficult to measure the accumulation of soluble or extractable inorganic P. This

problem can be overcome by using isotope dilution techniques.

The goal of this project was to develop a method to quantify the mineralization of

organic P by using a combination of two isotopes: the radio-isotope 32P and the

stable 18O in phosphate (18Op). The proposed method is based on the concept that

these two isotopes behave identically in abiotic reactions, such as sorption

processes, but have a different fate in biotic reactions, such as immobilization and

mineralization. This is due to the fact that during mineralization of organic P, an

oxygen atom is exchanged between PO4 and surrounding water, resulting in an

Figure 2: Expected course of 32P and 18Op in soil solution over time. In abiotic conditions, both isotopes behave identically. Under biotic conditions, however, the delta-value of 18Op will undergo an additional dilution compared to the specific activity (SA) of 32P due to oxygen exchange with surrounding water.

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additional “dilution” of this isotope compared to 32P (Fig. 1). From this additional

dilution, the gross and net mineralization of organic P can be quantified through

conceptual modeling of the soil P dynamics.

To develop the method, an incubation experiment was performed with double

labeling of the soil. A Flemish arable soil was subjected to a full factorial design, with

factors being sterilization of the soil and amendment with glutamate to stimulate

microbial activity. In all treatments, the soil was spiked with 32P- and 18O-labeled PO4

and incubated for 50 days. At several points in time, the remaining fractions of both

isotopes as well as 31P were determined in an AEM-extract of the soil. By comparing

the dilution in the sterilized and the non-sterilized soils, the effect of biotic reactions

on the isotope dilution is currently being investigated and modeled. This technique

will yield a crucial piece of missing information in our knowledge about phosphorus

in the environment.

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The effect of dissolved oxygen and sediment iron on phosphate fluxes in lowland streams

Toon van Dael1

1Soil and water management, KU Leuven, Kasteelpark Arenberg 20, 3000 Leuven, Belgium

Keywords: Phosphate flux, sediment Flanders is known to have very high phosphate (PO4) concentrations in its surface water, with on average 0.52 mg P/l. Certain regions are characterised by very high peaks during the summer months, explaining the high average values. Smolders et al. (2017) suggest that these peaks are linked to reductive dissolution of iron(Fe)(oxy)hydroxides, Which are the most abundant P sorbent in sediments. There is, however, no proven causality for this link under field conditions. In this study short term additions of monoammonium phosphate (MAP) (NH4H2PO4) and bromide (Br) as an inert tracer were used to quantify P fluxes form or towards the sediment. The additions were executed in 4 streams with contrasting sediment Fe:P ratio and were repeated under low and high dissolved oxygen (DO) conditions. Under high oxygen conditions, all streams showed net retention of P of up to 25% of the added amount. When DO was sufficiently low (<5 mg O2/l) there was no net retention in the streams where the sediment Fe:P ratio was below 8 mol/mol. There was also an increase of dissolved Fe, which points to reduction of sediment iron. P Retention still occurred when the Fe:P ratio was sufficiently high. These results show that iron reduction can indeed induce P release from the sediment and explain summerly phosphate peaks in Flanders. References - Smolders E, Baetens E, Verbeeck M, et al (2017) Internal Loading and Redox Cycling of Sediment Iron Explain Reactive Phosphorus Concentrations in Lowland Rivers. Environ Sci Technol 51:2584–2592.

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Inositol pyrophosphates control eukaryotic phosphate homeostasis by binding

to SPX sensor domains

Michael Hothorn

Structural Plant Biology Laboratory, Department of Botany and Plant Biology, University of

Geneva, Switzerland

Keywords:Phosphate sensing, SPX domain, inositol pyrophosphate

Very different proteins involved in eukaryotic phosphate uptake, transport, storage,

metabolism and signaling harbor conserved SPX domains. We have previously shown

that these SPX domains act as cellular sensors for inositol pyrophosphate (PP-InsP)

signaling molecules, whose cellular concentrations are known to change when

external phosphate becomes limiting (Wild et al., 2016). Using the plant Arabidopsis

thaliana as a model system, I will present physiological, genetic, quantitative

biochemical and crystallographic data which together reveal a molecular link

between PP-InsP metabolism and phosphate homeostasis / starvation responses.

Collectively these findings suggest that eukaryotic phosphate sensing occurs at the

level of PP-InsP synthesis and breakdown.

References

- Wild et al. (2016) Control of eukaryotic phosphate homeostasis by inositol

pyrophosphate sensor domains. Science: 352(6288):986-990.

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Breeding phosphorus efficient rice: From classical breeding to genomic

prediction

Matthias Wissuwa1, Juan Pariasca-Tanaka1, James DM King1, Katsuhiko Kondo1, Sarah

Mandaharisoa2, Nicole Ranaivo2, Mbolatantely Rakotondramanana2 1Japan International Research Center for Agricultural Sciences (JIRCAS), Crop Production and

Environment Division, Ohwashi, Tsukuba, Ibaraki, Japan 2FOFIFA (Centre National de Recherche Appliquee au Developpement Rural), Antananarivo 101,

Madagascar.

Keywords: Phosphorus acquisition, P utilization efficiency, P deficiency, root traits,

traditional varieties.

Modern rice breeding has produced varieties with yield potentials in excess of 8 t ha-

1, yet regional averages frequently do not even reach half of this potential yield. This

yield gap is largely caused by biotic and abiotic stresses such as drought or low soil

fertility. Madagascar is Africa's second largest rice producer with national average

yields of 2.8 t ha-1 and phosphorus (P) deficiency is considered the main yield-limiting

factor as smallholder farmers typically do not apply fertilizers. Under such conditions

modern high yielding varieties are often out-performed by traditional varieties and

the question to be explored in this paper is how to best harness adaptive traits and

underlying genetic factors of these traditional varieties in crop improvement.

Options range from simply utilizing them as donors in traditional selection schemes,

to trait-centered approaches based on our understanding of key physiological and/or

morphological adaptations to P deficiency, to selection based on genomic models

that are built on high-throughput marker or genome sequence data. In our breeding

work in Madagascar we follow all three approaches and while touching upon

traditional selection and genomic prediction, the main focus will be on trait-based

approaches. P uptake in rice has been linked to the Pup1 locus that enhances root

development under P deficiency, however, additional root traits related to root fine

structure are now being explored genetically and through modeling of P uptake

processes in contrasting genotypes. An additional target trait is improved internal P

utilization efficiency (PUE). Genotypic variation for PUE has been identified in rice

and crosses with high-PUE donors have been made, however, selection for this trait

is difficult as rapid high-throughput screening methods are not available. The

development of molecular markers closely linked to superior PUE is therefore a

priority research target in order to achieve the goal of combining efficient P

acquisition with improved internal P utilization efficiency (PUE) in new rice varieties

that would benefit resource-poor farmers.

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ORAL PRESENTATIONS Tuesday 11 September

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Phosphate-Metal Interactions Govern Root Development

Steffen Abel, C. Naumann, J. Müller, M. Heisters, T. Toev, C. Alfs, J. Ziegler, R. Chutia

Department of Molecular Signal Processing, Leibniz Institute of Plant Biochemistry,

Weinberg 3, 06120 Halle (Saale), Germany

Keywords: Phosphate sensing, metals, root growth

Phosphate (Pi) is a major node in bioenergetics and therefore a genuinely limiting

factor of plant productivity. To cope with widespread Pi limitation, plants activate a

set of coordinated adaptive responses that reprioritize internal (systemic) Pi

allocation and maximize external (local) Pi acquisition by dynamic adjustment of

metabolism and root development, respectively. In search of Pi, root growth must

negotiate abundant soil metals and their associated toxicities, foremost Al and Fe,

which severely restrict Pi bioavailability by forming insoluble Pi complexes. Work in

the model plant Arabidopsis thaliana revealed antagonistic interactions between Pi

and its associated metallic cations in monitoring external Pi availability by root tips.

We showed that two functionally interacting genes, PDR2 and LPR1, mediate Fe-

dependent local Pi sensing. PDR2, the single orphan P5-type ATPase ATP5A,

functions in the endoplasmic reticulum and controls cell wall-targeted LPR1

ferroxidase activity, which causes rapid (<20h) cell type-specific Fe accumulation

upon Pi deprivation. Antagonistic Pi-Fe interactions in cell walls trigger ROS

production and callose deposition in root tips, followed by inhibition of cell-to-cell

communication and root meristem activity. Loss of PDR2 also alters pectin

deposition, expression of cell wall modifying enzymes, and root exudation profiles,

which support a function of PDR2 in secretory processes and cell wall remodeling.

Interestingly, a pdr2 suppressor screen for rescue of hypersensitive root growth

inhibition on low Pi identified new lpr1 mutations and two additional genes, ALMT1

and STOP1, which interact to activate malate exudation into the rhizosphere and cell

wall space upon Pi limitation. ALMT1 is a direct target gene of the STOP1

transcription factor and encodes an Al-activated malate efflux channel of key

importance for Al detoxification, which thus points to intricate Pi-Al interactions in

Pi sensing. Chemical (malate) complementation of the long almt1 root phenotype on

low Pi medium revealed a critical role of metal (Fe, Al) chelation in Pi sensing. To

better understand Pi-metal interactions in the local root response to Pi deprivation,

we systematically studied the synergistic effects of Fe and Al in Pi limited medium,

conducted detailed structure-function studies on the LPR1 ferroxidase, and

investigated the regulation and impact of Pi-dependent malate synthesis and

exudation. We will present and discuss our results.

References

- Abel S (2017) Phosphate scouting by root tips. Curr Opn Plant Biol 39:168-177

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- Hoehenwarter W. et al. (2016) Comparative expression profiling reveals a role of the root

apoplast in local phosphate response. BMC Plant Biol 16:106

- Ziegler J. et al. (2016) Non-targeted profiling of semi-polar metabolites in Arabidopsis root

exudates uncovers a role for coumarin secretion and lignification during the local response to

phosphate limitation. J Exp Bot 67:1421-1432

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Genetically controlled detection of endogenous inorganic polyphosphate (poly

P) pools in plants

Jinsheng Zhu1, Sylvain Loubery1, Michael Hothorn1 1Department of Botany and Plant Biology, University of Geneva, 30 Quai E. Ansermet, 1211

Geneva, Switzerland.

Keywords: inorganic polyphosphate; polyphosphate kinase; Arabidopsis thaliana;

fluorescent protein,

Inorganic polyphosphate (polyP), linear chains of phosphate residues linked by

energy rich phosphoanhydride bonds, forms an important phosphate and energy

story in many pro- and eukaryotic organisms. PolyPs are present in green algae but

the metabolism and physiological roles for polyP in higher plants are poorly

understood, partly due to the fact that specific detection of polyP pools in eukaryotic

cells and tissues is difficult. To develop specific detection protocols for polyP in

plants, we generated Arabidopsis lines which stably over-express a heterologous E.

coli polyphosphate kinase 1 (EcPPK1) and its catalytically variant EcPPK1H435A; H592A,

with a C-terminal mCitrine tag. Over-expression of EcPPK1, but not EcPPK1H435A;

H592A, caused severe growth phenotypes in Arabidopsis and led to an accumulation

of poly P in different organs (Fig 1).

Fig.1. The growth phenotype of plants over-expressing EcPPK1 and EcPPK1H435A; H592A.

Specific staining of these induced PolyP pools was achieved by staining with JC-D7, a

recently reported fluorescent probe which binds synthetic polyP in vitro and

endogenous poly P in mammalian cells (Angelova et al., 2014). PolyPs could also be

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labeled in planta by expression of a specific polyP protein binding domain, generated

from the C-terminal domain of a E. coli exopolyphosphatase (EcPPXc) (Werner et al.,

2007).

In agreement with our light microscopy experiments, polyphosphate granules could

also be visualized at the molecular level by Transmission Electron Microscopy (TEM).

Using the polyP staining protocols derived from these experiments, we screened for

polyP pools in many different mono- and dicots and in various organs and tissues.

References:

- Angelova PR, Agrawalla BK, Elustondo PA, et al (2014) In Situ Investigation of

Mammalian Inorganic Polyphosphate Localization Using Novel Selective Fluorescent Probes JC-

D7 and JC-D8. ACS Chem Biol 9:2101–2110.

- Werner TP, Amrhein N, Freimoser FM (2007) Inorganic polyphosphate occurs in the

cell wall of Chlamydomonas reinhardtii and accumulates during cytokinesis. BMC Plant Biol 7:51.

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The green alga Chlorella vulgaris has a high capacity of phosphorus

accumulation, mainly in the form of polyphosphate

Andres Sadowsky1, Dipali Singh 2, Š. Moudříková3, B. Ackermann4, P. Mojzeš3, O. Ebenhöh2, L.

Nedbal4, T. Mettler-Altmann1 1CEPLAS (Cluster of Excellence on Plant Sciences) & Institute of Plant Biochemistry, Heinrich

Heine University Germany 2Institute of Quantitative and Theoretical Biology, Heinrich Heine

University, Germany. 3Institute of Bio- and Geosciences / Plant Sciences and Agrosphere,

Germany. 4Institute of Physics, Faculty of Mathematics and Physics, Charles University, Czech R.

Keywords: Polyphosphate, Chlorella vulgaris, fertilizer

Phosphorus (P) is a major plant nutrient that is essential for modern agriculture.

Currently, global food and feed production, and therefore food security, depends on

P extracted from finite phosphate rock reserves exploited in a small number of

countries. This means that the majority of P used in agriculture today is of non-

renewable character. The International Fertilizer Industry Association predicts fossil

P-need to continuously increase, while prices might increase with a potential

unsecured phosphate rock availability.The efficiency of P usage today barely reaches

20%, with the remaining 80% ending up in wastewater. The potential of microalgae

to accumulate large quantities of P from wastewater can be a way to direct this

resource back to crop plants. Algae can acquire and store P, and the P enriched algal

biomass can be used as fertilizer. We investigated the capacity to accumulate and

store P in the fast-growing green alga, Chlorella vulgaris. In green algae, similar to

other microorganism such as yeast, a large proportion of the cellular P is found as

polyphosphate (polyP). PolyP is a linear chain of inorganic phosphate containing up

to several hundred phosphate residues linked by energy rich phosphoanhydride

bonds and is ubiquitous in all kingdoms of life. We first established two methods for

polyP quantification, an enzymatic assay and a Raman approach. We then examined

the phosphate uptake of phosphate-starved algae exposed to high phosphate levels

as it was shown previously that phosphate per dry weight is particularly high during

this treatment. We could identify two phases. In the first phase, phosphate was

taken-up very quickly. This uptake was accompanied by a significant increase of the

polyphosphate (polyP) levels. At the end of this phase, the maximal amount of

phosphorus was found per cell. During the second phase, growth-related processes

kicked-in, the cells started to divide again and the previously accumulated polyP was

degraded again. We applied a mathematical model for estimate fluxes of P into polyP

and out of polyP into growth. Our findings show that polyP is not only a long-term

storage, as postulated earlier, but can also serve as a short-term buffer of phosphate

when phosphate is externally available but growth processes are inhibited. Finally,

the potential of applying such phosphate-rich algal biomass to crop as fertilizer will

be discussed.

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Phosphatase activity and phosphorus depletion in the rhizosphere of blue lupin

(Lupinus angustifolius) assessed with 2D imaging

Gustavo Boitt1, Christina Roschitz2Jakob Santner2, Walter Wenzel2, Niklas Lehto1, Leo Condron1 1Lincoln University, Department of Agriculture and Life Sciences, Lincoln 7647, New Zealand. 2University of Natural Resources and Life Sciences, Department of Forest- and Soil Sciences,

Department of Crop Sciences, Konrad-Lorenz-Strasse 24, 3430 Tulln, Austria.

Keywords: Rhizosphere, phosphatase activity, P depletion

The widespread phosphorus (P) deficiency in agricultural soils is reflected in a

dependency on external P fertilizer inputs. Agronomically, lupins are interesting due

to their ability to associate with nitrogen fixing bacteria and mobilize P from organic

and inorganic pools in soils. Plant and microbial P mobilization processes include

acidification and exudation of organic anions, as well as enzymes. Understanding the

functionality of phosphatase enzymes and how they are linked to the organic P

dynamics and bioavailability is paramount. Recently, innovative non-destructive 2D

imaging methods such as zymography and diffusive gradients in thin films (DGT) have

come up for assessing the distribution of phosphatase activity and labile solutes at

the root-soil interface. Here we demonstrate for the first time the combination of

these two powerful techniques to improve our comprehension of root-soil-

microbiota interactions in P mobilization. The objective was to study and locally

quantify the mechanisms of P mobilization and associated phosphatase activity in

the rhizosphere of blue lupin (Lupinus angustifolius) in two contrasting, P-limited

soils from New Zealand. Soil “A” had total C 9.1 g kg-1, organic P 42 mg kg-1, total P

100 mg kg-1; and soil “B” had total C 31 g kg-1, organic P 381 mg kg-1, total P 899 mg

kg-1. Plants were grown in rhizotrons in glasshouse conditions for 45 days. We used

a combination of 4-methylumbelliferylphosphate (4-MUP) based zymography for

phosphatase activity mapping, and DGT gels capable of simultaneously binding labile

P and cations to investigate P mobilization, depletion and co-solubilization of

elements associated with P. Exudation of phosphatases was evident in the

rhizosphere (~1-2 mm) of plants grown in both soils. Phosphatase activity increased

from the root tips to the root hair zone (Figure ii and v) suggesting a relationship

between the elongation of root hairs and production of phosphatases as a

mechanism for P acquisition. Phosphatase activity observed along root/between

roots were consistent to soil P depletion zones but differed in the 2 soils (Figure iii

and vi). Further analysis of elements such as Fe, Cu, Zn and Mn, as well as Ca and Al

in the rhizosphere of both soils will provide further insights into P mobilization

processes and plant-microbe interactions. This study is ongoing.

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Digital images of Lupinus angustifolius roots grown in soils A (i) and B (iv), and; respective

distribution of phosphatase activity (nKat mm-2) (ii and v), and phosphorus depletion zones (ng

cm-2) (iii and vi).

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Can Pseudomonas protegens CHA0 solubilize phosphorus otherwise

unavailable to plants? Insights from radioisotope studies

Gregor Meyer1,2, Monika Maurhofer3, Else K. Bünemann2, Emmanuel Frossard1, Paul Mäder2,

Astrid Oberson1 1Group of Plant Nutrition, Institute of Agricultural Sciences, ETH Zurich, Lindau, Switzerland.

2Research Institute of Organic Agriculture FiBL, Frick, Switzerland. 3Group of Plant Pathology, Institute of Integrative Biology, ETH Zurich, Zurich, Switzerland.

Keywords: Phosphorus solubilizing bacteria, 33P techniques, wheat

Inoculation of soils with phosphorus (P) solubilizing bacteria (PSB) is being proposed

as a means to enhance the availability to crops via mobilization of non-available soil

and fertilizer P. Solubilization of inorganic P compounds by bacterial strains such as

Pseudomonas protegens CHAO (de Werra et al. 2009) able to exude organic acids

has often been shown on agar plates and in liquid media. However, the effects of

inoculation on P availability to plants growing in soils are inconsistent and do not

allow separating between direct effects on P availability and indirect effects such as

improved plant health. This differentiation can be achieved by using P radioisotope

techniques. With 33P isotopic dilution, the plant available soil P pool is labelled with 33P and microbial mobilization of non-labeled inorganic and organic P is deduced

from increased dilution in the specific activity (33P/31P) in soil solution or in plant

shoot.

We applied this approach in a pot study with Lolium multiflorum inoculated with

Pseudomonas protegens CHA0 (Meyer et al. 2017). The slight increase in P uptake

following inoculation could not be assigned to P mobilization from soil or fertilizer,

since the specific activity of P taken up by ryegrass was unaffected by inoculation.

However, any P solubilization by the inoculant could have been masked by reduced

activity of soil endogenous microorganisms. Therefore, we did a plant growth and

plant-free soil incubation experiment using 33P labeled synthetic hydroxyapatite

(Ca33P) in sterilized soil, again with the gluconic acid producing P. protegens CHA0

wild type and additionally included the no gluconic acid producing CHA1198 mutant

strain.

The 33P tracer approach and comparison with the mutant revealed that CHA0

solubilized no Ca33P, despite maintenance of high population sizes in rhizoplane and

in the sterilized soil. Also with glucose additions relevant to rhizosphere

concentrations, no solubilization was detected, suggesting that glucose availability

still limited production of gluconic acid, or that produced gluconic acid was not

effective in the calcareous soil. Instead, mechanisms related to overall microbial

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activity seemed to explain inorganic P solubilization and increased plant P uptake in

both inoculated treatments.

Thus, isotope techniques and an appropriate bacterial control should be used to

reveal the mechanisms involved in increased plant growth and/or changes in plant

available P following inoculation with PSB.

References

- de Werra P, Pechy-Tarr M, Keel C, Maurhofer M (2009) Role of gluconic acid

production in the regulation of biocontrol traits of Pseudomonas fluorescens CHA0.

Appl Environ Microbiol 75: 4162-4174.

- Meyer G, Bünemann EK, Frossard E, Maurhofer M, Mäder P, Oberson A

(2017) Gross phosphorus fluxes in a calcareous soil inoculated with Pseudomonas

protegens CHA0 revealed by 33P isotopic dilution. Soil Biol Biochem 104: 81-94.

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Acid phosphatase activity in hyphal exudate of arbuscular mycorrhizal fungus

Rhizophagus clarus under low P condition

T. Sato1, S. Hachiya1, N. Inamura1, T. Ezawa2, W. Cheng1, Keitaro Tawaraya1 1Faculty of Agriculture Yamagata University, Tsuruoka 997-8555 Japan, 2Graduate School of

Agriculture, Hokkaido University, Sapporo 060-8589 Japan

Keywords: acid phosphatase, arbuscular mycorrhizal fungus, hyphal exudate

Arbuscular mycorrhizal (AM) fungi enhance uptake of available phosphorus (P) from

soil. The mechanism underlying this P uptake enhanced by AM fungi is the increase

in surface area for absorption of available P. Organic P accounts for 30-80 % of total

soil P. Some plants hydrolyze organic P by secreting acid phosphatase (ACP) from

roots, especially under low-P conditions. Little is known about utilization of

unavailable P by AM fungi. We investigated whether extraradical hyphae of AM fungi

exude ACP and whether ACP activity responds to phosphorus condition. Sterilized

Andosol was packed in pots that were separated into the mycorrhizal and hyphal

compartments with a nylon net of 30 μm pore size. Seeds of Allium fistulosum L.

were inoculated or uninoculated with the AM fungus Rhizophagus clarus in P

fertilized soil (0 (P0) and 0.5 (P5) g P2O5 g-1). Soil solution including hyphal exudate

was collected by using mullite ceramic tubes. Hyphal extracts were extracted from

extraradical hyphae grown on sand culture and in vitro monoxenic culture,

respectively. Root exudate of A. fistulosum was collected from hydroponic culture.

The soil solution, hyphal extracts, root extract and root exudates were subjected to

sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis. L. usitatissimum

inoculated with R. clarus was grown on solid minimal media with three (3 and 30

µM) P levels. The extraradical hyphae and hyphal exudates were collected and

subjected to analysis of ACP activity by using p-nitrophenylphosphate. AM

colonization, shoot dry weight, and shoot P concentration were also measured. P

concentration, P content and dry weight of shoot were higher in the inoculated

treatment than in the uninoculated treatment. Activity staining of the gel revealed

that ACP activity at 187 kDa was observed in the soil solution in the inoculation

treatment, and in the hyphal extract collected from sand culture and in vitro

monoxenic culture, but neither in the root exudate of non-mycorrhizal plant grown

in the hydroponic culture nor in the root extracts irrespective of mycorrhizal status.

ACP activity of extraradical hyphae and hyphal exudates were higher in 3 µM

treatment than 30 µM treatment. These results suggest that the fungus releases ACP

from extraradical hyphae into the hyphosphere and soil P status affect ACP activity.

References

Sato T, Ezawa T, Cheng WG, Tawaraya K (2015) Release of acid phosphatase from extraradical hyphae of

arbuscular mycorrhizal fungus Rhizophagus clarus. Soil Science and Plant Nutrition 61: 269-274.

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Ectomycorrhizal utilization of different phosphorus sources in a glacier

forefront in the Italian Alps

Michele D'Amico1, Juan Pablo Almeida2, Sonia Barbieri1, Fabio Castelli1, Elena Sgura1, Giulia

Sineo1, Maria Martin1, Eleonora Bonifacio1, Hakan Wallander2, Luisella Celi1 1DISAFA, Università degli Studi di Torino, Largo Braccini 2, Grugliasco (TO), Italy. 22Department of Biology, Lund University, Sölvegatan 35, 223 62 Lund, Sweden

Keywords: organic P, P-release mechanisms, electron donor compounds,

Serpentine, P-poor soils

In deglaciated surfaces, habitats characterized by different ages coexist over short

distances and their development is influenced by lithology. In particular, serpentinite

inhibits soil evolution and plant colonization because of insufficient phosphorus (P)

content, among many other stressful properties. Small quantities of gneiss in the till

can partly compensate the harsh conditions for biota and enhance plant colonization

and pedogenesis. In nutrient poor environments, ectomycorrhizal fungi (EMF),

symbiotically associated with trees, play a key role exploring the soil for P beyond

the rhizosphere, and producing enzymes for P release from organic P compounds.

However, several studies show a limited enzymatic hydrolysis of inositol phoshates

when the latter interact with the mineral phase, although this has never been

explored for EMF.

In this study we followed the role of EMF on P plant availability in two proglacial soil

chronosequences in the Alps, characterized by pure serpentinite till and serpentinite

mixed with 10% of gneiss, respectively. The dominant tree in the area is European

Larch, which forms associations with EMF. The tree cover is sparse on 50-190 year-

old soils, and it increases to dense stands in later successional stages (1000-3000

year-old soils). Sites at 5, 70, 190 and 3000 years of age were chosen in each

chronosequence and the uptake of inorganic and organic P forms by EMF was

studied using specific mesh bags for fungal hyphae entry but not roots. The mesh

bags were filled with inorganic phosphate (Pi) or myo-inositolhexaphosphate (InsP6)

adsorbed onto goethite and associated to quartz sand. These bags were incubated

over 3 and 13 months at the organic/mineral horizon interface. After harvesting,

EMF colonization via ergosterol analysis and the amount of P and Fe removed from

mesh bags were measured.

Ergosterol increased along the two chronosequences with slightly higher values on

serpentinite and in the Pi containing bags. On pure serpentinite, up to 65% of Pi was

removed from mesh bags after 13 months, only partly accompanied by a parallel

release of Fe. The amount of InsP6 released was instead less than 45% and almost

completely removed contemporary to Fe. This may suggest that EMF can produce

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organic acids as competitors for the same sorption sites and electron donor

compounds for goethite reductive dissolution, suggesting the combination of

different strategies for taking up Pi, but also InsP6, in such limited environments.

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Combined phosphorus and water management options towards

sustainable intensification of rice production in P-deficient lowlands of

sub-Saharan Africa.

Pieterjan De Bauw1, Elke Vandamme2, Kalimuthu Senthilkumar³, Allen Lupembe², Erik

Smolders1, Roel Merckx1

1 Katholieke Universiteit Leuven, Dept. of Earth and Environmental Sciences, Belgium. 2 Africa

Rice Center (AfricaRice), Dar es Salaam, Tanzania. 3Africa Rice Center (AfricaRice), Antananarivo, Madagascar

Key words: Root Plasticity, Water Saving Technologies, P Uptake Efficienc

In large parts of sub-Saharan Africa (SSA), rice (Oryza spp.) serves as an important staple crop. Population growth and urbanization drastically increase rice consumption. Rice production should concomitantly increase to reduce dependence on rice imports, which endangers food security in many African countries. Drought and low phosphorus (P) availability are two major abiotic constraints for rice production in SSA. With increasing prevalence of water scarcity and the decline of phosphate reserves, it is urgent to develop sustainable solutions countering these limitations. Both water and P availability can influence root development in several ways. Understanding root plasticity under combinations of P and water availability is important in efforts towards enhancing resilience to both stresses. Additionally, research towards the optimization of management practices in P and/or drought prone environments is needed to identify opportunities for improvement of resource use efficiencies and rice production. A first part of this work examined how rice roots respond to several combinations of P and water availability. It is shown that water availability has a dominant modifying role on root architecture which in turn affects the P uptake efficiency. This root plasticity suggests possible benefits of reduced water application in P deficient environments.In a second part, several combinations of water saving technologies (i.e. alternate wetting and drying and aerobic rice) and specific P fertilization techniques (i.e. micro-dose placements and broadcasting) were tested in P-deficient lowlands. Root development, yields, and fertilizer and water use efficiency were analyzed in order to identify best bet management options towards sustainable intensification of drought-prone and P-deficient rice growing lowlands. Promising effects of P micro-dosing were observed under each water management scenario, but attention should be paid to counteract further P mining of the depleted soils. Root development was predominantly affected by water management as rooting depth and lateral thickness increased and nodal thickness decreased under water saving technologies. Reduced water application not only increases water productivity but also enhances growth and yield when P is limiting. We conclude that strategic combinations of P and water management, capitalizing on the root plasticity here demonstrated, can contribute to the intensification of rice production in P deficient lowlands.

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Inadvertent selection for root proliferation in response to P in Australian wheat

breeding programs due to rainfall patterns

Chris Guppy1, Sheikh Fazle Rabbi2, Iain Young2, Richard Flavel1 1Agronomy and Soil Science, The University of New England, Armidale, Australia. 2Centre for

Carbon, Water and Food, The University of Sydney, Sydney, Australia.

Keywords: Root proliferation, fertiliser banding, wheat

As P is depleted from Australian cropping soils, producers band P fertiliser applications to reduce yield loss. Little is known concerning the root proliferation response of wheat varieties commonly grown in Australia and their ability to exploit patches enriched with P. Twenty wheat varieties (10 southern Australian bred; 10 northern Australian bred) were screened for root plasticity in response to elevated solution P concentration using the method described by Rabbi et al. (2017). Despite no observed difference in root plasticity within northern bred wheat lines, southern bred wheat lines exhibited 4-fold variation in root plasticity (Figure 1a), but were generally far less responsive to P enriched patches than northern lines (Figure 1b). We propose that winter dominant rainfall patterns in southern Australia decreased root adaptation to patches of enriched P as surface soil P concentrations are less constrained during the growing season. However northern wheat production is reliant on stored soil moisture and may have inadvertently selected for root systems rapidly able to exploit P enriched soil during brief windows when the soil surface is moist.

Figure 1: Plasticity index of 10 southern and 10 northern (green box) Australian wheat lines (a); and cluster analysis ranking relative plasticity of root systems (b); when encountering patches enriched with P (c).

References: Rabbi S, Guppy C, Tighe M, Flavel R, Young I (2017). Root architectural response of

wheat (Triticum aestivum L.) cultivars to localised P application are phenotypically similar.

Journal of Plant Nutrition and Soil Science 180:169-177.

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Temporal patterns of nutrient availability: the importance of tropical

seasonality on bioavailability of phosphorus in the Central Amazon

Karst J. Schaap1, 2, L. Fuchslueger, O. Valverde-Barrantes, E. Oblitas, F. Hofhansl, K. Fleischer, S.

Garcia, A. Grandis, A.C de Araújo, D. Lapola, R. Norby, I. Hartley, M. Hoosbeek, C. A. Quesada

and Amazon FACE team. 1Biogeochemistry Laboratory, INPA (National Institute of Amazonian Research), Av. André

Araújo, 2936, Aleixo, Manaus, AM, Brazil. 2Dpt. of Soil Quality, Wageningen University, PO Box

47, Wageningen, The Netherlands

Keywords: Tropical forest, P availability

The Amazon forest is the world’s largest tropical forest, and largely grows on highly

weathered soils with low phosphorus (P). It is generally hypothesized that P limits

productivity in this system, but it is complex to determine the limits this poses on the

system and through what process. The knowledge of the functioning of the P-cycle

in the tropics is limited, especially when considering that P has different forms with

their own availability in the soil. P availability strongly depends on organic matter

recycling, which may follow seasonal fluctuations. The aim of this work was to

explore seasonal patterns and drivers of tropical soil P cycling. During a full year in

the Central Amazon, soils were collected and analyzed with a special emphasis on P

fractions (Hedley fractionation). Moreover, microbial biomass and activity (soil

extracellular enzymes), as well as plant leaf litter input and root production were

determined. Litterfall inputs peaked towards the end of the dry season and were

correlated with phosphatase activity. Simultaneously, easily available P (Olsen-P)

increased. Moreover, our results indicate a tight coupling of inorganic N and

available P cycling. Soil biochemical changes are aligned with the seasonal pattern of

P-availability and a gradual effect of rainfall on the P-availability was found.

Discussion: The coupling of biochemical properties of soils with the availability of P

indicates the complexity and co-dependencies of nutrients the ecosystem. This

seasonality is driven by supply of organic matter (litterfall) and plant uptake, which

are both driven by precipitation patterns. However, while P is the considered the

limiting nutrient, on a smaller scale other nutrients might have influence as well.

Seasonality of soil properties can give us insight in how the ecosystem dynamics

overcome this limitation. This study provides insight in how tropical forests can

flourish on relatively poor soils. Ultimately, this insight in nutrient cycling is crucial

to address how changes in one cycle (i.e. carbon, nitrogen, phosphorus) may be

amplified or alleviated when considering linkages to another cycle. In conclusion, soil

phosphorus availability varies throughout the year with availability increasing after

the dry season. This seasonality is important when considering the limitations of a

forest and the future changes; nutrient cycles have interdependencies that might

not be constant.

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Rapid microbial phosphorus (P) turnover under drying and rewetting

governs P availability in grassland soil as quantified by 33P isotopic

dilution.

Hao Chen1, Klaus A. Jarosch2, Éva Mészáros3, Emmanuel Frossard3, Xiaorong Zhao1, Astrid

Oberson3 1Key Laboratory of Arable Land Conservation (North China), Ministry of Agriculture, Key

Laboratory of Plant-Soil Interactions, Ministry of Education, College of Resources and Environmental Sciences, China Agricultural University, 2Institute of Geography, University of

Bern, Hallerstrasse 12, 3012 Bern, Switzerland,3Institute of Agricultural Sciences, Swiss Federal Institute of Technology Zurich (ETH), Eschikon 33, CH-8315 Lindau, Switzerland

Keywords: Drying-rewetting, microbial P turnover

Drying and rewetting (DRW) cycles are a common phenomenon in semiarid

grassland soils and can thereby influence soil nutrient availability. The soil microbial

biomass can be strongly affected by DRW, yet, the effects of DRW on microbial

bound P are little known. In particular, microorganisms may act both as a source or

as a sink of P during DRW, via P release at die-off of microbial biomass, and

immobilization of P by growing biomass due to carbon pules from dead

microorganisms. We thus aimed to determine and quantify the effect of DRW on

microbial P cycling on a semiarid grassland topsoil from northern China that regularly

experiences DRW cycles. For that, pre-incubated soil was labelled with carrier free 33P-orthophosphoric acid. The soil was then either incubated at constant soil

moisture or exposed to three DRW cycles, where one cycle consisted of a 2-day

drying phase, a 3-day dryness phase and a 4-day moist phase after rapid rewetting.

For both treatments, water extractable and microbial (i.e. fumigation labile) 31P

(orthophosphate) and 33P, and soil respiration rates were determined in 2 to 8-day

intervals. At the first DRW cycle, microbial P decreased by half during soil drying, with

a concomitant increase in water extractable P. Similar observations were made in

the second and third DRW cycle, yet, with less pronounced effects. Soil respiration

rates increased during all of the three drying phases, but respiration rates were

almost nil during phases of dryness. In treatment with constant soil moisture, water

extractable P and microbial P remained rather constant. Microbial P turnover was

derived from changes in specific activity (SA, i.e. the fraction of total applied 33P

isotopic tracer over 31P) in the microbial P pool. A strong decrease in microbial SA

during the first drying and dryness phase signaled a change in the isotopic

composition of the microbial bound P. This is either explained by the quicker die-off

of microorganisms that earlier took up more 33P isotopic tracer (higher initial growth

rates, but also more susceptible during drying), compared to slower growing

microorganisms. Alternatively, microorganisms withstanding the drying phase could

have taken up mineralized non-labelled organic P, as indicated by increased soil

respiration rates during drying phases, causing the decrease in microbial

SA.Microbial P turnover was thus strongly affected by DRW events, but their effects

appear to diminish with close repetition of the DRW cycles.

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Testing for resource partitioning of soil phosphorus in mixtures of crop species Chunjie Li1, 2, Thomas W. Kuyper2, Wopke van der Werf3, Junling Zhang1, Haigang Li1, Fusuo

Zhang1, Ellis Hoffland2 1 Centre for Resources, Environment and Food Security (CREFS), China Agricultural University,

Beijing, 100193, China 2 Wageningen University, Soil Biology Group, P.O. Box 47, 6700 AA Wageningen, The

Netherlands 3Wageningen University, Centre for Crop Systems Analysis, P.O. Box 430, 6700 AK Wageningen,

The Netherlands

Keywords: Phosphorus, complementarity

Plants have different rhizosphere-related strategies to mobilize various sparingly

soluble P sources in the soil, such as exudation of phosphatase, carboxylates and

protons. This difference could lead to enhanced P use efficiency by intercrops:

combinations of two crop species grown in the same field. We developed and

implemented a test for this hypothesis. Two experiments were conducted with

quartz sands in pots. In Experiment 1, the ability of twelve crop species to acquire P

from sparingly soluble sources (CaP, PhyP and FeP (50 mg P/kg)) was tested. We

demonstrated that millet and chickpea could mobilize P from CaP and PhyP,

respectively. Wheat and maize had similar abilities to acquire these P sources. So we

expected millet/chickpea mixture would take up more P from mixed CaP/PhyP than

from the single P sources, but the wheat/maize mixture would not. We tested this in

Experiment 2 where monocultures and mixtures of millet/chickpea and wheat/maize

were grown on mixed CaP/PhyP or single P sources. The observed P uptake from

mixed CaP/PhyP by millet/chickpea mixture was higher than the expected from

single P sources, which suggests complementary P uptake by millet/chickpea

mixture. Contrary to our hypothesis, wheat/maize mixtures took up 1.2-fold more P

from mixed P sources than from single P sources. Similarly, in Experiment 1, cabbage

and faba bean could effectively mobilize FeP and PhyP, respectively, whereas wheat

and maize had similar capacities to mobilize these two P sources. So the

cabbage/faba bean mixture was hypothesized to take up more P from the mixed

FeP/PhyP compared to their expected P uptake from single P sources, but the

wheat/maize mixture was not. We found that the cabbage/faba bean mixture took

up less P than expected based on P uptake from single P sources. Consistent with our

expectation, the results on the wheat/maize mixture did not indicate any

complementarity in P uptake from mixed FeP/PhyP. Our hypothesis that

combinations of plant species with different abilities to access sparingly soluble P

forms would take up more P from mixed P sources than expected, was confirmed in

only two of the four plant species/P sources combinations we tested. Because of

complicating factors such as unstable P acquisition traits and competitive inequality

between species, conditions under which the P resource partitioning hypothesis can

be tested are limited. This complicates designing for complementarity in soil P pools

by intercrops.

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Warming and biocrusts alter soil phosphorus fractions in two semi-

arid ecosystems

L. García-Velázquez1, 2, A. Gallardo2 & FT. Maestre1 1Departamento de Biología y Geología, Física y Química Inorgánica, Universidad Rey Juan

Carlos, C/Tulipán s/n, Móstoles 28933, Spain. 2Departamento de Sistemas Físicos, Químicos y

Naturales, Universidad Pablo de Olavide, Carretera de Utrera km. 1, Sevilla 41013, Spain

Keywords: P fractionation, global warming, biological soil crust

Increases in aridity due to global warming are expected to increase the extent of

drylands worldwide. Such aridification of current climate can have important effects

on biogeochemical cycles, inducing imbalances in soil utrients with subsequent

impacts on ecosystem services. In addition, the global increase of atmospheric

nitrogen (N) deposition can destabilize primary productivity in terrestrial

ecosystems, and P may become the most limiting nutrient in many ecosystems.

Several studies have shown that aridity and climate change influence N cycling in

drylands, but the impacts of climate change on soil inorganic and organic P fractions

in drylands remains poorly studied. We tested how a ~2.5 °C warming, a ~30% rainfall

reduction and the degree of biocrust development affected organic and inorganic P

fractions (resin-P, NaHCO3-P, NaOH-P, HCl-P and residual-P) in 10-yr and 8-yr field

experiments in Central and SE Spain. We performed a combination of classic

methods of soil P fractionation to determine proportions of organic and inorganic P.

Biocrusts had a great influence on soil P, increasing all P fractions. Soil warming

increased both inorganic (NaHCO3-P, NaOH-P and HCl-P) and organic (NaHCO3-P and

NaOH-P) P fractions. However, the rainfall exclusion experiment did not have any

effect on any of the P fractions evaluated. Our results suggested that global warming

is altering the biogeochemistry of soil P both directly and indirectly (via their impacts

on the development of biocrusts).

References

- Delgado-Baquerizo M, Maestre F. T, Gallardo A, Bowker M. A, Wallenstein M. D, Quero J.

L, ... & García-Palacios P (2013) Decoupling of soil nutrient cycles as a function of aridity in

global drylands. Nature 502:672.

- Fernández J. A, Niell F. X, Lucena J (1985) A rapid and sensitive automated determination

of phosphate in natural waters. Limnology and Oceanography 30:227-230.

- Maestre F. T, Escolar C, Guevara, M. L, Quero J. L, Lázaro R, Delgado‐Baquerizo M, ... &

Gallardo A (2013) Changes in biocrust cover drive carbon cycle responses to climate change

in drylands. Global change biology 19:3835-3847.

- Peñuelas J, Sardans J, Rivas‐ubach A & Janssens I. A (2012) The human‐induced imbalance

between C, N and P in Earth's life system. Global Change Biology 18:3-6.

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Large variation in readily available phosphorus in casts of eight earthworm species: a link to cast properties

Hannah M.J. Vos1, Gerwin F. Koopmans1, Lieke Beezemer1, Ron G.M. de Goede1, Tjisse Hiemstra1, Jan Willem van Groenigen1

1Department of Soil Quality, Wageningen University, P.O. BOX 47, Droevendaalsesteeg 4, 6700 AA, Wageningen, The Netherlands

Keywords : earthworms, P availability

Phosphorus (P) is often poorly available for uptake by plant roots because it strongly adsorbs to the soil mineral phase. According to recent research, earthworms can temporally and locally make adsorbed P available to plants. However, the pathways through which they do so are not fully understood, and it remains unclear to what extent this capacity varies among earthworm species. Here we study the effect of various earthworm species on readily available P in casts as well as other cast properties in a greenhouse pot experiment using a soil with a low P status. The earthworms belong to eight commonly occurring earthworm species in The Netherlands: two epigeic species (a mixture of the compost earthworms Dendrobaena veneta/Eisenia fetida; Lumbricus rubellus); four endogeic species (Allolobophora chlorotica, Aporrectodea caliginosa, Aporrectodea rosea, Octolasion lacteum); and two anecic species (Aporrectodea longa; Lumbricus terrestris). For all species, the pH in water extracts of earthworm cast (7.4-8.2) was significantly higher (p<0.001) than for the control soil (6.6) and it differed significantly (p=0.003) among earthworm species. Similarly, the Dissolved Organic Carbon (DOC) concentration in the same water extracts was an order of magnitude higher in earthworm cast compared to the control soil and varied among species (p<0.001). Although the size of the total pool of reversibly adsorbed P in earthworm cast was greater than in the control soil, no significant differences in the size of this pool were found among earthworm species. Differences among species were more pronounced for the readily available P pools extracted from casts, including P-Olsen and water-extractable ortho-P. Water-extractable ortho-P concentrations were dramatically higher in the cast of all species as compared to the control soil (0.9-6.8 vs 0.06 mg l-1; p=0.006). Highest ortho-P levels were measured in L. rubellus cast and the lowest for A. chlorotica. The observed positive correlation between the concentrations of DOC and ortho-P (r2=0.72) is in agreement with our previous modelling study1. The observed variation in all measured properties could not be explained by conventional ecological earthworm classifications. Our results suggest that the nature and magnitude of earthworm-induced P availability differs dramatically among earthworm species, indicating that the composition (and not simply the size) of the earthworm community is key to optimizing P availability to plants. References

Ros MBH, Hiemstra T, van Groenigen JW, Chareesri A, Koopmans GF (2017) Exploring the

pathways of earthworm-induced phosphorus availability. Geoderma 303: 99-109.

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Low molecular weight organic acids enhance the mobilization of soil cadmium and phosphorus

Yongzhuang Wang 1,2,3, Xiangying Peng 1,2,3, Xinying Zhang1,2,3 1Key Laboratory of Environment Change and Resources Use in Beibu Gulf, Guangxi Teachers

Education University, Ministry of Education, Nanning 530001, China; 2Guangxi Key Laboratory of Earth Surface Processes and Intelligent Simulation, Guangxi Teachers Education University, Nanning 530001, China;3College of Environment and Life Science, Guangxi Teachers Education

University, Nanning 530001, China

Keywords: Cd, mobilization, soil phosphorus Low molecular weight organic acids (LMWOAs) can mediate nutrients acquisition by altering soil chemical, physical and biological properties. Soil available cadmium (Cd) and phosphorus (P) are consequently affected by LMWOAs addition. But little is known about the effects of LMWOAs on the mobilization of Cd and P in soils with different Cd levels so far. The aim of this study was therefore to investigate the impacts of three common low molecular weight organic acids (citric acid, oxalic acid and malic acid) on the mobilization of cadmium (Cd) and P in soils with the status of low, middle and high Cd level. The Tessier sequential extraction method was also employed to explore the mechanisms of the interactions between phosphorus and Cd in soil. Surface layer (0-20cm) of the soil samples was collected from Longzhou Nature Reserve (22°8’-22°44’N, 106°33’-107°12’E). Oxalic acid, citric acid, malic acid was added at the rate of 0, 10, 20, 30, 40 and 50 mmol L-1 soil. Triplicate 30ml of oxalic, citric, or malic acid were added to 2 g soils in 50-ml centrifuge tubes. The suspensions were shaken for 24 h at 25±1°C. Inorganic P concentration of the extracts was determined by the malachite-green method using UV-721 Spectrophotometer at 610 nm. DTPA-extractable soil Cd was obtained by shaking for 2 hours at 25 °C. After that, the leachate was centrifuged, filtered for analysis of Cd by atomic absorption spectrometry (AAS). Soil extractable Cd and P contents were increased in the treatments with low molecular weight organic acids. Specifically, with the addition of 0-50 mmol L-1 LMWOAs, the level of extractable Cd and P was increased 5.2-67.9% and 4.1-43.3%, respectively. A comparison of impacts of LMWOAs types indicated that the amount of extractable Cd and P increased in the order of citric acid > malic acid > oxalic acid. The dissolvable Cd content was increased significantly with organic acids addition. The Cd carbonates bounded was increased with the oxalic acid addition. Fe-Mn oxidation Cd declined with the three organic acids addition. Conclusion: on the mobilization of soil Cd and P. Three organic acids addition can

significantly change Cd forms and enhance Cd absorption in plants

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Phosphate starvation and root branching in plants: two complex pathways with an early interaction

Hans Motte1, Hanne Crombez1, Wei Xuan2, Alexa De Knijf1, Boris Parizot1, Tom Beeckman1 1Department of Plant Biotechnology and Bioinformatics, Ghent University, and Center for Plant Systems Biology, VIB, Technologiepark 927, 9052 Ghent, Belgium. 2State Key Laboratory of Crop

Genetics and Germplasm Enhancement, Nanjing Agricultural University, Nanjing 210095, PR China

Keywords: Lateral root, Pre-branch site, Root cap The induction of root branching is a typical phosphate (Pi) starvation response that allows plants to forage for more Pi. Despite the increasing insight into the signaling pathways involved in root branching and Pi starvation responses, it is not clear how these two pathways interact. Our recently discovered root cap-dependent specification of pre-branch sites (Xuan et al., 2016) and the importance of the root cap for phosphate uptake and homeostasis (Kanno et al., 2016) points towards an early effect of Pi starvation on lateral root formation. To investigate this possibility, we performed a series of experiments using an Arabidopsis auxin response reporting DR5-luciferase line. Due to the sensitivity of luciferase and its fast activation and degradation, we were able to observe a highly specific spatiotemporal pattern of pre-branch sites in different Pi conditions. As such, we found that Pi starvation has an effect on the early auxin signaling and the number of pre-branch sites. Moreover, a meta-analysis using a modified VisuaLRTC (Parizot et al., 2010), including lateral root formation and phosphate starvation transcriptional and promotor-binding data, allowed us to pinpoint a number of molecular players important for this early interaction (Figure 1). Interestingly, among these genes, we retrieved AUXIN RESPONS FACTORs (ARFs) and auxin homeostasis enzymes functioning in the root cap and root meristem. Thus, our results unravel an unprecedented and early interaction between the phosphate starvation signaling and auxin-induced lateral root initiation. References - Parizot B, De Rybel B, & Beeckman T (2010) VisuaLRTC: a new view on lateral root initiation by combining specific transcriptome data sets. Plant Physiol. 153(1):34-40. - Kanno S, et al. (2016) A novel role for the root cap in phosphate uptake and homeostasis. eLife 5:e14577. - Xuan W, et al. (2016) Cyclic programmed cell death stimulates hormone signaling and root development in Arabidopsis. Science 351(6271):384-387.

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Figure 1: hypothetical model for early interaction between Pi starvation signaling and root branching inducing auxin signaling. Pi starvation signaling lead to higher auxin level at the root tip and induction of the TIR1 auxin receptor and ARF7/ARF19 transcription factors.

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Phosphorus-acquisition strategies of different crop species in soils amended with sewage sludge

C. Nobile1, D. Houben1, E. Michel1, N. Honvault1, H. Lambers2, E. Kandeler3, M-P. Faucon1 1AGHYLE, UniLaSalle, Beauvais, France, 2The University of Western Australia, Australia,

3University of Hohenheim, Stuttgart, Germany

Keywords: P mobilization, root system, sewage sludge Sewage sludge use is of major interest for sustainable phosphorus (P) fertilization. Optimal practices, particularly crop succession, can depend on the forms of P in the sludge applied, because they can impact P-acquisition strategies of crops. Here, we investigated how P acquisition by crops and mobilization traits are influenced by soil type and P fractions in sludge. We carried out a greenhouse pot experiment with two soils: a Calcosol and a Luvisol. Three types of sludge and a mineral fertilizer were applied at the same P rate; a control without fertilization was also included. Wheat, barley and rapeseed were sown separately and grown for three months. Crops traits involved in P acquisition and mobilization were measured. In the Luvisol, sludge application had no effect on available P and the P uptake did not differ among crops. By contrast, in the Calcosol, resin-P and Olsen-P concentrations increased with sludge application but these increases were not related to P fractions in sludge. The P uptake was positively correlated with available P concentrations in Calcosol, but differed strongly among crop species, with a faster uptake for rapeseed (Fig. 1). In Calcosol, P-acquisition traits and particularly specific root length (SRL) were

influenced by sludge application. Other plant traits identified to potentially increase P mobilization are the activity of acid phosphatase, root carboxylate exudation and colonization by AMF. P-acquisition increased with sludge application, but did not differ with P fractions in sludge. Root system

development influenced P acquisition

and mainly explained differences among crops. The different responses of P-acquisition traits to

sludge applications in crop species provides a strategy to the development of sustainable P fertilization by identifying the best application time of sludge in the rotation.

Figure 1: Relationship between P uptake by rapeseed,

wheat and barley, and resin-P concentration in Calcosol

amended with sewage sludge

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Phosphorus acquisition mechanisms of potato (Solanum tuberosum L.) Mareike Kavka1, Katrin Wacker1, Klaus J. Dehmer2, Ralf Uptmoor1

1Agronomy, University of Rostock, Justus-von-Liebig-Weg 6, 18059 Rostock, Germany. 2Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), Gross Luesewitz Potato

Collections, Parkweg 3a, 18190 Gross Luesewitz, Germany.

Keywords: P uptake, phosphatases, root architecture Potato is an important crop used for food and starch production. In comparison to other crops, potato has a low ability to take up phosphorus (P) from the soil and its fertilizer demand is accordingly high (Rosen et al. 2014). General strategies to enhance the P uptake from the soil include increasing root phosphatase activity to cleave phosphate from organic compounds and a restructuring of the root architecture for better use of unevenly distributed phosphorus reserves in the soil (Vance et al. 2003). The present study aims at the identification of potato genotypes with high P acquisition and at the elucidation of mechanisms regulating P acquisition. The P acquisition and P use efficiency of 30 potato genotypes grown in high and low P conditions were evaluated. Genotypes with contrasting P efficiencies were selected for a detailed study of mechanisms to enhance P uptake. Therefore, micro-RNA 399 (miR399), a key player in phosphorus signaling, and acid phosphatase gene expression, root and soil phosphatase activity and root architecture parameters were estimated. Additionally, selected genotypes were grown in a long-term field experiment and received manure or triple super phosphate as P fertilizers. Furthermore, they were cultivated on control plots, which have not been fertilized with P since 1998. Potato genotypes showed a high range of P acquisition and use efficiency. Mature miR399 expression as well as root associated and soil acid phosphatase activity were higher when plants propagated in vitro were grown in low P conditions. However, no differences were found between genotypes with contrasting phosphorus efficiencies. Root system size depended on both genotype and P level but was not correlated with P uptake under low P conditions. When propagated from tubers and grown in both pots and in the field, no clear P deficiency signals were found. We conclude from the present study that adaptation mechanisms of potato on the molecular, enzymatic and morphological level do not necessarily improve P uptake from deficient soils. Our results give hint that P mobilized from the mother tuber might be sufficient for plant nutrition during early growth stages. Older plants are able to acquire the amount of P needed for optimal growth even if the soil P status is highly deficient according to the German P fertilization recommendations. References - Rosen CJ, Kelling KA, Stark JC, Porter GA (2014) Optimizing Phosphorus Fertilizer

Management in Potato Production. Am J Potato Res 91:145–160. - Vance CP, Uhde-Stone C, Allan DL (2003) Phosphorus acquisition and use: critical adaptations by plants for securing a nonrenewable resource. New Phytol 157:423–447.

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Signal beyond nutrient – Fructose exuded by an arbuscular mycorrhizal fungus triggers phytate mineralization by a phosphate solubilizing bacterium

Lin Zhang1, Gu Feng1, Stéphane Declerck 2

1 College of Resources and Environmental Sciences, China Agricultural University, Beijing

100193, China. 2 Université catholique de Louvain, Earth and Life Institute, Applied microbiology, Mycology,

Croix du sud 2, bte L7.05.06, B-1348 Louvain-la-Neuve, Belgium

Keywords: Mycorrhizal pathway, organic phosphorus, hyphosphere interaction

Context: The extraradical hyphae of arbuscular mycorrhizal fungi (AMF) harbor and interact with a microbial community performing multiple functions. However, how the AMF-bacteria interaction influences the phosphorus (P) acquisition efficiency of the mycorrhizal pathway is unclear. Objective and methods: We investigated whether fructose, glucose and trehalose are present in the hyphal exudates of AMF Rhizophagus irregularis and if they are potential candidate signaling compounds to prime the processes related to metabolism of cell and phosphatase production in the phosphate solubilizing bacterium (PSB) Rahnella aquatilis under strict in vitro culture conditions. Results: We observed that fructose exuded by the AMF stimulated the expression of phosphatases genes in the bacterium as well as the rate of phosphatases release into the growth medium by regulating its protein secretory system. The phosphatase activity was subsequently increased, promoting the mineralization of organic phosphorus (i.e. phytate) into inorganic phosphorus, stimulating simultaneously the processes involved in phosphorus uptake by the AMF. Discussion and conclusion: Our results demonstrated for the first time that fructose not only is a carbon source, but also plays a role as a signal molecule triggering bacteria-mediated organic phosphorus mineralization processes. These results highlighted the molecular mechanisms by which the hyphal exudates play a role in maintaining the cooperation between AMF and bacteria.

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Figure 1: Schematic representation of the reciprocal rewards of carbon (C) and phosphorus (P) between the arbuscular mycorrhizal fungus (AMF) R. irregularis and the phosphate-solubilizing bacterium (PSB) R. aquatilis. ST, sugar transporter; fruT, fructose transporter; gluT, glucose transporter; PT, phosphate transporter; PSS, protein secretory system; Pase, phosphatase; Pi, inorganic P; Po, organic P.

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Highlighting phosphorus-acquisition strategies in intermediate crops, a functional approach

Honvault Nicolas1,2, Houben David1, Lambers Hans3, Cécile Nobile1, Stéphane Firmin1, Faucon

Michel-Pierre1

1AGHYLE Institut Polytechnique Unilasalle 19 Rue Pierre Waguet, 60000 Beauvais,France 2Vivescia 2 Rue Clément Ader, 51100 Reims, France

3School of Biological Sciences, University of Western Australia,35 Stirling Highway,Crawley WA 6009, Australia

Keywords: Intermediate crop, Phosphorus-acquisition strategies, Phosphorus availability, Plant functional traits

Phosphorus (P) is an important driver for the functioning and productivity of agroecosystems. In Europe, the intensive use of P fertilisers, which are mainly derived from mined phosphate rock, a finite and non-renewable resource, has led to an accumulation of P in soils. A major challenge of sustainable agriculture is now to develop cropping systems that increase P availability, while decreasing inputs of chemical fertilizer. One way to achieve such results is to include plants with high P mobilisation or acquisition potential in the cropping systems, i.e. in the rotation, intercrop, permanent cover crop and intermediate crop. Intermediate crops can improve P availability through root effects (phosphatases activity, carboxylate and proton release) or through the decomposition of their residues (release of P, change in soil pH). The influence of intermediate crop species on P dynamics and availability, however, depends on their multiple above and belowground functional traits, and their interactions in different soil types are only partly understood. A better understanding of the relationship between traits in crops could help ensuring enhanced ecological complementarily in multi-species systems, hence increasing P availability. The objective of this study was to examine the covariation of plant functional traits involved in P availability to identify the different P-acquisition strategies, in order to design the functional structure of intermediate crops in two types of soil (Retisol and Calcisol). We carried out a three-months greenhouse experiment with 14 intermediate crop species presenting a trait gradient (six replicates per specie for a total of 180 pots). The main leaf traits (P, Mn and Ca concentrations, N/P and SLA) and root traits (i.e. release of organic acids and protons released, phosphatase activity) involved in P acquisition and the changes in soil P pool (soluble P, resin P, Olsen P, microbial P and organic P) were measured. Multivariate analysis of leaf and root functional traits involved in P acquisition and P availability showed an economic spectrum of traits and several global P-acquisition strategies. As covariation between traits and their organisation in different P-acquisition strategies were soil-dependent, designing the functional structure of intermediate crops to maximise ecological complementarities should be performed taking soil type into account.

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Single-cell approach to probing phosphate solubilizing bacteria in by Raman spectroscopy with D2O labelling

Hong-Zhe Li1, Li Cui1, Kai Yang1, Yong-Guan Zhu1 1Key Lab of Urban Environment and Health, Institute of Urban Environment, Chinese Academy

of Sciences, Xiamen 361021, China.

Keywords: Single-cell Raman, PSB, D2O- SIP Phosphorus (P) is an essential nutrient for plant growth, phosphate solubilization bacteria play a key role in soil phosphorus cycling, but remain largely unknown because most of bacteria are uncultured. Hence, it is essential to develop a new method to discern the culture independent phosphate solubilization bacteria at the single-cell level. In this study, we present a culture independent single cell method by combining Raman spectroscopy with D2O-stable isotope probing. The C-D shift is a distinguishable biomarker for active bacteria. By applying this biomarker into the Raman imaging in both artificial media and soil, our results hold promise for Raman based discerning of phosphate solubilization bacteria at single-cell level. This single cell approach will allow us to discern phosphate solubilization bacteria in different habitats and excavate the uncultured microbial resources.

Figure 1: Photomicrograph and Raman images of soil communities incubated in the dissoluble-P free soil for 24h. The yellow regions were identified as bacteria (a), the red regions were identified as PSB (b), the purple circles were identified as PSB (c), and the red circles were identified as non-phosphate releasing bacteria and the green circles were identified as non-living things.

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Effects of element inputs on P-solubilizing bacteria and on phosphatase activity in six grassland soils in South Africa, USA and England

Widdig, M.1; Schleuss, P. M.; Weig, A.; Guhr, A.; Biederman, L.; Borer, E. T.; Crawley, M. J.; Kirkman, K. P.; Seabloom, E. W.; Wragg, P. D.; Spohn, M.

1Department of Soil Ecology, Bayreuth Center of Ecology and Environmental Research (BayCEER), University of Bayreuth, Dr.-Hans-Frisch-Str. 1-3, 95448 Bayreuth, Germany

Keywords: phosphate solubilization, 16S rRNA, phosphatase activity Phosphorus (P) limits plant growth in many soils and its availability is strongly affected by microorganisms that mineralize organic P via extracellular enzymes and solubilize bound inorganic P. We studied how processes of microbial P mobilization and community composition are affected by N and P availability in six grassland soils in South Africa, the USA and England fertilized with nitrogen (N) and P in a full factorial design (Ctrl, +N, +P, +NP). We screened for P-solubilizing bacteria (PSB) based on Pikovskaya medium, determined the relative abundance of PSB (percentage PSB of all colony forming units), and identified PSB based on 16S rRNA. In addition, we analyzed phosphatase activity, microbial biomass carbon, microbial community composition (using ARISA) and soil chemical properties. The proportion of PSB ranged between 0.3 and 56 % of all colony forming units across all soils and treatments. A soil in England had the lowest proportion of PSB with an average of 4.2 % PSB and one of the African sites had the highest proportion with 32.2 % PSB. The proportion of PSB was equal or lower in the second soil depth increment (15 - 30 cm) than in the topsoil (0 - 15 cm), whereas total P, available P and available N were generally higher in the topsoils. The proportion of PSB was across all soils 44 % - 72 % lower in the topsoil and the second soil depth increment, respectively, of N+P fertilized sites compared to non-fertilized sites. The relative change in the proportion of PSB correlated negatively with the relative change in dissolved N in the topsoils. In contrast, phosphatase activity was positively correlated with dissolved N and was significantly higher in the N fertilized treatments than in the P fertilized treatments in the topsoils. Microbial biomass carbon and community composition did not differ significantly between the treatments. However, the composition of the PSB communities was treatment- and site-specific. Most PSB belonged to Pseudomonas sp., Acinetobacter sp., Paraburkholderia sp., Burkholderia sp., and Enterobacterales. PSB with very strong P solubilization capacity mainly belonged to the genus of Acinetobacter. Taken together, this is the first study showing that combined NP fertilization leads to strong decreases in the abundance of PSB in grassland soils on different continents.

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Response of soil phoD and pqqC genes communities to long-term

application of organic-inorganic compound fertilizer with reduced

phosphorus fertilizer

Qing-Fang Bi1,2, Li Cui2, Xian-Yong Lin1, Yong-Guan Zhu2

1 MOE Key Laboratory of Environment Remediation and Ecological Health, College of

Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China

2 Key Lab of Urban Environment and Health, Institute of Urban Environment, Chinese Academy

of Sciences, Xiamen 361021, China

Keywords: phoD gene community, pqqC gene community, reduced phosphorus

fertilization

The bacterial phoD and pqqC genes encode alkaline phosphatase and inorganic

phosphate solublizing bacteria, which are essential to facilitate insoluble phosphorus

(P) mobilization. However, how phoD and pqqC gene communities respond to long-

term fertilization with reduced chemical fertilizer remains largely unknown. Thus, we

conducted a field experiment to investigate the effects of organic-inorganic

compound fertilizer with reduced P fertilizer on the phoD and pqqC gene

communities using high-throughput sequencing in a rice-rice cropping system over

4 years. Results showed that the phoD gene community diversity in the conventional

chemical fertilizer and organic-inorganic compound fertilizer treatments were

significantly increased, but no significant differences in pqqC gene community.

Moreover, the phoD and pqqC gene community compositions were distributed into

three groups in Redundancy analysis (RDA) plot and showed significant correlations

with Hedly-P pools and phosphatase activities. Specifically, striking differences for

enrichment OTUs assemblage of the phoD and pqqC gene communities showed

“organic and chemical fertilizer effect”, and Alphaproteobacteria,

Betaproteobacteria, Deltaproteobacteria, Gammaproteobacteria and Bacilli were

predominant in the enrichment classes. Our results indicate that a similar significant

capacity of phosphate solubilization were found both in the conventional chemical

fertilization and the combinations of organic-inorganic fertilization with reduced P

fertilizer, by reshaping soil phoD- and pqqC-encoded bacterial communities and

altering soil pH and phosphatases activities.

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Mechanisms of plant phosphorus acquisition in intercropping: The role of phosphatase activity and pH in the rhizosphere

Ulrike Schwerdtner1, Marie Spohn1 1Soil Biogeochemistry, Bayreuth Center of Ecology and Environmental Research (BayCEER),

University of Bayreuth, Dr.-Hans-Frisch-Straße 1-3, 95448 Bayreuth, Germany.

Keywords Intercropping, P acquisition, rhizosphere Several studies have shown in the last few years that intercropping can contribute to an increased P uptake of plants resulting in higher yields and improved grain nutritional quality. However, the underlying mechanisms of the increased P acquisition are not yet fully understood. Potential mechanisms leading to increased P acquisition are (i) increased phosphatase activity in the rhizosphere of companion plants that is beneficial for the main culture plant, (ii) high proton and organic acid exudation of the companion plant that mobilize otherwise-unavailable forms of P, (iii) niche complementarity of the roots, and (iv) shifts in the microbial community induced by the companion plant that are beneficial for the main culture. The aim of this study was to test these potential mechanisms of P acquisition of maize in an intercropping experiment. We investigated pH changes, phosphatase activity, root architecture and microbial community composition in the rhizosphere of maize (Zea mays) intercropped with either faba bean (Vicia faba), soybean (Glycine max), blue lupin (Lupinus angustifolius), or white mustard (Sinapis alba), or in monoculture. For this purpose, plants were grown in rhizoboxes with an inner size of 29 x 49 x 3 cm that were inclined by 50° to make the roots grow at the bottom wall of the rhizobox, which could be opened. Phosphatase activities were investigated by soil zymography, pH changes were assessed qualitatively for color changes with bromocresol purple pH-indicator agar, root architecture was determined using a root scanner and microbial community composition was assessed by ARISA. First results suggest that interactions of roots of maize and the companion plant lead to increased P acquisition of maize.

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Identification of Medicago truncatula phosphate transporter 1 (MtPHO1) homologues that are involved in rhizobium symbiosis

Ngoc Nga Nguyen1, Nathan A. Riva1, Damien De Bellis2, Yves Poirier1 1Department of Plant Molecular Biology, Biophore Building, University of Lausanne, 1015

Lausanne, Switzerland. 2 Electron Microscopy Facility, Biophore Building, University of Lausanne, 1015 Lausanne,

Switzerland.

Keywords: PHO1, phosphate transporter, nitrogen fixation Phosphorus is an essential macronutrient element necessary for the symbiotic Rhizobium in nodules and high nitrogen fixation rates. This element is delivered into the bacterial symbiosome by the host plant through unknown phosphate transporters. Members of the phosphate exporter family PHO1 were identified in the model legume Medicago truncatula and their expression patterns in nodules were determined. Among seven members of MtPHO1 family, three genes named MtPHO1.1, MtPHO1.2 and MtPHO1.3 were expressed in the nodules. Furthermore, MtPHO1.1 and MtPHO1.2 were expressed in the whole nodule while MtPHO1.3 was expressed only in the peripheral vasculature of nodules. Transposon insertion mutants in either MtPHO1.1 or MtPHO1.2 did not result in detectable phenotype on nodulation and nitrogen fixation, indicating potential redundancy between these two genes. RNAi constructs targeting simultaneously both MtPHO1.1 and MtPHO1.2 genes were expressed under the control of a nodule-specific promoter (NCR001) in hairy root transformants. Results showed that the morphology of nodules of RNAi plants was modified compared to controls. There were also less bacteroids in the nodules of RNAi plants as compared to WT plants. Further work is aimed at analyzing the repercussion of the down-regulation of MtPHO1.1 and MtPHO1.2 genes on nitrogen fixation and Pi transport in the symbiosomes. References - Hamburger D, Rezzonico E, MacDonald-Comber Petétot J, Somerville C, Poirier Y (2002) Identification and characterization of the Arabidopsis PHO1 gene involved in phosphate loading to the xylem. Plant Cell 14:889-902 - Million Tadege, Jiangqi Wen, Ji He, Haidi Tu, Younsig Kwak, Alexis Eschstruth, Anne Cayrel, Gabi Endre, Patrick X. Zhao, Mireille Chabaud, Pascal Ratet and Kirankumar Mysore (2008) Large scale insertional mutagenis using Tnt1 retrotransposon in the model legume Medicago truncatula. The Plant Journal 54 (2):335-347

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Improving phosphorus efficiency of white clover (Trifolium repens L.) through interspecific hybridisation with wild relatives

Shirley Nichols1, Jim Crush, Rainer Hofmann, Warren Williams 1AgResearch, Ruakura Research Centre, Hamilton, New Zealand

Keywords: White clover, hybridization White clover (Trifolium repens L.) is a major pasture legume in New Zealand, which competes poorly with grasses for soil phosphorus (P). This results in high fertiliser rates, or low clover productivity where this is difficult or expensive. The aim of this work is to improve white clover's adaptation to low soil P by introducing traits through interspecific hybridisation with wild relatives. We focused on hybrids with T. uniflorum, a closely related wild species from the Mediterranean. Potential for low P tolerance was initially observed in sand culture, and subsequent work was done in a silt loam soil to which CaHPO4 was added to produce a range of "on-farm" soil P levels. Shoot dry weight (DW) of T. uniflorum and first generation backcross hybrid families was higher than white clover parental cultivars, and shoot %P levels were below the critical value for white clover. Decreasing nutrient solution concentrations had smaller effects on shoot DW of hybrids than white clover, and the proportion of P in inorganic form was lower in families that were least affected. Differences in root branching and architecture were also observed in hydroponics. In soil, shoot DW was also higher in some hybrids compared with white clover at low soil P levels. These had higher rates of root branching and a root:shoot ratio that was highly responsive to changes in soil P. In other experiments, P was stored below grazing height in T. uniflorum (roots) and some hybrids (stolons) as P supply increased. Higher shoot DW of hybrids, at a %P below the critical level for white clover, indicated tolerance for low soil P, which was confirmed in further experiments. Root branching patterns that may increase P acquisition, less inorganic P sequestered in vacuoles, responsiveness of DW partitioning to P supply, and storage of P below grazing height are possible edaphic adaptations inherited from T. uniflorum. In conclusion, hybridisation with T. uniflorum can improve growth of white clover at low soil P, by introducing new genetic variation. Variation among hybrids provides potential for selection, and ongoing work on genetic tools and phenotyping traits will aid development of improved cultivars.

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Quantitative measurement of phosphatase activity distribution in the rhizosphere – impact of root hairs

Timothy S. George1, Courtney D. Giles1, Gustavo Boitt2, Lionel Dupuy1, Lawrie K. Brown1, Leo Condron2

1The James Hutton Institute, Invergowrie, Dundee, DD2 5DA 2Lincoln University, Bioprotection Research Centre, Lincoln 7647, Christchurch, New Zealand

Keywords: Phosphatase, soil zymography, rhizosphere Organic phosphorus (Po) compounds play key roles in biological and ecosystem function, being critical to cell function, growth and reproduction and understanding the functionality of phosphatase enzymes at the soil root interface is critical to this. Zymographic methods for the 2D distribution of phosphatase activity in soils have markedly advanced our understanding of root-soil-microbiota interactions in recent years.The majority of 4-methylumbelliferylphosphate (4-MUP) based zymography studies are qualitative; however, robust quantitative approaches are needed to advance a mechanistic understanding of enzyme behaviour in soils. In this study, we present an optimised method for phosphatase zymography in rhizobox studies, involving (1) a systematic evaluation of 4-methylumbelliferone (4-MU)-based calibration functions in relation to image exposure time and (2) the development of advanced image analysis tools for lateral and longitudinal distributions of phosphatase along barley roots (Horduem vulgare L., cv Optic). We applied this improved technique to study the distribution of phosphatase activity associated with barley roots with and without root hairs. Exposure time (<1s to 32s) affected the slope and intercept of 4-MU calibration equations by 4.4- and 5.8-fold, respectively, and diminished the linearity of calibration relationships at longer exposures due to photosaturation. An eight second deviation in the calibration exposure time resulted in a 50% error in estimates of phosphatase activity around barley roots. Phosphatase activity measured at set distances from the root tips revealed the relationship between root hair length and maximum phosphatase activity in lateral as well as longitudinal integrated root profiles. Careful consideration of calibration conditions and the adoption of advanced image analysis techniques are therefore recommended to expand the quantitative capacity of fluorescence-based zymography. This technique can now be used to understand interactions at the root soil interface which impact organic P availability.

Figure 1. Effect of root hair length and distance from root tip on acid phosphatase activity near barley roots.

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The effect of phosphate starvation on the early pre-mitotic phase of lateral root development

Hanne Crombez1,2, Hans Motte1,2, Alexa De Knijf1,2, Boris Parizot1,2, Tom Beeckman1,2 1Department of Plant Biotechnology and Bioinformatics, Ghent University, Technologiepark

927, 9052 Ghent, Belgium 2Center for Plant Systems Biology, VIB, Technologiepark 927, 9052 Ghent, Belgium

Keywords: Lateral root, Phosphate starvation Phosphorous is indispensable for plant growth, but is very often unavailable for uptake, either because it is not present in the soil or because it is retained in the soil. To tackle this, plants have developed a range of strategies to obtain phosphate from the environment, such as upregulation of transporters, excretion of acids and acid phosphatases and altering root system architecture. Signaling pathways and uptake mechanisms in response to phosphate deprivation has been extensively studied, but in particular the signaling leading to the phosphate starvation-induced lateral root formation remains unclear. In this study, we aim to identify new molecular players involved in lateral root development upon phosphate starvation. Therefore, using an auxin response Arabidopsis DR5-luciferase line, we first observed that phosphate starvation had an effect on early auxin signaling and the number of pre-branch sites (Figure 1).

Figure 1: DR5 luciferase signal in high (left) and low (right) phosphate conditions. Phosphate deprivation leads to more prebranch sites and a stronger DR5 signal compared to normal phosphate conditions.

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Due to this early effect, we selected early lateral root initiation microarrays and performed a meta-analysis to identify candidates involved in the phosphate starvation-induced lateral formation. More specifically, we looked for genes differentially expressed during lateral root initiation specific in lateral root founder cells (De Smet et al., 2008) or between wild-type Arabidopsis and the lateral rootless solitary root mutant (Vanneste et al., 2005) that are also induced upon phosphate starvation. This led to a number of lateral root-related genes that showed a phosphate starvation response. To evaluate their importance in the phosphate starvation-induced lateral root formation, mutants in the hit genes were tested in different phosphate conditions for their effect on lateral root formation. In addition, reporter lines were generated to evaluate their expression. As such, we identified a number of genes related to phosphate starvation and lateral root formation and verified their importance in the phosphate starvation induced lateral root formation. References - De Smet, I., et al (2008) Receptor-like kinase ACR4 restricts formative cell divisions in the Arabidopsis root. Science 322, 594-597. Vanneste, S., et al (2005) Cell cycle progression in the pericycle is not sufficient for SOLITARY ROOT/IAA14-mediated lateral root initiation in Arabidopsis thaliana. Plant Cell 17, 3035-3050

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Effects of a short-term fertilization on microbial community structure and phosphatase harboring microorganisms in temperate forest soils

Maja Siegenthaler, Emmanuel Frossard, Éva Mészáros Group of Plant Nutrition, Institute of Agricultural Sciences, Department of Environmental

Systems Science, ETH Zurich, Eschikon 33, 8315 Lindau, Switzerland

Keywords: Short-term fertilization trial, forest microbial community, molecular fingerprinting Forest trees, as most plants in terrestrial ecosystems, take up their phosphorus (P) mainly as phosphate from the soil solution. The phosphate in soil solution is then replenished by abiotic and biotic processes. The soil microbial community plays a key-role in replenishing the soil solution by mediating mineralization of organic compounds through enzymatic hydrolysis. Among other enzymes, extracellular phosphatases that convert organic P into phosphate are excreted by microbes. So far, several alkaline (phoA, phoD, phoX) and acid (acpA, appA) phosphatase genes encoding for the corresponding alkaline and acid phosphatase enzymes are known. Our study is part of the German priority program "SPP 1685 - Ecosystem Nutrition". In this framework a two-year long fertilization experiment was set up at two contrasting beech forest field sites in Germany: a site with a soil containing high amount of available P and another with a soil presenting little available P. The overall objective of the program was to investigate the importance of soil organic matter turnover on P cycling under environmental changes induced by fertilization (Figure 1). Part of our study focuses on changes in the microbial community structure. Microbes are the drivers of soil organic matter turnover and are also sensitive to changes of available nutrient concentrations in the environment. A special focus lays on the functional genes directly associated with the production of microbial phosphatases.

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Figure 1: Phosphorus fluxes (continuous lines) and interactions (dotted lines, + for positive and - for negative feedback) in the organic horizon of forest soils studied in the project.

The effects of nitrogen (N) and P inputs, added in water-soluble form alone or combined in a full factorial design, are studied at these two sites. The organic horizon has been sampled at several points in time before and after nutrient inputs. DNA was extracted to explore the changes of bacterial and fungal community, as well as phosphatase gene harboring microorganisms. We expect that fertilization causes changes in the diversity of bacterial and fungal as well as acid and alkaline phosphatase harboring microbial community. In detail, N addition is mainly thought to affect the bacterial and fungal community structure, but not the community composition. On the contrary, P addition is expected to additionally affect the phosphatase harboring microbial community since the need for organic P mineralization might decrease. Changes in the phosphatase harboring microbial community are assumed to be more pronounced in the soil with little available P.

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Plant growth - promoting bacteria as fertility tools for phosphorus deficient and salt

affected soils Tchuisseu Tchakounté Gylaine Vanissa1,4,5 , Beatrice Berger2, Sascha Patz3, Fankem Henri4, Silke

Ruppel1

1Leibniz Institute of Vegetable and Ornamental Crops, Grossbeeren/Erfurt e.V, Theodor-Echtermeyer-Weg 1, 14979 Grossbeeren, Germany

2Institute for National and International Plant Health, Julius Kuehn-Institute-Federal Research Centre for Cultivated Plants, Messeweg 11/12, 38104 Braunschweig, Germany.

3Algorithms in Bioinformatics, Center for Bioinformatics, University of Tuebingen, Sand 14, 72076 Tuebingen, Germany.

4Department of Plant Biology, Faculty of Sciences, University of Douala, P.o.Box:24157 Douala, Cameroon.

5Faculty of Life Sciences, Humboldt-University of Berlin, Invalidenstrasse 42, 10115 Berlin, Germany.

Keywords: Bacteria, phosphorus stress, plant growth Applying bacterial inoculum which increase the availability of nutrients in the soil and augment tolerance to abiotic stresses is an alternative to improve plant growth and crops productivity in an environmental eco-friendly way. It is well known that plant growth-promoting (PGP) bacteria can enhance plant growth either under phosphorus starvation or saline condition. But the bacterial effect on plant under the combination of both stresses is still limited. To address this challenge, bacteria were isolated from acidic and salt affected soil of Cameroon and identified by partial 16S rRNA gene sequencing. The isolates were screened for their phosphate solubilizing ability on agar plates supplied with tricalcium phosphate, hydroxyapatite and rock phosphates (RP) from different origins (Algerian, Cameroonian, Malian, Mexican and Moroccan PR) as well as their potential to tolerate increasing concentrations of salt, to fix nitrogen and to produce siderophores. A total of 143 bacterial isolates were identified and assigned to 20 genera. Based on their in vitro characterization, 50.4% solubilized phosphate regardless the type of phosphate source, 88.1% were salt tolerant at 2% NaCl, but only 16.8% could tolerate 8% NaCl, 10.5% possessed the nifH gene and 19.6% produced siderophores. Among the different inorganic phosphate sources tested, tricalcium phosphate with 46.2% was the phosphate source most easily solubilized whereas Moroccan RP with only 2.8% was the most recalcitrant. Six isolates affiliated to the most abundant genera identified, Bacillus and Arthrobacter, carrying multiple or single tested PGP traits were selected and their effect on growth and phosphorus (P) uptake of tomato plants was investigated in greenhouse under different combinations of P and salt stresses. In general, two bacterial strains composing of all tested PGP traits showed best plant growth-promoting results under all growth conditions. Our results indicate the potential of using native bacterial strains to enhance soil fertility and plant growth under specific stress conditions in Cameroon. Finally, their performance under field conditions should be assessed before being recommended for commercial applications.

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Complexity of Pi uptake regulation in plants Satomi Kanno1, Pascale David1, Hélène Javot1, Thierry Desnos1, Tomoko Nakanishi2, Marie-

Christine Thibaud1, Laurent Nussaume1

1Laboratory of Plant Development Biology- UMR 7265 CEA/CNRS/University of Aix-Marseille- CEN Cadarache 13108 St Paul lez Durance. France

2Laboratory of Radio Plant Physiology,The University of Tokyo. 1-1-1Yayoi, Bunkyoku, Tokyo.

Keywords: High affinity Pi transporters, transcriptional and post-transcriptional regulations, phosphate uptake Phosphate (Pi) is a crucial and often limiting nutrient for plant growth. Its uptake relies on the presence of multiple high affinity transporters (PHT1 family) located in the plasma membranes (Nussaume et al., 2011). Multiple steps of transcriptional and post-transcriptional regulations (phosphorylation, degradation) of these proteins were identified illustrating the capacity for plants to tightly control the level of these transporters into the cells (Misson et al., 2004; Misson et al., 2005; Thibaud et al., 2010; Bayle et al., 2011; Chen et al., 2015). Combining several genetic approaches we have investigated the physiological role of these proteins (Ayadi et

al., 2015), and try to unravel the contribution of specific layers to Pi uptake (Kanno et al., 2016). Figure 1: Use of Radio imaging combined with genetic tools to demonstrate the role of the root cap in pi uptake (Kanno et al., 2016).

References - Ayadi, A., David, P., Arrighi, J.F., Chiarenza, S., Thibaud, M.C., Nussaume, L., and Marin, E.

(2015). Reducing the Genetic Redundancy of Arabidopsis PHOSPHATE TRANSPORTER1 Transporters to Study Phosphate Uptake and Signaling. Plant Physiol 167; 1511-1526.

- Bayle, V., Arrighi, J.F., Creff, A., Nespoulous, C., Vialaret, J., Rossignol, M., Gonzalez, E., Paz-Ares, J., and Nussaume, L. (2011). Arabidopsis thaliana High-Affinity Phosphate Transporters Exhibit Multiple Levels of Posttranslational Regulation. Plant Cell 23; 1523-1535.

- Chen, J., Wang, Y., Wang, F., Yang, J., Gao, M., Li, C., Liu, Y., Liu, Y., Yamaji, N., Ma, J.F., Paz-Ares, J., Nussaume, L., Zhang, S., Yi, K., Wu, Z., and Wu, P. (2015). The rice CK2 kinase regulates trafficking of phosphate transporters in response to phosphate levels. Plant Cell 27; 711-723.

- Kanno, S., Arrighi, J.F., Chiarenza, S., Bayle, V., Berthome, R., Peret, B., Javot, H., Delannoy, E., Marin, E., Nakanishi, T.M., Thibaud, M.C., and Nussaume, L. (2016). A novel role for the root cap in phosphate uptake and homeostasis. eLife 5.science 2; 83.

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Molecular mechanisms of phosphate delivery via the mycorrhizal pathway Satoshi Asaeda1 Hayato Maruyama1 Tatsuhiro Ezawa1

1Hokkaido University, Sapporo, Japan

Keywords: Arbuscular mycorrhizas, phosphate delivery Arbuscular mycorrhizal (AM) fungi associate with 80% of land plants, promote growth of the host plants through enhanced uptake of phosphate (Pi), and thus play an important role in phosphorus cycling in terrestrial ecosystems. AM fungi colonize the roots and form arbuscules where Pi and carbon source are exchanged. At the same time, the fungi construct hyphal networks in the soil, through which Pi is taken up, accumulated as polyphosphate (polyP) in the vacuoles, and translocated to arbuscules. However, the molecular mechanism underlying Pi delivery and export has not been well understood. Here, we employed comparative transcriptome analysis toward a comprehensive understanding of the mutualism of the association at the molecular level. Rhizophagus clarus HR1 was grown in association with Nicotiana benthamiana under Pi-deficient conditions for 9 weeks in the mesh-bag separated two-compartment culture system in which mycorrhizal and hyphal compartments (MC and HC, respectively) were separated. After applying 1mM Pi to the HC, extraradical mycelia in the HC and mycorrhizal roots in the MC were collected 0, 12, 18, 24, and 36 h after Pi application. PolyP contents were measured, and mRNA was purified for 75 bp single-end sequencing on the illumina NextSeq platform. The sequence reads were mapped on the reference sequences of N. benthamiana and R. clarus, and differentially expressed genes were defined with a false discovery rate threshold of 0.05. PolyP accumulation in extraradical mycelia occurred immediately after Pi application, during which not only the genes involved in Pi uptake and polyP synthesis but also those involved in cation uptake were upregulated, responsible for maintaining cellular charge neutrality. PolyP levels in extraradical mycelia were gradually decreased upon translocation to intraradical mycelia in which increases in polyP level were observed 12 h after Pi application. Dissection of the molecular processes for Pi export to the host are currently undertaken with respect to transcriptome responses to polyP translocation in intraradical hyphae.

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Phosphorus immobilization strategies by microorganisms d epending on their activation

Nataliya Bilyera 1, 2, Evgenia Blagodatskaya 2, Deejay Maranguit 3 , Yakov Kuzyakov 4 1 Dept. of Radiobiology and Radioecology, NULES of Ukraine, 03041, Kyiv, Ukraine, 2 Dept. of Agricultural Soil Science, University of Göttingen, 37077, Göttingen, Germany, 3 Dept. of Soil

Science, Visayas State University, Baybay, 6521-A Leyte, Philippines, 4 Agro-Technological Institute, RUDN University, 117198 Moscow, Russia

Keywords: Microbial P, soil ATP, phosphatase

Facilitating phosphorus (P) immobilization by microorganisms may improve

fertilizers efficiency and prevent P losses from agricultural fields to adjacent

ecosystems and to the hydrosphere. However, the underlying processes and

mechanisms of microbial P immobilization are still poorly understood. We aimed to

define the drivers of P immobilization by supplying contrasting P amounts into low P

Cambisoil during the 120 hours incubation experiment at three carbon addition

levels.

The treatments were i) no C (С0), ii) multiple C addition (10 µg C g-1 soil à day-1) –

C10x5, and iii) single C addition (50 µg C g-1 soil) – C50. Three P rates were applied at

each soil: i) no P (P0); ii) 10% P from initial soil P (P10); and iii) 50% P from initial soil

P (P50).

The peak values of the molar C:P ratio in microbial biomass (366-1042 vs. 66-310)

were detected at P0 in all C treatments. Phosphatase production strongly increased

(R2=0.79) with C:P ratio during the first 24 h, but this relationship became weaker

(R2=0.49) until 120 h. Phosphatase activity decreased linearly (R2=0.84-0.89) with

higher P immobilization rates for C50 and C10x5, but remained almost constant

without glucose addition.

Microbial P (Pmic) increased linearly with P input during 120 h at all C levels (R2=0.68-

0.95). However, P application had more pronounced effect at C50 and C10x5

treatments, because C input limits the size of microbial biomass pool which

immobilizes P. Soil adenosine triphosphate (ATP) increased with P levels in all C

treatments, but the ATP content remained similar in activated and non-activated

microorganisms.

Microbial P immobilization strategies were dependent on the activation by glucose.

Non-activated microorganisms allocated P mainly in ATP, while activated ones

tended to increase the Pmic by maintaining the same ATP level. Additionally, non-

activated microorganisms immobilized P directly from the added source, when the

activated ones accelerated phosphatase activity due to changed C:P stoichiometry,

and then they immobilized P.

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Effects of P-efficient legumes on fractionated rhizosphere P of various P-limited soil types in Japan

Soh Sugihara1, Kaoru Imai1, Jun Wasaki2, Haruo Tanaka1 1Graduate School of Agriculture, Tokyo University of Agriculture and Technology, Fuchu, Tokyo

183-8509, Japan 2Graduate School of Biosphere Science, Hiroshima University, Japan

Keywords: P-efficient legume, Rhizosphere, less labile P Context; Phosphorus (P) is an essential nutrient for crop production, though the P resource is limited and may be exhausted worldwide in the near future. Most soil P is associated with Al and Fe in the form of less labile P in acidic soils of Japan, and it is necessary to utilize the less labile P in crop production and improve the P use efficiency, by using P-efficient plants as green manure or intercropping. Objective; To evaluate the effects of two contrasting P-efficient legumes (white lupin, WL (Lupinus albus L.); and groundnut, GN (Arachis hypogaea L.)) on rhizosphere soil P dynamics of different P-limited soil types in Japan as explained below. Methods; We conducted a 56-day pot experiment in the phytotron, and measured the plant P uptake and fractionated P of rhizosphere and bulk soils, based on the Hedley-fractionation method. We collected and used the volcanic soil (Andisols), sandy soil (Entisols), and strongly weathered Red-yellow soil (Inceptisols), with or without fertilization management soils (totally 3 soil types * 2 different management = 6 soils). Results and Discussion; Plant P uptake was generally larger in GN than WL in each soil type and P treatment, except for P-fertilized Red-yellow soil. In Andisols, which has much non-crystalline Al and mineral associated organic matter, both WL and GN cannot solubilize the less labile (NaOH extractable) inorganic P (Pi) and organic P (Po) in non-P fertilized acidic plot (soil pH=5.3), though both WL and GN can solubilize the less labile Pi (but not less labile Po) in P-fertilized plot (soil pH=6.7). In Sandy soil, which has small total P and available P, both WL and GN did not decrease the less labile P in P fertilized plot (soil pH=4.4), while WL did decreased the less labile Pi a little in non-P fertilized plot (soil pH=5.5). In Red-yellow soil, which has much crystalline Fe of soil, WL clearly decreased the less labile Pi and Po substantially in P-fertilized plot (pH=5.1), though GN did not. It suggests that WL effectively solubilize and/or mineralize the less labile Pi and Po (possibly associated with crystalline Fe) under the P-fertilized Red-yellow soils, while GN cannot. Conclusion; To utilize the less labile P of soils by P-efficient legume, it is necessary to consider the soil conditions, such as soil pH, the amount of Al/Fe oxide, and history of P fertilization. Our results suggests that WL is suitable to utilize the less labile Pi and Po of crystalline Fe soils, compared with GN.

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Improving phosphate-use efficiency in grass-clover pastures Rebecca Yeates1,2, Jim Crush1, Shirley Nichols1, Mike Clearwater2

1AgResearch, Ruakura Research Centre, Private Bag 3123, Hamilton 3216, New Zealand. 2University of Waikato, Private Bag 3105, Hamilton 3240, New Zealand

Keywords: Root hairs, PO4 uptake, competition Context: Perennial ryegrass (Lolium perenne L.) out-competes white clover (Trifolium repens L.) for soil phosphorus [P], resulting in a requirement for P fertiliser rates on mixed swards to be three times higher than when the species are grown separately. The elevated P fertiliser rates result in additional economic costs to farmers, and higher environmental costs associated with P losses to waterways. Perennial ryegrass is highly adapted for P acquisition, probably reflecting it evolution on old forest margin soils low in available P. It has long, dense root hairs compared to white clover, which increases the root absorptive surface area for P uptake. Methods and Results: Ryegrass populations with contrasting root hair length and density were selected using the Rhizosheath Selection Tool (RST) – a method for rapid screening of young seedlings for these traits. The low rhizosheath ryegrass population had shorter, sparser root hairs on seminal roots, and sparser root hairs on adventitious (adult) roots than the high rhizosheath population. Plants derived from tiller cuttings from selected genotypes of the two populations were grown at five soil P levels in a glasshouse experiment. Selection for contrasting rhizosheath size had no effect on P acquisition or growth of the ryegrasses. The two ryegrass populations were then grown with companion white clover in soil with Olsen P levels of 12 and 19 mg L-1. Clear perspex partitions were used to separate the shoot systems and avoid shoot competition for light. The low rhizosheath ryegrass was less competitive for P against the companion white clover in the Olsen P 12 mg L-1 soil, resulting in a 30% increase in clover shoot dry weight (DW), with no difference in ryegrass shoot DW. In the Olsen P 19 mg L-1 soil there was no rhizosheath selection effect on white clover or ryegrass growth. Conclusion: This research highlights the importance of root traits in forage plant breeding, and the potential environmental and economic benefits a low rhizosheath perennial ryegrass could have in New Zealand’s pastoral farming systems.

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The role of root morphology and AM colonization on copper and iron uptake, accumulation as affected by phosphorus application in maize

Wei Zhang, Xinping Chen, Chunqin Zou College of Resources and Environment, China Agricultural University, Yuanmingyuan West Road

2, 100193 Beijing, China

Keywords: Phosphorus, Copper and iron, Uptake Although excessive phosphorus (P) fertilizer is applied into farmland to obtain enough grain yield, less information is gotten about the effect of large P application on copper (Cu) and iron (Fe) concentrations, especially the mechanism based on the root morphology and arbuscular mycorrhizal (AM) colonization in maize. A field experiment with six P levels and a pot experiment was conducted to confirm the effect of P application on root and shoot Cu and Fe uptake. P application increased root dry weight to 12.5 kg ha-1 then plateaued at a higher P input, while the critical P rates for root length density and root surface area was 25 kg ha-1. P application significantly decreased Cu concentration in root (Figure 1a), straw, and grain but had no effect on root Fe concentration (Figure 1b). Root AM colonization decreased with increasing P application. The decrease of root AM colonization as affected by P application resulted in the reduction of Cu concentration in root and shoot. The pot experiment further showed benomyl application reduced 27.5% of root Cu concentration and 12.5% of shoot Cu concentration. While, root morphology as affected by P application had no effect on Cu and Fe concentration in this condition.

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Figure 1: Effect of P application on root Cu (a) and Fe (b) concentration of maize

In conclusion, the reduction of Cu concentrations as affected by P application could be partly explained by decrease of AM colonization, while was not related to changes of root morphology. Root Fe concentration was not limited by P application. References

- Liu A, Hamel C, Hamilton R I, Ma B L and Smith D L (2000) Acquisition of Cu, Zn, Mn and Fe by mycorrhizal maize (Zea mays L.) grown in soil at different P and micronutrient levels. Mycorrhiza 9, 331-336.

- Baldi E, Miotto A, Ceretta C A, Quartieri M, Sorrenti G, Brunetto G and Toselli M (2018) Soil-applied phosphorous is an effective tool to mitigate the toxicity of copper excess on grapevine grown in rhizobox. Scientia Horticulturae 227, 102-111.

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Phosphorus mobilization processes from death microbial biomass by beech (fagus sylvatica), determined by isotopic tracing.

Marius Schmitt1, Sebastian Loeppmann1, Klaus A. Jarosch2, Sandra Spielvogel3, Michaela Dippold1

1Biogeochemistry of Agroecosystems, Georg-August-University Göttingen, Germany 2Institute of Geography, University of Bern, Hallerstrasse 12, 3012 Bern, Switzerland

3Institute of Soil Science, University of Kiel, Germany

Keywords: Microbial necromass, P-mobilization Soil microorganisms can influence the quantity of plant available phosphorus (P) both actively and passively. Active mechanisms are biogeochemical transformation- and mobilization processes (mineralization, immobilization), while passive mechanisms are the provision of a stock of P in form of death microbial biomass, i.e. microbial necromass. This microbial necromass can potentially be accessed by other biota to satisfy their demand for P. In a pot experiment we aim to determine which role microbial necromass is playing when it comes to providing P for plant nutrition, depending on the soil P status. We also want to determine which processes are involved in the mobilization of P from microbial necromass (direct root uptake vs. uptake mediated by mycorrhizal fungi). For that, beech (fagus sylvatica) seedlings were planted in T-shaped pots, i.e. pots with two open horizontal compartments on opposite sides. One compartment was left open (compartment “rhizosphere”: roots + fungal hyphae) while the other compartment was covered with a gauze (20 µm mesh) to prevent root ingrowth (compartment “hyphosphere”: fungal hyphae only). Microbial necromass labelled with 33P will be applied on either end of the compartments, followed by a 13carbon-CO2 pulse labelling of the beech. Each pot compartment and beeches will then be destructively sampled to quantify plant uptake of 33P labelled necromass in different plant parts (aboveground, belowground). Additionally, the plant C-investment and the effect on the soil microbial community structure and ectomycorrhizal fungi will be assessed by soil 13C-PLFA analysis. Thereby, we aim to quantify which pathway (rhizosphere vs. hyphosphere) is most relevant for plant uptake of P from microbial necromass. Additionally, plant’s investment into the P mobilization can be determined by 13C tracing in the soil. Lastly, the microbial communities most involved in this process can be determined by microbial community analysis using 13C-PLFAs. By using four different soils with increasing soil P availability we aim to quantify differences in soil P mobilization in dependence of soil P status.

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P acquisition and use efficiency of two Japonica rice cultivars with contrasting tolerance to P deficiency

DMSB Dissanayaka1,2, M. Sueyoshi3, Y. Tateishi1, S. Nishida1, H. Maruyama4, Keitaro Tawaraya5, Jun Wasaki1,3

1Graduate School of Biosphere Science, Hiroshima Univ., Kagamiyama 1-7-1, Higashi-Hiroshima 739-8521, Japan, 2Faculty of Agriculture, Univ. of Peradeniya, Peradeniya, Sri Lanka, 3School of Integrated Arts and Sciences, Hiroshima Univ., Higashi-Hiroshima, Japan, 4Research Faculty of

Agriculture, Hokkaido Univ., Japan, 5Faculty of Agriculture, Yamagata Univ., Japan. Keywords: Rice, P acquisition, P use efficiency

We have demonstrated that a landrace of Japonica rice, Akamai (Yamagata) exhibits low-P tolerance compared to a conventional cultivar, Koshihikari (Dissanayaka et al. 2017). The low-P tolerant traits of Akamai could be useful to breed rice cultivars less dependent on P fertilizer. This study aimed to understand the P-deficiency tolerance of Akamai through exploring both P acquisition and recycling under low-P conditions. Akamai and Koshihikari were cultivated until maturity in pots containing low-P soil (Olsen P: 10 mg kg-1) applied 0 (0P) or 100 mg-P kg−1 soil (100P) as Ca(H2PO4)2•2H2O. Seedlings of each cultivar were also hydroponically cultivated for 27 days in nutrient solutions of 0 or 64 µM phosphate (-P or +P treatments, respectively). P replenishment (PR) treatment was conducted by application of 64 µM phosphate to -P plants for 5 days at the end of cultivation. Leaves were separated to two or three parts by their developmental stages at harvest. Biomass, P concentration, polar lipid composition, and mRNA accumulation for several genes involved in P responses were measured. Root growth of Akamai was higher than Koshihikari under P deficient conditions in both soil and hydroponics. In PR treatment, the amount of total P in Akamai was higher than that in Koshihikari. These facts suggest that the higher P accumulation in Akamai under low-P condition is supported by higher root growth. Akamai grown in 0P soil had remarkably lower P concentrations in less active vegetative organs (partly and fully senesced leaves) than those of Koshihikari, whereas more active organs (green leaves and panicles) contained a greater amount of P. Predominant P allocation to younger parts in Akamai was found during whole cultivation periods in soil culture. Short term P supply after P deficiency also caused higher P accumulation to developing organs of Akamai. Replacement of phospholipids with glycolipids was observed in older leaves of P-deficient rice, especially in Akamai. Increasing rate of mRNA for genes involved in lipid remodeling was greater in Akamai. These results demonstrate the efficient P utilization by Akamai under P deficient conditions. Our findings suggest that both enhanced P acquisition and efficient use of acquired P contribute to the low-P tolerance of Akamai. We have recently isolated a QTL for low-P tolerant of Akamai, qLPT1 (Nishida et al. in press). It is promising for breeding P efficient rice cultivars in future. References - Dissanayaka DMSB, Maruyama H, Nishida S, Tawaraya K, Wasaki J (2017) Landrace of Japonica rice, Akamai

exhibits enhanced root growth and efficient leaf phosphorus remobilization in response to limited phosphorus availability. Plant and Soil 414: 327-338.

- Nishida S, Dissanayaka DMSB, Honda S, Tateishi Y, Chuba M, Maruyama H, Tawaraya K, Wasaki J Identification of genomic regions associated with low phosphorus tolerance in japonica rice (Oryza sativa L.) by QTL-Seq. Soil Science and Plant Nutrition (in press).

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Mobilization of unavailable phosphate in the rhizosphere soil by cluster roots of Helicia cochinchinensis

Tadashi Okamura1, Toshihiro Watanabe2, Hiromi Tsubota3, Jun Wasaki1

1Graduate School of Biosphere Science, Hiroshima Univ., Kagamiyama 1-7-1, Higashi-Hiroshima 739-8521, Japan, 2Research Faculty of Agriculture, Hokkaido Univ., Sapporo, Japan, 5 Graduate

School of Science, Hiroshima Univ., Higashi-Hiroshima, Japan.

Keywords: Helicia cochinchinensis, cluster roots, P solubilization

Under phosphorus (P) deficiency, some plant species of the Proteaceae and legume form unique root architecture like a bottle-brush, so-called cluster root, and secrete a large amount of organic acids and acid phosphatase (APase) from roots to mobilize unavailable P in soils (Shane and Lambers 2005). We have found that Helicia cochinchinensis, which is the only one Japanese species of Proteaceae, formed cluster roots like other Proteaceae (Yamauchi et al. 2015). This study aimed to characterize the ability to mobilize unavailable P in the rhizosphere of H. cochinchinensis grown under low P conditions. Seeds and seedlings of H. cochinchinensis was collected in Miyajima Island, SW Japan and used for sand culture. After 6 months cultivation supplying nutrient solution without P, root exudates were collected for 3h in distilled water as -P treatment. These plants were transplanted into nutrient solution containing 64 µM P, and cultivated for 1 week to collect root exudates as +P treatment. Concentration of citrate and malate in root exudates were analyzed by enzymatic methods. APase activities were also measured using p-nitrophenylphosphate as a substrate. H. cochinchinensis roots were used for activity staining of APase with 5-Bromo-4-chloro-3-indolyl-phosphate. Soil P fractionation was conducted by a sequential fractionation method (Hedley and Stewart 1982).

Fig.1 Correlation between number of cluster roots and exudation citrate under -P

condition. * P<0.01, (Dunnett’s test）

R² = 0,8956

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It was shown that H. cochinchinensis under -P condition secreted much amount of citrate and malate than +P roots. Citrate exudation was positively correlated with the number of cluster roots (Fig.1). APase activity in root exudates was induced by P-deficiency. Histochemical activity staining for APase revealed a strong activity at cluster roots, especially around root surfaces. Soil P fractionation showed that cluster roots of H. cochinchinensis mobilized unavailable P, especially insoluble organic P. We concluded that the strong ability to secrete organic acids and APase in the rhizosphere of cluster roots highly contributed to mobilize unavailable P and uptake P by H. cochinchinensis. References - Hedley M, Stewart J (1982) Method to measure microbial phosphate in soils. Soil Biology and Biochemistry 14: 377-385 - Shane MW, Lambers H (2005) Cluster roots: A curiosity in context. Plant and Soil 274: 101-125 - Yamauchi T, Maruyama H, Uchida S, Mukai S, Tsubota H, Wasaki J (2015) A new finding of cluster roots formed by Helicia cochinchinensis Lour. (Proteaceae). The Journal of Japanese Botany 90: 103-108

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Evaluation of Phosphate solubilizing Pseudomonas isolated from organic tomato crop: biofertilizers

Qessaoui Redouan1,2, Bouharroud Rachid1, Amarraque Abderahim1, Lahmyed Hind1,2, Ajerrar Abdelhadi1,2, Mayad El hassan3, Chebli Bouchra2

1 Research Unit of Integrated Crop Production, Centre Régional de la Recherche Agronomique d’Agadir (INRA), Morocco

2 Biotechnology and Environmental Engineering Team, Laboratory for Process Environmental and Energy Engineering, National School of Applied Sciences, Ibn Zohr University, Agadir,

Morocco. 3 Laboratory of Biotechnologies and Valorization of Natural Resources Faculty of Sciences -

Agadir, Ibn Zohr University, Agadir, Morocco

Keywords: Phosphate solubilization, Pseudomonas The availability of soil Phosphate is largely controlled by biologically mediated processes such as gross mineralization and immobilization rates. The Pseudomonas by their several mechanisms are the most successful bacterial communities able to solubilize phosphates. Five Pseudomonas isolates were isolated from the rhizosphere of organic tomato plants in Agadir region of Morocco. These strains were identified as species of Pseudomonas genus, they were tested for their ability to solubilize phosphate in both solid and liquid media and their effect on tomato plant growth in greenhouse was evaluated. As results, these strains were solubilizing phosphate in both media, and the highest levels of soluble phosphates were obtained by Q122B strain with 11.45 mm of diameter of clear halo around colony in solid medium. In liquid medium the highest levels was obtained by Q111B strain with production of 3.80 mg/ml of P2O5.This Phosphates solubilization is associated with a decrease in the pH of the medium to PH 2.37 compared to the control (PH 7.5). Among these strains, Q111B increase seeds germination by 96% compared to control. Plant growth parameters (shoot length and collar diameter) showed significant increase in response to bacterial inoculation, with an increase in shoot length (45%) and in collar diameter (42%) compared to the control by Q032B and Q146B, respectively. This study shows that the Phosphate solubilizing Pseudomonas will be the potential biofertilizers. The genomic studies were currently in an ongoing way to sequence these strains.

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Root phosphomonoesterase activity as dependent on soil phosphorus availability of common herbaceous plant species of Río de la Plata

grasslands

Diego Michelini1, Andrea Rodriguez, Amabelia del Pino, Hans Lambers, François Teste

1Faculty of Agronomy, Universidad de la República. 780 Garzón Av., Montevideo, Uruguay.

Keywords: phosphomonoesterase, Uruguay, grasslands Río de la Plata natural grasslands harbor a high diversity of plant species on soils spanning a wide gradient of phosphorus (P) concentration. Half of the total soil P concentration is organic P (Hernandez et al., 1995). Although plant diversity is high, most of the herbaceous communities share the same matrix of species, leading to the question: do common species increase their root phosphomonoesterase activity as the resin P concentration of the soils decreases? Objective: Quantify root phosphomonoesterase activity plant species of Río de la Plata grasslands (110 plant species from 21 families), growing in soils spanning a wide range of soil resin P concentrations. Methods: Phosphomonoesterase activity was quantified in roots of common herbaceous species sampled in four plots of six natural grasslands, in Uruguay and South Brazil, following the protocol from Güsewell (2017). Resin P concentration was quantified for the same plots. Linear models were fitted, and ANOVA was performed using R. Results, discussion and conclusions: The resin P concentration of six soils ranged from <1 to 12.5 ng P g-1 soil (p<0.05). From the 16 most common plant species, the correlation of enzyme activity with resin P concentration was negative or there was no trend, but for two species there was a significantly positive correlation (Fig. 1). Carex phalaroides, a sedge, was the only species with a significant negative correlation. The lack of a significant trend among 13 species may be due to the fact that when organic P concentration decreases plants rely on alternative P sources. The diversity of relationships between root enzymatic activity and soil resin P variations may play a role in the maintenance of plant diversity in the most P-depleted soil in natural grasslands of Rio de la Plata. References - Hernández, J., Otegui, O., & Zamalvide, J. P. (1995). Formas y contenidos de fósforo en algunos suelos del Uruguay (No. 43). Universidad de la República, Facultad de Agronomía. - Güsewell, S. (2017). Regulation of dauciform root formation and root phosphatase activities of sedges (Carex) by nitrogen and phosphorus. Plant and Soil, 415, 57-72.

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Facilitated phosphorus acquisition of maize is dependent on the root traits of associated faba bean in intercropping systems

Meijie Qiu1 and Long Li1 1Key Beijing Laboratory of Biodiversity and Organic Farming, College of Resources and

Environmental Sciences, China Agricultural University, Beijing 100193, China.

Keywords: Intercrop, rhizosphere, root morphology Plants deal with phosphorus deficiency by changing the root morphology or strengthening the rhizosphere processes. How does these strategies affect adjacent plants in intercropping? Previous studies have proved that faba bean roots can release proton, acid phosphatase and organic acid to mobilize insoluble phosphorus in soils (Li et al., 2003; 2004; 2007). To our knowledge, however, there is still lack of study on how morphological parameters of faba bean roots affect the phosphorus acquisition of maize. The objectives of the present study is to investigate the root morphological and rhizosphere differences among faba bean varieties and their effects on the growth and phosphorus uptake of associated maize, and to identify the mechanisms of efficient phosphorus acquisition in faba bean/maize intercropping. We designed a greenhouse experiment with two factors, where the first factor is faba bean cultivars (Lincan, Kangleniutabian, Zhangye and Mingqin) with large variation to mobilize sparingly soluble P in soils, and the second factor is root barriers (solid barrier, nylon mesh barrier and no barrier) with 5 replications for each treatment. Results showed that acid phosphatase in rhizosphere soil of cultivar Lincan was 18.4% and 18.7% higher than that of cultivars Minqing and Zhangye. The citrate concentration in rhizosphere soil for cultivar Kangleniutabian was 2.1 times and 2.3 times as much as that of Minqin and Zhangye, and the malic acid concentration was 2.32 times and 2.31 times as much as those of Mingqin and Zhangye. The root length, root surface area and root volume of Lincan are all significantly higher than other cultivars. The rhizosphere processes of faba bean was positively correlated with not only P acquisition of faba bean itself, but also P acquisition of associated maize. The morphological parameters of faba bean roots was negatively correlated with P acquisition of associated maize. In conclusion, the finding has shed a light on understanding the mechanism behind interspecific facilitation on P acquisition, but also have an importance in selecting a reasonable cultivar in intercropping. References - Li L, Li SM, Sun JH, Zhou LL, Bao XG, Zhang HG, Zhang FS (2007) Diversity enhances agricultural productivity via rhizospher phosphorus facilitation on phosphorus-deficient soils. Proceedings of the National Academy of Sciences USA (PNAS) 104: 11192-11196. - Li SM, Li L, Zhang FS and Tang CX (2004) Acid phosphatase role in chickpea/maize intercropping. Annals of Botany 94: 297-303.

- Li L, Tang C, Rengel Z. and Zhang FS (2003) Chickpea facilitates phosphorus uptake by intercropped wheat from an organic phosphorus source. Plant and Soil 248:297-303.

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Identification of phosphorus fractions accessible for arbuscular mycorrhizal fungi: sequential fractionation of hyphosphere soil

Nanako Miyajima1, Soh Sugihara1, Chihiro Okada2 Tatsuhiro Ezawa2, Haruo Tanaka1 1Graduate School of Agriculture, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-

cho, Fuchu-shi, Tokyo 183-8509, Japan 2Graduate School of Agriculture, Hokkaido University, Sapporo, 060-8589, Japan

Keywords: Mycorrhizal fungi, hyphosphere soil, Lotus japonicus L. Phosphorus (P) is an essential nutrient for plants, though most P in the soil is less labile forms such as Al/Fe/Ca-associated inorganic P or organic P. Particularly, plant available P is generally low in acidic soil due to increased solubility of Al/Fe. It is well known that association with arbuscular mycorrhizal (AM) fungi enhances plant P uptake and growth in acidic soil, though it is still unclear that which forms of P are taken up by AM fungi. In the current study, to identify the forms of P taken up by AM fungi, we conducted sequential fractionation of hyphosphere soil and analyzed inorganic P (Pi) and organic P (Po) using three different acidic soils. Lotus japonicus L. was grown in the mesh bag culture system in which hyphal compartments (HC) were separated by 37-µm nylon mesh. In experiment (1) the plants were inoculated with Rhizophagus irregulris R-10, and either Andisols in which non-crystalline Al dominates (pH5.4) or Red-yellow soil that has much crystalline Fe (pH4.6) with or without 100 mg P kg⁻¹ soil was filled in the HC. In experiment (2) the plants were inoculated with R. clarus RF1, and a mixture of acid sulfate soil and river sand (1:4, v/v) with pH3.8, 4.2, and 4.9 to which 100 mg P kg⁻¹ was applied was filled in the HC. After 6-9 weeks, hyphosphere soils were collected from the HC and measured Pi and Po contents after sequential fractionation according to Hedley method. AM fungal inoculation increased plant P uptake in all soils and decreased the labile P fractions, resin-P and NaHCO₃-Pi. It indicates that AM fungi generally absorb the labile Pi. What is more, we also observed the decrease of Po in the NaOH fraction that is less labile, except in the Red-yellow soil. This observation suggests that AM fungal hyphae are capable of taking up the less labile Po, probably through mineralization by their phosphatases.

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Growth and molecular responses of Lolium perenne grown in two Andisols to the inoculation with phosphobacteria along with phosphate fertilization

Patricio Javier Barra1, Sofía Pontigo1, Leyla Parra1, Mabel Fabiola Delgado1, Milko Alberto Jorquera1, Paola Andrea Duran María de la Luz Mora1

1Center of Plant, Soil Interaction and Natural Resources Biotechnology; Scientific and Technological Bioresource Nucleus, Universidad de La Frontera, Temuco, Chile

Keywords: Phosphobacteria, P-transporters, Andisol

Phosphobacteria, secreting organic acids and phosphatases, usually favour plant performance in acidic soils, such as Chilean Andisols, by increasing phosphorus (P) availability. However, it is not well known how phosphobacteria can affect the expression of plant genes that code for P-transporters. Therefore, the aim of this study was to evaluate the single and combined effects of the P fertilization and phosphobacteria inoculation on biomass, P accumulation and P-transporters gene expression of ryegrass For this, a greenhouse assay was performed in two Andisols, Barros Arana (38°58' S 72°53' W) and Gorbea (39°04'S 72°42'W) from Southern Chile, selected based in their contrasting P concentration, 6.0 and 18.0 mg kg-1, respectively. Ryegrass seeds were sown in each soil amended with superphosphate at rates of 0 (control) or 200 mg P kg−1 soil. After germination, seedlings were inoculated twice a week with a bacterial consortium formulated with five phosphobacteria identified as Klebsiella sp.RC3, Stenotrophomonas sp.RC5, Klebsiella sp. RCJ4, Serratia sp. RCJ6 and Enterobacter sp.RJAL6 as described by Mora et al., (2017). Thus, four treatments with three replicates each were established for each soil: (i) Plants without P fertilization and bacterial inoculation (P- B-; control); (ii) Plants without P fertilization and inoculated (P- B+); (iii) Plants with P fertilization and uninoculated (P+ B-) and (iv) Plants with P fertilization and inoculated (P+ B+). After six weeks, dry weight and total P was determined. Whereas, real-time quantitative reverse transcription PCR (qRT-PCR) was performed to evaluate relative expression of P-transporters genes LpPHT1;1 and LpPHT1;4.Our results revealed that biomass and P accumulation in ryegrass were significantly (P ≤ 0.05) increased in presence of P fertilization in both soils. Meanwhile, phosphobacteria inoculation significantly increased the biomass and P-accumulation in shoot of plants grown in both soils, but this effects was observed only when P fertilization was added to the soils. Meanwhile, relative expression of both P-transporters genes was significantly decreased in both soils under P-fertilization. The effect of bacterial inoculation on P-transporter gene expression was less evident. In conclusion, the effect of P fertilization is potentiated for the phosphobacteria inoculation References - Mora, ML, Demanet, R, Acuña, JJ, Viscardi, S, Jorquera, M, et al. (2017). Aluminum-tolerant bacteria improve the plant growth and phosphorus content in ryegrass grown in a volcanic soil amended with cattle dung manure. Appl. Soil Ecol. 115:19–26.

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Impact of P application and cover crop on arbuscular mycorrhizal communities and soybean performance after a 5-year P-unfertilized crop rotation Masao Higo1, Yuya Tatewaki2, Kento Gunji2, Yoshihiro Kawamura2, Isobe Katsunori1

1College of Bioresource Sciences, Nihon University, Kameino 1866, Kanagawa 252-0880, Japan.

2Graduate School of Bioresource Sciences, Nihon University, Kameino 1866, Kanagawa 252-0880, Japan.

Keywords: arbuscular mycorrhizal fungi, phosphorus, soybean The aim of this work is to understand the diversity of arbuscular mycorrhizal fungi (AMF) is important for optimizing their role for phosphorus (P) nutrition of soybeans in P-limited soils. However, it is not clear how soybean growth and P nutrition is related to AMF colonization and diversity of AMF communities in a continuous P-unfertilized cover cropping system (Higo et al., 2014, 2015). Thus, we investigated the impact of P-application and cover cropping on the interaction among AMF colonization, AMF diversity in soybean roots, soybean growth and P nutrition under a 5-year P-unfertilized crop rotation. In this study, we established three cover crop systems (wheat, red clover, and oilseed rape) or bare fallow in rotation with soybean. The P-application rates before the seeding of soybeans were 52.5 and 157.5 kg ha−1 in 2014 and 2015, respectively. We measured AMF colonization and communities in soybean roots, soybean growth parameters such as aboveground plant biomass, P uptake at the flowering stage and grain yields at the maturity stage in both years. The increase in the root colonization at the flowering stage was small as a result of P-application. Cover cropping did not affect the aboveground biomass and P uptake of soybean in both years, but the P-application had positive effects on the soybean performance such as plant P uptake, biomass and grain yield in 2015. AMF communities colonizing soybean roots were also significantly influenced by P-application throughout the 2 years. Moreover, the diversity of AMF communities in roots was significantly influenced by P-application and cover cropping in both years, and was positively correlated with the soybean biomass, P uptake and grain yield throughout the two years. Our results indicated that P-application rather than cover cropping may be a key factor for improving soybean growth performance with respect to AMF diversity in P-limited cover cropping systems. Additionally, AMF diversity in roots can potentially contribute to soybean P nutrition even in the P-fertilized cover crop rotational system. References

- Higo M, Isobe K, Drijber RA, Kondo K, Yamaguchi M, Takeyama S, Suzuki Y, Niijima D, Matsuda Y, Ishii R, Torigoe Y (2014) Impact of a 5-year winter cover crop rotational system on the molecular diversity of arbuscular mycorrhizal fungi colonizing roots of subsequent soybean. Biology and Fertility of Soils 50:913–926.

- Higo M, Isobe K, Kondo T, Yamaguchi M, Takeyama S, Drijber RA, Torigoe Y (2015) Temporal variation of the molecular diversity of arbuscular mycorrhizal communities in three different winter cover crop rotational systems. Biology and Fertility of Soils 51:21–32.

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Impacts of preceding cover crop residue management on the arbuscular mycorrhizal fungal communities, P nutrition and grain yield of maize Kento Gunji1, Masao Higo2,Yuya Tatewaki1, Yoshihiro Kawamura1, Katsunori Isobe2

1Graduate School of Bioresource Sciences, Nihon University, Kameino 1866, Kanagawa 252-0880, Japan.

2College of Bioresource Sciences, Nihon University, Kameino 1866, Kanagawa 252-0880, Japan.

Keywords: arbuscular mycorrhizal fungi, cover crop residue, phosphorus The introduction of winter cover crops has been shown to increase nutrient uptake and yield of subsequent crops (Isobe et al., 2014), and may result from increased AMF colonization in the roots. However, there is little information about the effects of different cover crops and AMF communities in roots and soil on the growth of subsequent crops. Thus, we evaluated the effects of the different cover crop residues on the AMF communities, P nutrition and yield of maize. A field experiment of a cover crop-maize rotational system was initiated at the experimental field of Nihon University, in Kanagawa, Japan from October, 2015. For the preceding cover crop, three winter cover crops; winter wheat, hairy vetch, and brown mustard were prepared with or without incorporation of cover crop residue.The colonization rate and community structure of AMF in maize roots, maize growth parameters such as plant biomass, P uptake at the V6 stage and grain yields at the maturity stage were investigated.The P uptake and plant biomass at the V6 stage and grain yield at the maturity stage differed among the cover crop. The colonization rate in the maize root was not significantly differenced by cover crop treatments. Although the AMF communities colonizing maize roots were not influenced by different of cover crop residue management, with or without incorporation the AMF communities were significantly changed by different of cover crops wheat, vetch and mustard.Our results indicated that cover cropping rather than incorporation of cover crop residue may be a key factor for shaping the AMF communities in maize roots. Table 1: Impacts of cover crop residue management on the arbuscular mycorrhizal fungal colonization, upground dry weight and P uptake of maize.

References: Isobe K, Higo M, Kondo T, Sato N, Takeyama S, Torigoe Y (2014) Effect of winter crop species on arbuscular mycorrhizal fungal colonization and subsequent soybean yields. Plant Production Science 17:260–267.

With 17.1 (±0.48)1) ab2) 81.0 (11.1) a 0.25 (0.05) a

Without 15.2 (±0.84) abc 51.8 (6.6) a 0.17 (0.03) a

With 18.2 (±0.63) a 71.1 (5.5) a 0.29 (0.03) a

Without 17.5 (±0.79) ab 68.1 (12.1) a 0.23 (0.05) a

With 14.1 (±0.85) b 63.6 (2.6) a 0.24 (0.01) a

Without 13.6 (±0.45) c 66.2 (15.8) a 0.22 (0.06) a

1) Each value is the mean (±SE).

2) Values followed by different letters within each cover crop significant different at P =0.05 by the Tukey test.

Treatment Cover crop residue AMF root colonization(%)

n.s.

n.s. n.s. n.s.

n.s. n.s. n.s.

n.s.3) n.s.

3) n.s.,no significant difference ,between with and without incorporation by t -test,respectively.

Plant biomass(g/㎡) P uptake(g/㎡)

Wheat

Vetch

Mustard

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Phosphorus fertilizer did not fully compensate reduction of crop yield on previously P depleted loamy sand soil in a long-term trial in

Germany Elkamu Jate, Christoph Steiner, Joachim Lammel, and Anke Kwast

Research Centre Hanninghof, Yara International, Hanninghof, Duelmen, Germany

Keywords: P fertilizer, soil P content, crop yield. This research comprises pot and field trials on phosphorus (P) uptake and yields of

crops grown on loamy sand soil at the Yara-Hanninghof long-term trial located near

Duelmen in northwestern Germany. This long-term experiment since 1958 with and

without application of P fertilizer resulted in the development of plots with different

soil P content. According to German classification, plant available soil P content at 0

– 30 cm depth (mg P2O5/kg soil) is categorised into very low (≤ 5.4), low (5.5 – 9.5),

medium (9.6 – 20.4), high (20.5 – 34.4), and very high (≥ 34.5).

The objective of the experiments was to investigate whether a sufficient P fertilizer

application can compensate for the differences in soil P supply. Therefore, the P

uptake and yields of crops, grown on the same field but on plots with different P

contents, were compared at the same P fertilizer rates. In pot experiments we

assessed 7 cuttings of rye grass and 7 cycles of spinach. In field trial, the crops

cultivated from 2009 to 2016 were silage maize, winter rye, and potato. The P

fertilizer (triple superphosphate, TSP) was applied at rates of 0%, 50%, 100%, and

200% of P removed by the crops in the pot trial. In the field, on average 33, 28, and

27 kg P per ha per year was applied in the form of TSP plus cattle slurry for silage

maize, winter rye, and potato cultivation respectively. The trial was established as a

randomized complete block design with 4 replicates.

At the highest P fertilization level (200%), there was on average a 2.4% reduction of

rye grass and a 12.6% (p < 0.05) reduction of spinach shoot dry matter yields on plots

with the medium P content compared to yields on the plots with a high P content.

The spinach yield on soil with low P content was on average 9.5% (p < 0.05) lower

than the yield on soil with medium P content. Similar results have been obtained in

the field where only a soil with high P and very high P content was available for the

experiment. Compared to crop yields on the plots with a very high P content, the

average crop yields on the plots with high P content were reduced by 9.3%(p < 0.05),

4%, and 20.5% (p < 0.05) for silage maize (n = 4 years), rye (n = 3 years), and potato

(n = 1 year) respectively. In economic terms it caused a revenue loss of 238, 57, and

1787 USD per ha per year for silage maize, rye, and potato respectively. Therefore,

it is important to maintain the P content of loamy sand soil in order to sustain high

crop production.

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Effect of P fertilization on arbuscular mycorrhizal communities and maize growth under a tilled and no-tilled system

Yuya Tatewaki1, Masao Higo2, Kento Gunji1, Yoshihiro Kawamura1, Katsunori Isobe2 1Graduate School of Bioresource Sciences, Nihon University, Kameino 1866,

Kanagawa 252-0880, Japan. 2College of Bioresource Sciences, Nihon University, Kameino 1866,

Kanagawa 252-0880, Japan.

Keywords: arbuscular mycorrhizal fungi, maize, phosphorus Utilizing the function of arbuscular mycorrhizal fungi (AMF) is important for optimizing their role for phosphorus (P) nutrition of maize under different tillage systems. However, it is not clear how maize growth and P nutrition is related to AMF root colonization and diversity of AMF communities under tilled or no-tilled systems (Jansa et al., 2003). Thus, we investigated the effects of P-fertilization and tillage systems on the interaction among AMF root colonization, AMF diversity in soil and maize roots, maize growth and P nutrition in no-tilled and tilled managements. In this study, we established two tillage systems (tilled and no-tilled) in maize cultivation field. The P-fertilization rates before the seeding of maize were 0 and 300 kg ha−1 .The colonization rate and community structure of AMF in maize roots and soil, plant biomass, and P uptake at the V8 stage were investigated. Regardless of tillage management, AMF root colonization at the V8 stage decreased only slightly as a result of P-fertilization. Additionally, both no-tillage and tillage management did not affect the plant biomass and P uptake of maize, but the P-fertilization had positive effects on the plant P uptake and plant biomass. Although the AMF communities in soil significantly differed between tilled and no-tilled plots, the AMF communities in roots were not influenced by P-fertilization and tillage. Our results indicated that tillage management rather than P-fertilization may be a key factor for shaping AMF communities in soil. However, the AMF communities in maize root were not mediated by the tillage management regardless of P-fertilization. Table 1: Effect of P fertilization on AMF root colonization, plant biomass and P uptake under tilled and no-tilled system.

References - Jansa J, Mozafar A, Khun G, Anken T, Ruh R, Sanders I R, Frossard E (2003) Soil tillage affects the community structure of mycorrhizal fungi in maize roots. Ecological Application 13:1164–1176.

No Tilled 16.1 (±3.5)1) a2) 25.3 (±5.4) ab 0.11 (±0.02) ab 0.66 (±0.14) ab

P-fertilization No-tilled 13.2 (±1.9) a 15.8 (±0.9) b 0.06 (±0.07) b 0.39 (±0.03) b

Tilled 18.2 (±2.5) a 34.6 (±3.3) a 0.16 (±0.04) a 0.85 (±0.07) a

No-tilled 13.8 (±2.5) a 26.9 (±2.0) ab 0.11 (±0.07) ab 0.62 (±0.05) ab

2) Values in a column followed by different letters are significantly different at P<0.05.

1) Each value is the mean (±SE).

AMF root colonization (%) P uptake of leaf (g/m²) P uptake of stem (g/m²)P fertilization Tillage systems

P-fertilization

Plant biomass (g/Plant)

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Effect of phosphorus (P) and manganese (Mn) supplies on root exudates of barley growing under acidic conditions

Rayen Millaleo1, Maria de la Luz Mora1 1Center of Plant, Soil Interaction and Natural Resources Biotechnology, Scientific and

Technological Bioresource Nucleus (BIOREN-UFRO), Universidad de La Frontera, P.O. Box 54-D, 01145 Fco. Salazar Av,Temuco, Chile.

Keywords: Organic acids, P supplies, manganese, barley Phosphorus (P) is an important macronutrient in plants, where is involve in vital processes of plant cell. However, in acid soils, P is not available for crops, due to high adsorption capacity in this soil, forming insoluble complexes with others minerals, causing P deficiency in plants. Likewise, manganese (Mn) excess is other feature that can produce damage to plants. Both P deficiency and Mn excess are present under acidic conditions, in cereal crops, with unclear physiological and/or biochemical responses even at the same species. Specifically, root exudates such as organic acids are adaptive mechanisms facing these acidic environments. Therefore, the objective of this work was to evaluate effects of P and Mn supplies on organic acids anions exudation in two barley cultivars, growing under acidic conditions. Barley differing in Mn resistance (Tatoo, Mn-tolerant and Scarlett, Mn-sensitive) were located in nutrient solution (pH 4.8), with P deficiency (16 µM) or normal (100 µM) P doses and Mn treatments during 10 days. Results showed that oxalate exudation was greater than citrate exudation in all P and Mn treatments, where Scarlett had higher oxalate exudation under P deficiency. Citrate exudation also was greater in Scarlett, in almost Mn treatments. Instead, Tatoo showed major citrate exudation with adequate P doses compared to P deficiency in all Mn treatments, suggesting different adaptive strategies between barley cultivars.

Figure 1: Organic compounds exuded by roots of barley, growing in acidic conditions with P deficiency (-P) and P adequate (+P) doses and Mn doses at 10 days. Different lowercase letters indicate statistically

significant differences

between P supplies for same Mn dose (Tukey´s test, P ≤ 0.05).

References - Rosas A, Rengel Z, Ribera A, Mora M (2011) Phosphorus nutrition alleviates manganese toxicity in Lolium perenne and Trifolium repens. Journal of Plant Nutrition and Soil Science 174:210-219.

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Does a high easily available P content negatively affect microbial biomass and activity in the rhizosphere?

Koen Willekens1, Thijs Vanden Nest1, Jane Debode1, Bart Vandecasteele1, Benny De Cauwer2, Nina Biesemans2, Lieven Delanote3, Karel Dewaele3

1Institute for Agricultural and Fisheries Research (ILVO), Burg. Van Gansberghelaan 109, 9820 Merelbeke, Belgium.

²Ghent University, Faculty of Bioscience Engineering, Department of Plants and Crops ³Inagro, Department of Organic Production

Keywords: Soil P status, symbiotic microbial activity, organic vegetable production The majority of the Flanders' agricultural soils shows a too high P-status due to historical excessively high P input. Chemical and biological soil quality status and weed pressure by Galinsoga species was evaluated for 50 certified organic vegetable fields over Flanders. Investigated chemical soil parameters were plant available nutrients (ammonium lactate extraction), pH-KCl, total organic carbon and nitrogen, sand fraction, hot water extractable carbon (HWC) and phosphorus (HWP). The latter is a measure for easily available P. Pedohydrological characteristics were recorded from the soil map of the Flemish region. Soil biology was examined by (i) phospholipid fatty acids extraction for quantification of total microbial biomass and specific functional groups (e.g., bacteria, fungi, mycorrhizae (AM fungi), …) and (ii) pH, Eh and EC measurements in soil extracts before and after a 24h incubation at 27°C (Husson 2013; Vanhoof 2014). This bio-electronic measurements allow to differentiate between activity of decomposer organisms in the bulk soil and microbial activity in the rhizosphere. The difference between EC values in soil extracts after incubation with and without an addition of sugars (EC27°C+S - EC27°C) is a measure of the activity of rhizosphere micro-organisms. Pearson correlation coefficients were calculated and tested for significance (p<0.05). A multivariate data analysis was performed by principal component analysis (PCA). Total microbial biomass and AM fungi were negatively correlated with HWP. 'EC27°C+S - EC27°C' was also significantly negatively correlated with HWP. These negative relations between rhizosphere microbiology and easily available P were also perceived in the PCA biplot (Fig. 1). An increasing amount of easily available P as a result of a high soil P status (P-AL range: 74-1138 mg P.kg-1 dry soil), seems to counteract microbial activity in the rhizosphere. In particular, organic growers rely on this microbial activity in the rhizosphere as a plant feeding mechanism. Therefore, fertilization strategy should aim at preventing P surpluses. References - Husson O (2013) Redox potential (Eh) and pH as drivers of soil/plant/microorganism systems: a transdisciplinary overview pointing to integrative opportunities for agronomy. Plant and Soil 362:389-417. - Vanhoof P (2014) Bodem Vitaliteitstest, www.organic-forest.eu/NL_BVV_test

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Figure 1: Biplot of the first two principal components of a PCA covering 66% of the variance and representing relationships between investigated soil parameters.

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Plant induced hydrolysis of polyphosphate fertilizer Ran Erel1, Qianqian Li1

1 Gilat Research Center, Agricultural Research Organization, M.P. Negev, 85280. Israel

Keywords: Polyphosphate, foliar fertilization In many agro-systems, P utilization efficiency is extremely low; roughly 20-30% of the applied P fertilizer is being recovered by crops. The main reason is fast adsorption-fixation reactions occurs in many soils. Polyphosphate (PP) fertilizers were suggested to lessen precipitation reactions as PP-hydrolysis is prerequisite. To understand factors governing PP hydrolysis and availability we initiated a series of controlled trials. At first stage, we tested the response of lettuce plants to soil and foliar application of PP. Surprisingly, we found P uptake of PP fertilizer sprayed directly to the shoot was as efficient as P-fertilizers based on orthophosphate. To best of our knowledge, leaf PP permeability is very low and thus, direct PP acquisition is unexpected. Hence, we hypothesis that initial hydrolysis is required. To better understand how PP is being acquired, we tested PP hydrolysis and uptake rate in aqueous solution in the present of leaf disks, leaf extracts, roots and detached roots. In two independent trials, foliar application of PP to lettuce deficient plants resulted in significant increase in plant biomass and P uptake. PP was as effective as conventional orthophosphate fertilizers, indicating significant shoot acquisition of P origin from PP based fertilizer. PP solution contained 50 mg/l P was incubated for 40 hr. in the presence of 2 gr of fresh leaf discs, leaf extract and leaf extract after heat treatment (boiled). In the control (untreated), PP hydrolysis was insignificant while in the leaf discs treatment we found that all PP was hydrolyzed within 40 hr. In PP solution with leaf extracts, 29 and 67% of the PP was hydrolyzed in the boiled and fresh extracts respectively. In related setup, we tested the effect of active (hydroponic) and detached roots on PP hydrolysis. Hydrolysis rate was highest in the present of active roots and significantly higher in the presence of roots compare to untreated control. Our results indicates that PP hydrolysis rate is strongly influenced by the presence of plants organs. The enhancement effect is related to enzymatic non-enzymatic reactions. Since plants induce PP hydrolysis, the relevance of soil incubation test is questionable. If plants indeed promote rapid PP hydrolysis in their natural environment then stable PP fertilizers may have benefit over orthophosphate based fertilizers. PP fertilizer may serve as "P capsules" waiting for root interaction to release P

Figure 1: Percentage of polyphosphate hydrolysis is aqueous solution containing 50 ppm P

020406080

100

Control Boiled leafextract

Fresh leafextract

Fresh leafdiscsP

oly

ph

osp

hat

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ydro

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Optimum level of soil available phosphorus for AMF inoculation to Welsh onion in non-allophanic Andosol

Takae Suzuki1, Toru Uno1, Ryosuke Tajima1, Toyoaki Ito1, Masanori Saito1,2 1Graduate School of Agricultural Science, Tohoku University, Naruko-Onsen, Osaki, Miyagi 989-

6711, Japan. 2Japan Science and Technology Agency, Goban-cho, Chiyoda, Tokyo 102-0076, Japan.

Keywords: AM fungi, Available phosphate, Andosol

It was demonstrated that inoculation of arbuscular mycorrhizal fungi (AMF) to Welsh onion (Allium fistulosum L.) was effective to improve its growth and to reduce phosphorus (P) fertilizer (Tawaraya et al., 2012). Non-allophanic Andosol is a volcanic soil with high P fixing capacity, so application of AMF is expected for efficient use of P fertilizer. However, it is not yet clarified what level of soil available P is suitable for effective AMF inoculation in non-allophanic Andosols (Suzuki et al. 2015). To clarify the optimum level of soil available P in a non-allophanic Andosol, we conducted field experiments of Welsh onion for 4 years in Field Science Center of Tohoku University, Japan. Welsh Onion was inoculated with a commercial inoculum containing Glomus sp. R10 and grown for about 8 weeks in nursery bed in greenhouse. The seedlings were transplanted to the plots with different levels of soil available P due to previous fertilization. Soil available P of the plots were Very high (VH), High (H), Medium (M), and Low (L). The AMF inoculation significantly increased the yields in the M and H plots, while no effect was found in the VH plot. In the L plot, plant growth was so poor that the inoculation did not clearly improve

yields. Additional P fertilizer was applied upon

transplanting, but this P fertilization did not much affect the yield of Welsh onion. These results indicate that a medium to high level

of soil available P is needed to increase effectiveness of

AMF inoculation to Welsh onion in the non-

allophanic Andosol.

References - Tawaraya et al. (2012) Inoculation of arbuscular mycorrhizal fungi can substantially reduce phosphate fertilizer application to Allium fistulosum L. and achieve marketable yield under field condition Biol. Fertil. Soils, 48: 839−843.

- Suzuki et al. (2015) Effect of arbuscular mycorrhizal fungal inoculation on the growth of Welsh onion in soil rich in available phosphate, and characterization of indigenous arbuscular mycorrhizal fungi isolated from the soil. Soil Microorganisms, 69: 48-57.

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Soil protist communities as influenced by long-term management and applied phosphorus source

Tandra D. Fraser1, Kari E. Dunfield2, Martin H. Entz3, Derek H. Lynch4 1Charlottetown Research and Development Centre, Agriculture and Agri-Food Canada,

Charlottetown, PE, Canada 2School of Environmental Sciences, University of Guelph, Guelph, ON, Canada 3Department of Plant Science, University of Manitoba, Winnipeg, MB, Canada

4Department of Plant, Food and Environmental Sciences, Dalhousie University, Truro, NS, Canada

Keywords: Soil protists, mineral P, manure P Protists are key players in soil biological communities, with the potential to accelerate phosphorus turnover through microbial grazing. However, the structure of protist communities in soils is largely unknown, especially considering the effects of long-term management and nutrient additions. Although Cercozoa have been found to represent a dominant group of heterotrophic free-living protists that may play an important functional role in nutrient cycling, the specific functions and the factors affecting diversity remain mostly undescribed. The aim of this study was to examine cercozoan communities in soils collected from a 20 y trial in Manitoba, Canada under no input (NI), conventional (CONV) and restored prairie (PRA) management systems in relation to P bioavailability, plant growth and P uptake. Italian ryegrass (Lolium multiflorum) seedlings were grown in the greenhouse in soils amended with manure P or mineral P compared to a control (no P added) and sampled at 30 and 106 days after planting. The DNA was extracted from soils at 30 d only and the Cercozoan communities assessed using specific PCR primers targeting the 18S hypervariable V4 region (S616F_Eocer, S616F_Cerco, S963R_Cerco; Fiore-Donno et al. 2017). Next generation sequencing of the amplicons is being completed using the Ion Torrent Personal Genome Machine. Preliminary results indicate that the NI soil had lower concentrations of resin-P and NaHCO3-P compared to the CONV and PRA soils prior to planting and at harvest. The effect of different management systems and P amendment on cercozoan diversity in relation to soil bioavailable P will be presented. Future analysis will need to validate the functional role that protist diversity plays in P bioavailability. References - Fiore-Donno AM, Rixen C, Rippin M, Glaser K, Samolov E, Karsten U, Becker B, Bonkowski M (2017) New barcoded primers for efficient retrieval of cercozoan sequences in high-throughput environmental diversity surveys, with emphasis on worldwide biological crusts. Mol Ecol Resour 18: 229-239.

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Root phosphorus release through rhizodeposits and its fate in the rhizosphere Martin Schneider, Alireza Golestani Fard, Hans-Peter Kaul, Jakob Santner

Division of Agronomy, University of Natural Resources and Life Sciences, Konrad-Lorenz-Straße 24, 3430 Tulln an der Donau, Austria

Keywords: root border cells, DGT, chemical imaging Numerous preceding studies present the root tip as a hotspot of high P concentrations in the external soil solution. In addition to the high biological activity at the tips, and therefore potential P mineralization from soil organic matter, rhizodeposits (root border cells, dead root cells, mucilage and exudates) are a potential source of external solution P. Interestingly, rhizodeposits are intensively studied for C and N, but not for P release. The present study aimed at localizing P release through rhizodeposits by soil-grown plant roots, as well as studying P release from isolated rhizodeposits incubated in soil. The experimental plants (bean, maize and sunflower) were grown in rhizotrons, which allow direct access to soil-grown roots for sampling deposited 33P. The plant shoot was radiolabeled with 33P through a small lesion in the coleoptile, after 2 weeks of growth. Chemical imaging of root-released 33P was performed by application of zirconium oxide-impregnated, P-binding hydrogels onto the roots system, with subsequent imaging of the sampled 33P using autoradiography. In a second experiment, the experimental plants were grown in drop-less mist culture (aeroponics) for 3 weeks, and radiolabeled in the same way. Radiolabeled rhizodeposits were harvested from these roots and used for studying the release of P during their incubation in soil. Chemical imaging of released P during the 24 h hydrogel deployment showed highly localized release of 33P at root tips of either primary, basal and lateral roots, with small amounts also released along the root axes. The mineralization study of rhizodeposits is still in progress.

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Influence of root characteristics on phosphorous uptake under alkaline conditions

1 Sara Halicki, 2 Bahar S. Razavi, 1,3Mutez Ahmed, 1Frederick Asankoma 1 Michaela A. Dippold 1Department of Agricultural Soil Science, Georg-August-University of Gottingen, Germany

2 Department of Soil Science, Christian-Albrecht-University of Kiel, Germany 3Department of Soil Physics, University of Bayreuth, Germany

Keywords: Mineral phosphorous uptake, 33P Imaging, pH Optode, rhizosphere acidification Root morphology has a strong impact on plants ability to penetrate the soil and to reach a larger soil area and thus essential nutrients as phosphorous (P). Therefore, plants can develop different root types and various amounts of root hairs. As P is less mobile in soil solution than other nutrients, specific root traits are crucial to ensure an optimum supply. Besides the optimum proximity of roots to P molecules in soil, plants often influence the chemical properties to convert chemical unavailable to available P forms. The capability to mobilize P under alkaline soil conditions (pH 8.3 in water) was tested in this study with two varieties of maize and barley with and without root hairs, respectively. Each treatment was replicated four times. The study was conducted in the climate chamber under controlled temperature and light conditions. The plants were grown in 10 x 19 x 1.5 cm rhizoboxes filled with 500 g dry soil and saturated to 100% field capacity. To prove if maize and barley acidify the rhizosphere to mobilize P from the mineral soil fraction, two methods were combined. First, the soil was labelled with a small amount of 33P with an activity of 2 MBq per rhizobox to trace the P mobilization from the soil to the plant. Second, soil and rhizosphere pH was measured in situ with pH Optode sensors. Maize and barley were able to acidify the rhizosphere from 8.3 to 7.5 in average. The pH change was strongest at the young roots parts, but not directly at the root tips pointing towards the fact that a certain accumulation of organic acids is required until a significant decrease in this strongly buffering soil could be observed. In maize, specifically crown roots strongly decrease the rhizosphere pH. However, especially at early growth stages spatial correlation between rhizosphere acidification and P uptake is rather low suggesting additional mechanisms contributing to the high P uptake e.g. at root tips.

Figure 1: Barely with root hairs;

P Imaging (left) and pH (right

Figure 2: Maize with root hair

(pH))

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Gene co-expression analysis and modeling reveal distinct regulatory networks for phosphate homeostasis in mycorrhizal plants under phosphate deficiency Hayato Maruyama1, Yusaku Sugimura1, Ayumi Tezuka2, Atushi J. Nagano2, Tatsuhiro Ezawa1

1Graduate School of Agriculture, Hokkaido Univ., 060-8589, Sapporo, Japan. 2 Faculty of Agriculture, Ryukoku Univ., 520-2194, Ohtsu, Japan.

Keywords: Co-expression modules, Mycorrhizal plants, Phosphate homeostasis Arbuscular mycorrhizal (AM) fungi play a predominant role in phosphate (Pi) acquisition of most land plants through providing the mycorrhizal pathway in addition to the root direct pathway. Although the Pi-signaling pathway in the model plant Arabidopsis that has only the root direct pathway has extensively been studied, information about the molecular networks regulating Pi homeostasis in mycorrhizal plants is limited. Our aim is to understand the regulatory networks for the acquisition of Pi through the mycorrhizal and root direct pathways in terms of the maintenance of Pi homeostasis in mycorrhizal plants. A mycorrhizal model plant Nicotiana benthamiana was inoculated with Rhizophagus clarus HR1 and grown in the two-compartment culture system. Nutrient solution was applied either to the root compartment of non-mycorrhizal plants (root direct pathway, RDP) or to the hyphal compartment of mycorrhizal plants (mycorrhizal pathway, MP). Total RNA was extracted from the roots 6 weeks after inoculation, and single-end 50-bp sequencings were performed with Illumina HiSeq. Gene-expression data were obtained from 125 samples and subjected to co-expression gene network analysis with respect to Pi status and also to LASSO modeling for constructing a molecular marker to estimate amounts of Pi taken up through the MP and RDP. Composition of genes in the modules to which PHR1, the master regulator of Pi-responsive genes, belongs was different between the mycorrhizal and non-mycorrhizal plants. Genes involved in Pi homeostasis, e.g., those encoding SPX-domain containing protein, differently responded to external Pi concentration in the mycorrhizal and non-mycorrhizal plants. A molecular marker consisted of 8 root-expressed genes enabled to estimate the amounts of Pi taken up through the MP and RDP; correlation coefficients between actual values and estimated values were 0.97 and 0.95 for the MP and RDP, respectively. The marker illustrated that a large fraction of Pi was taken up through the MP in the mycorrhizal plants, confirming that mycorrhizal formation drastically modifies regulatory networks for Pi acquisition, which results in the large shift in Pi uptake pathway from the RDP to the MP. Our modeling also presents the technical feasibility for estimating relative contribution of the two Pi-uptake pathways in mycorrhizal plants, which opens a new window for the evaluation of the significance of MP in the field.

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Phosphorus efficient cultivars for increasing peanut productivity in India A.L Singh

ICAR-Directorate of Groundnut Research, PB 5, Junagadh 362001, India

Keywords: P-efficient, peanut cultivars Peanut is an important food legume of semiarid tropical world mainly grown in light textured soils, where phosphorus (P) deficiency is one of the most limiting factors affecting its growth, and N2-fixation (Singh et al 2015). However, being a P-efficient crop, the response of peanut to P depends greatly on the soil P and genotypes (Singh and Basu 2005). India has released nearly 200 peanut cultivars and hence, it is most pertinent to identify and make use of P-efficient cultivars by resource poor farmers to harvest reasonable yield. In this series, 100 peanut cultivars, were evaluated for their yield attributes and seed P concentrations, in field under P-deficit and adequate-P condition for two consecutive years, under P-unfertilized (UF) and P-fertilized (50 kg P ha-1) conditions in a soil having low available phosphorus (6-7 ppm P), 7.6 pH, 0.70 % organic C and 570 ppm N. The cultivars were categorized as P-efficient when their yields were more than population mean plus standard deviation (SD) and the one having pod yield less than population mean minus SD as P-inefficient (Singh et al 2015). Application of P increased yield and seed P concentration with huge differences in pod yield, but small differences in seed P among 100 peanut cultivars, with more pronounced effect on pod yield which was identified as selection criterion for P-efficient cultivars. The average and range of pod yields were 165 and 59-276 g m-2 under UF which increased to 171 and 66-292 g m-2, respectively with 50 kg P. Out of 100 cultivars, 21 and 22 cultivars under UF and F, respectively, with >200 g m-2 pod yield were P-efficient. On the other hand 15 cultivars with <130 g m-2 pod yield under both F and UF were P-inefficient. However nearly 30 cultivars did not respond to P application. Based on the overall performance following cultivars were identified as: - P-efficient: GG 5, ICGS 1, RG 141, TMV 2, Tirupati 2, Tirupati 4, ICGV 86031 and 86590, GG 3, ICGS 37 and 44, GG 7, SB XI and JL 220 (>200 g m-2 pod yield) - P-inefficient: TKG 19 A, GAUG 10, RS1, RS 138, ALR 1, Chico, MH 2, MH 4, T 64 R 8808 and Gangapuri (<130 g m-2 pod yield). The P-efficient peanut cultivars having superior yield under both P-fertitized an P-unfertilized conditions are of practical significance and farmers are recommended to grow them to reduce the P fertilizer and maintain P resources. References - Singh AL and Basu M.S. (2005) Screening and selection of P efficient genotypes for calcareous soils in India. Proc XV IPNC “Plant nutrition for food security, human health and environmental protection. Beijing, pp 1004-1005. - Singh AL, Vidya Chaudhari, Ajay BC (2015). Screening of groundnut genotypes for phosphorus efficiency under field conditions. Indian J Genetics 75: 363-371.

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Evaluation of the effect of soil organic phosphorus on the phosphorus acquisition of rice genotypes Erina Shimamura1, Erik Smolders1

1Division of soil and water management, KU Leuven, Kasteelpark Arenberg 20, 3001 Leuven, Belgium

Keywords: Rice genotype, phosphorus acquisition efficiency, organic phosphorus Breeding of rice varieties with high phosphorus (P) acquisition efficiency (i.e. P uptake at low P availability) has been constrained by the difficulty of identifying responsible root traits for existing genotypic variation (Vandamme et al., 2016). Organic P constitutes a large part of the P pool in tropical soils, offering the potential P source for rice production in low-input systems (Turner, 2006). It is well established that plant roots can mobilize P in the rhizosphere; yet, little is known about the contribution of organic P to the P uptake of rice plants. The goal of this study is to test if rice genotypic variation in P acquisition efficiency can be explained by plant capacity to access soil organic P fractions. Six upland rice varieties were grown for 21 days to compare growth response under increasing organic P content during vegetative stage. Three mixtures (substrates) of inorganic and organic soils i.e. ferralsol mixed with peat soil at 0, 50 and 100% ratio were used to give 3 levels of organic P supply, and each combined with 3 application rates of KH2PO4 to give the final P concentration of < 0.03, 0.1, and 1 mg P/L by 0.01M CaCl2 extraction. All substrates were adjusted to pH 4.5. The CaCl2 extraction of these substrates confirmed that the organic P fractions were 28-100% (100% ferralsol), 35-97% (50/50% ferralsol and peat soil), and 62-65% (100% peat soil) at medium to low P treatments. Overall, shoot biomass and P uptake of rice plants increased by P application in all substrates, and bigger root biomass was observed in more organic substrates. There was genotypic variation in shoot P uptake and root efficiency (i.e. total plant P uptake per root mass) at each P level (p < 0.01). Shoot P uptake and root efficiency ranged among genotype (2.34-3.62 mg and 12.16-19.15 mg/g), P level (0.80-4.88 mg and 5.11-30.99 mg/g), and substrate (2.59-3.11 mg and 13.30-19.57 mg/g). The variation in P uptake was largely explained by P level (81%), and root efficiency by both P level (56%) and P level-substrate interaction (13%). Genotype-substrate interaction only explained little of the variation in both shoot P uptake (0.8%) and root efficiency (4.8%). We conclude that there is a genotypic variation in P acquisition efficiency but the contribution of the difference in accessibility to soil organic P fraction is smaller than other factors. References - Vandamme E, Rose T, Saito K, Jeong K, Wissuwa M (2016) Integration of P acquisition efficiency, P utilization efficiency and low grain P concentrations into P-efficient rice genotypes for specific target environments. Nutr Cycl Agroecosyst 104:413-427. - Turner BL (2006) Organic phosphorus in Madagascan rice soils. Geoderma 136:279–288.

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Optimization of phosphorus availability in soil: impact of Phosphate-Solubilizing Microorganisms on rapeseed growth and nutrient use

efficiency. Charlotte Amy1,2, Mélanie Bressan2, Karine Laval2, Jean-Christophe Avice1

1 UMR INRA/UCN 950 Ecophysiologie Végétale et Agronomie (EVA), SFR Normandie-Végétal FED 4277, Université de Caen Normandie, Esplanade de la paix, F-14032 Caen, France

2UniLaSalle, unité de recherche AGHYLE, UP 2018.C101, SFR Normandie-Végétal FED 4277, 3 Rue du Tronquet - CS 40118, F-76134 Mont-Saint- Aignan, France

Keywords: Rapeseed, biofertilizers, nutrient use efficiency Phosphorus (P) is an essential element that is necessary for plant and soil microbial development and growth, but limiting because of its low availability and mobility in soil1. Phosphate, the only form that plants can absorb, is largely complexed in organomineral particles2. The pool of soil available P is mainly supplied from organic matter mineralization and dissolution of clay-P, Fe-P and Al-P complexes. Moreover, the majority of the applied inorganic P fertilizer in soil is not available to plants. This low availability is generally balanced by excessive addition of P fertilizers, leading to environmental problems3. Rapeseed, an oleoproteaginous crop of interest in France and Normandy, is characterized by high requirements in P and also nitrogen (N). This specific requirement is partially due to low nutrient use efficiency in this crop. During leaf senescence, incomplete proteolysis leads to low remobilization of endogenous nutrients. To promote access to poorly available nutrients, like P, rapeseed is likely to recruit soil microorganisms through root exudation4. These specific microorganisms called « PSM » (Phosphate-Solubilizing Microorganisms) can improve plant nutrition by increasing organic P mineralization or with efflux of molecules directly acting on complex P forms5. These microorganisms of interest represent a possible efficient alternative to mineral fertilization4. In this context, the aim of this work is to evaluate the agronomic effect of efficient biofertilizers composed of beneficial microorganisms on rapeseed growth. Besides agronomic performance, the objective is also to apprehend direct or indirect processes implicated in P and N uptake. More particularly, the impact of microbial consortium and individual PSM, isolated from rapeseed rhizosphere, will be evaluated on plant growth and microbial dynamics linked to P and N cycles. Indeed, known reciprocal synergy between P availability and N cycle functioning, little studied, and the strong link between P and N metabolisms highlights the interest to consider the nutritional interactions P x N to improve use efficiency of these two elements. References: 1. Vance, C. P. (2001) Symbiotic Nitrogen Fixation and Phosphorus Acquisition. Plant Nutrition in a World of Declining Renewable Resources. Plant Physiology 127, 390–397. 2. Koch, M. et al. (2018) Phosphorus stocks and speciation in soil profiles of a long-term fertilizer experiment: Evidence from sequential fractionation, P K -edge XANES, and 31 P NMR spectroscopy. Geoderma 316, 115–126. 3. Syers, J. ., Johnston, A. & Curtin, D. (2009) Efficiency of soil and fertilizer phosphorus use: reconciling changing concepts of soil phosphorus behaviour with agronomic information. Experimental Agriculture. 45, 128.

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Carbon and phosphorus allocation in crops : an optimization approach Marko Kvakić1,2, George Tzagkarakis3, Sylvain Pellerin1, Phillipe Ciais2, Daniel Goll2, Xuhui

Wang2, Bruno Ringeval1 1ISPA, Bordeaux Sciences Agro, INRA, 33140 Villenave d’Ornon, France

2LSCE/IPSL, CEA-CNRS-UVSQ, Universite Paris-Saclay, F-91191, Gif-sur-Yvette, France 3EONOS Investment Technologies, 10 Rue de Penthievre, 75008, Paris, France

Keywords: phosphorus, crops, limitation, carbon, allocation, optimality Inclusion of phosphorus (P) in vegetation models has been deemed crucial as nutrients exert strong control on plant development. Under P deficiency, plants invest more carbon (C) into roots and less into leaf, leading to lower photosynthesis and ultimately yield. Our proposed method models this effect using a resource optimization technique while following plant optimality principles: maximizing growth while respecting plant physiological needs [1]. More specifically, the model consists of several C and P pools: leaf, root, stem, fruit and a reserve. Only leaves and roots acquire C and P (respectively) which are then allocated to all organs in order to maximize plant growth, while respecting certain constraints: root-shoot ratio, stem-leaf ratio and minimum P concentration. The allocation process is optimized dynamically using linear programming and integrated to reproduce plant response at different P levels. Our model reproduces plant biomass and concentration change due to P availability as a result of C reallocation (Fig. 1). Our analysis suggests that C reallocation is the main process guiding plant development, while other ones are negligible (e.g. leaf P dependent assimilation). We also found that assumptions regarding maintenance respiration critically affect the simulated plant response. More precisely, we found that having a constant specific cost (linear respiration) cannot reproduce concentration change if plant optimality principles are invoked. Rather, a biomass dependent (increasing) specific cost is needed to reproduce tissue concentration change. In summary, our proposed approach offers a more transparent and parsimonious way to modelling nutrient effects in crops, with the final goal of introducing it into a global vegetation model and looking at P limitation in crops worldwide.

Figure 1: Crop response to P level at the end of the vegetative stage. kCR is the root P uptake rate and corresponds to P availability. Full and dashed lines represent the two respiration models. Colors depict different vegetative organs

References: [1] H.A. Mooney A. J. Bloom F.S. Chapin. “Resource Limitation in Plants-An Economic Analogy”. In: Annual Review of Ecology and Systematics 16.1 (1985), pp. 363–392.

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Transcriptional and post-transcriptional regulation of barley PHO2 gene

Pawel Sega1, Katarzyna Kruszka1, Wojciech Karlowski2, Zofia Szweykowska-Kulinska1, Andrzej Pacak1

1Department of Gene Expression, Institute of Molecular Biology and Biotechnology, Faculty of Biology, Adam Mickiewicz University in Poznan, Umultowska 89, 61-614 Poznan, Poland

2Department of Computational Biology, Institute of Molecular Biology and Biotechnology, Faculty of Biology, Adam Mickiewicz University in Poznan, Umultowska 89, 61-614 Poznan,

Poland

Keywords: barley, TF, gene expression PHO2 (PHOSPHATE2) encodes ubiquitin-conjugating (UBC) E2 enzyme involved in phosphate homeostasis maintenance. It was shown that PHO2 is involved in the degradation of Pi transporters, namely PHO1 (PHOSPHATE1) and PHT1 (PHOSPHATE TRANSPORTER1) family members in Arabidopsis thaliana. Based on the current state of art there is still lack of information about transcriptional regulation of PHO2 gene expression. Using in silico approach we have identified the presence of two P1BS motifs in 5’-UTR (1st intron and 2nd exon) of PHO2 gene in barley. Interestingly, these elements are not present in the PHO2 promoter region. We have found that the PHO2 gene region containing P1BS motifs can bind the following transcription factors: PHR1 (PHOSPHATE STARVATION RESPONSE1) and the newly identified and named by us TF PHRx. Further results confirmed the binding of PHRx, PHR1 to the 5’UTR of PHO2 gene using in vivo and in vitro approaches. Following in silico analysis we revealed that novel protein PHRx belongs to the MYB-CC transcription factors family and forms either homodimers or heterodimers with previously described TF PHR1. Our hypothesis is, that the complex of PHR1, PHRx proteins might be crucial for the PHO2 transcriptional activity during phosphate deficiency in plants. Moreover, we have found that PHRx directly interacts with SIZ1 protein which modifies the target protein through sumoylation process. It is highly probable that PHRx undergoes sumoylation upon SIZ1 interactions. PHO2 is also regulated post-transcriptionally via microRNAs. Analysis of PHO2 mRNA fragments generated upon Pi starvation through miR399 action revealed cleavage site no 5 as the most occupied. This work was funded by the National Science Centre, Poland based on the decision: DEC-2013/11/B/NZ9/01761, UMO-2016/23/B/NZ9/00857, UMO-2015/19/N/NZ9/00218, and supported by KNOW RNA Research Centre in Poznan 01/KNOW2/2014.

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Interactions of barley proteins involved in phosphate homeostasis maintenance

Maria Barciszewska-Pacak, Pawel Sega, Agata Stepien, Andrzej Pacak Department of Gene Expression, Institute of Molecular Biology and Biotechnology, Faculty of

Biology, Adam Mickiewicz University in Poznan, Umultowska 89, 61-614 Poznan, Poland.

Keywords: barley, phosphate, protein interactions

Phosphorus is a macronutrient available as an inorganic phosphate (Pi) anion for

plants. Insufficient Pi concentration in soil leads to lower barley weight and faster

senescence of leaf no 1. Additionally, we showed that Pi-related gene expressions

are mostly downregulated by heat stress. However, Pi concentrations are

maintained in barley roots and shoots during the stress. Barley plants seem to adjust

gene expressions and protein levels to keep the Pi concentration constant. We aim

to establish the Pi-related proteins network regulating Pi concentration during heat

stress in barley. We would like to find the proteins targeted by the so far confirmed

PHO2/NLA (PHOSPHATE2/Nitrogen Limitation Adaptation) complex, regulating Pi

homeostasis, and unravel regions involved in the interactions. It will allow us to

understand better how plants can adapt to unfavourable environmental conditions,

including heat stress. Förster Resonance Energy Transfer – Fluorescence-Lifetime

Imaging Microscopy (FRET-FLIM) has been chosen for verification of PHO2, NLA and

other Pi-related proteins interactions in barley. Using TOPO cloning and Gateway

technology by Invitrogen, different destination pSU3 and pSU5 vectors have been

prepared for barley protein cDNA N- and C-terminal fusions with Green Fluorescent

Protein (GFP) and Red Fluorescent Protein (RFP) tags. Barley cv. Morex protoplasts

have been used for isolation and transfection with the DNA transiently expressed

constructs and further analysed by FRET-FLIM. PHO2 fusion protein expression

occurred to be homogenous, cytoplasmic and also nuclear. NLA fusion protein was

expressed in cytoplasm less homogenously and in specific speckles there. The results

confirmed the binding of donor GFP-tagged NLA with acceptor RFP-tagged PHO2 by

the donor fluorescence lifetime changes in presence of acceptor protein (data

unpublished). We propose that the direct interactions between barley PHO2 and

NLA proteins influence Pi homeostasis maintenance during heat stress. Interactions

between barley PHO2, NLA and their potential partner proteins, like PHO1

(PHOSPHATE1) and Pi transporters PHT1, PHT2, PHT3, PHT4 will be further verified

by FRET-FLIM to understand the mechanisms of phosphate homeostasis

maintenance in crops during heat stress.

This work was funded by the National Science Centre, Poland, grant no UMO-

2016/23/B/NZ9/00857, UMO-2015/19/N/NZ9/00218 and supported by KNOW RNA

Research Centre in Poznan 01/KNOW2/2014.

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Characterization of proteins containing an EXS domain in Arabidopsis thaliana Yi-Fang Hsieh, Yves Poirier

Department of Plant Molecular Biology, University of Lausanne, Switzerland

Keywords: EXS domain, phosphate transport and homeostasis PHO1 (PHOSPHATE 1) is involved in phosphate (Pi) export from roots to shoots. The PHO1 protein contains the hydrophilic SPX (SYG1/Pho81/XPR1) domain at the N-terminus involved in binding inositol pyrophosphate, the hydrophobic EXS (ERD1/XPR1/SYG1) domain at the C-terminus and four transmembrane domains in between. Previous studies showed that the expression of the EXS domain of PHO1 alone in pho1 mutant could ameliorate shoot growth while the shoot phosphate level remained low (Wege et al., 2016). However, the mechanism behind this growth enhancement is unclear. The EXS domain in Arabidopsis thaliana has been identified in all members of the PHO1 family as well as in two other proteins, named ERD1A and ERD1B, that do not contain the SPX domain. A yeast homolog of these two proteins, ScERD1, was reported to be important for ER protein retention (Hardwick et al., 1990) and recycling of Pi byproducts from glycosylation in Golgi (Snyder et al., 2017). An Arabidopsis T-DNA mutant in the ERD1A gene shows stunted growth and reduced pollen fitness and/or viability, while the T-DNA mutant in the ERD1B gene has no significant phenotype. Using GUS reporter lines, we show that ERD1A and ERD1B are broadly expressed in various tissues, including vascular cylinder in roots and stamen, but the expression level of ERD1A is higher than ERD1B. Transient expression of ERD1A and ERD1B fused to florescent proteins in tobacco leaves indicate their localization to the Golgi. Moreover, to know if the EXS domains of PHO1 and ERD1A have similar function, we substituted the EXS domain of ERD1A with the EXS domain of PHO1. The latter chimera did not alleviate the erd1a mutant phenotype, implying that the EXS domain of ERD1A and PHO1 may have distinct roles. Further studies are required to explore the function of ERD1A and ERD1B regarding ER protein retention and phosphate transport and homeostasis along with the similarities and differences among the EXS domains of ERD1A, ERD1B and PHO1. References - Hardwick K, Lewis M, Semenza J, Dean N, Pelham H (1990) ERD1, a yeast gene required for the retention of luminal endoplasmic reticulum proteins, affects glycoprotein processing in the Golgi apparatus. EMBO J. 9:623–630. - Snyder N, Stefan C, Soroudi C, Kim A, Evangelista C, Cunningham (2017) H+ and Pi byproducts of glycosylation affect Ca2+ homeostasis and are retrieved from the Golgi complex by homologs of TMEM165 and XPR1. G3 7:3913-3924 - Wege S, Khan G, Jung J, Vogiatzaki E, Pradervand S, Aller I, Meyer A, Poirier Y (2016) The EXS domain of PHO1 participates in the response of shoots to phosphate deficiency via a root-to-shoot signal. Plant Physiology 170:385-400

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Identification of drugs altering phosphate homeostasis in plants Caroline Mercier1, Marie-Christine Thibaud1, Laura Cuyas2, Thierry Desnos1, Christian Godon1,

Pascale David1, Jean-Claude Yvin2, Sylvain Pluchon2, Laurent Nussaume1 1 Laboratoire de Biologie du Développement des Plantes, Institut de Biosciences et

Biotechnology Aix-Marseille, UMR 7265 CNRS-CEA-Aix Marseille Univ. Centre d’étude nucléaire de Cadarache, Saint-Paul-Lez-Durance 13108, France, 2 Plant Nutrition Department, Centre

Mondial de I'lnnovation Roullier, Saint-Malo 35400, France.

Keywords: Phosphorus nutrition, Arabidopsis, Chemical genomics, Phosphate Phosphorus is an essential macronutrient for all living organisms. Plants preferentially absorb phosphorus as orthophosphate (Pi), however its availability is limiting plant growth in a vast majority of soils. In order to ensure plant productivity in the fields, fertilizers are added to crops. Unfortunately, more than 80% of Pi supplied is not absorbed by plants and lost in the soils (by chelation, leaching…). The aim of this project is to induce Pi deficiency response in the plants to activate Pi uptake mechanisms by chemical genetics. This may provide solutions to reduce fertilizer losses and to optimize Pi absorption. We have proven success of this approach in the past by using chemical compound library (Arnaud et al., 2014; Bonnot et al., 2016). However, not knowing the impact of these compounds on environment, prompted us to look for natural substances that could offer sustainable alternative solutions. Therefore different collections have been screened

by the use of Arabidopsis thaliana seedlings harboring a reporter gene sensitive to Pi deficiency (SPX1). The promoter of this gene was fused to the ß-glucuronidase reporter gene. Arabidopsis seedlings harboring this construct were used to identify compounds affecting Pi response in plants. From a total of 10,055 molecules tested, 9 were selected as putative strong hits. These further analyses including Pi content, gene expression analyses or plant yield quantification has provided us clues of the possible applications of these drugs (e.g., stimulation of the expression of Pi starvation transporters). Additional experiments will be required in order to analyze other possible symptoms of Pi homeostasis impairment in Arabidopsis as well as try to transfer the results obtained to plant crops.

Figure 1: Transgenic Arabidopsis lines exhibiting reporter gene sensitive to Pi deficiency. References - Arnaud, C. et al. (2014). Identification of phosphatin, a drug alleviating phosphate starvation responses in

Arabidopsis. Plant Physiol 166: 1479-1491.

- Bonnot, C., et al. (2016). A chemical genetic strategy identify the PHOSTIN, a synthetic molecule that triggers phosphate starvation responses in Arabidopsis thaliana. The New phytologist 209: 161-176.

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Beech and poplar show contrasting P nutrition strategies during annual growth Cornelia Herschbach

Chair of Ecosystem Physiology, Institute for Forest Sciences, Albert-Ludwigs-University Freiburg, Georges-Köhler-Allee 53/54, 79110 Freiburg, Germany.

Keywords: European beech, Poplar, P-nutrition strategy Phosphorus (P) constitutes one of six macronutrients essential for plant growth and development due to the central function of phosphate (Pi) in energy metabolism, inheritance and metabolic control. In many ecosystems, plant available P in the soil gets limited by soil aging. Plants established on P-poor soils developed adaptation strategies to cope with such limitation by several processes. At the ecosystem level it is assumed that the strategy of ecosystem P nutrition depends on soil type and the progress of pedogenesis (Lang et al., 2016). At the example of temperate beech forests, it is further hypothesized that ecosystems established on P-rich soils can be characterize as P-acquiring ecosystems, whereas forests established on P-poor soils represent P-recycling ecosystems. Fagus sylvatica trees growing in forests on P-limited soils require an efficient P-nutrition strategy to sustain sufficient P for growth and development. In contrast, the natural floodplain habitat of fast-growing Populus x canescens is characterized by high soil-P availability. Consequently, the P-nutrition strategy of P. x canescens may be different according to this condition. Changes in P concentrations and composition in branch leaves, stem tissues and transport tissues of adult European beech (Fagus sylvatica L.) and their offspring growing at P-poor soils and of adult P. x canescens trees growing on P-rich soils were investigated. Adult beech trees show P storage and P remobilization in the stem in form of inorganic Pi and organic-bound Pi in the bark and wood (Netzer et al., 2017; 2018b). In addition, dormant leaf buds build a ‘start-up capital’ in form of phospholipids (Netzer et al., 2017; 2018b). In contrast, beech offspring did not exhibit any P storage in stem bark and wood but accumulated P in dormant leaf buds. The P-nutrition of P. x canescens markedly differs from that of European beech growing at low soil-P availability (Netzer et al. 2018a). This was mainly due to a lack of tree internal P cycling during annual growth indicated by the absence of establishing P storage pools in twig bark and wood during dormancy. Hence, strategies to economize P nutrition and to prevent P losses had not developed in poplar. The different P nutrition strategies fit well with the growth habitat of both species with F. sylvatica developed on P-poor soil and of the fast growing of P. x canescens at unrestricted P-availability of floodplains. References - Lang F, Bauhus J, Frossard E, George E, Kaiser K, Kaupenjohann M, Krüger J, Matzner E, Polle A, Prietzel J, Rennenberg H, Wellbrock N (2016) Phosphorus in forest ecosystems: New insights from an ecosystem nutrition perspective. Journal of Plant Nutritional Soil Science 179:129–135. - Netzer F, Herschbach C, Oikawa A, Okazaki Y, Dubbert D, Saito K, Rennenberg H (2018b) Identification of phosphorus compounds contributing to economized phosphorus use during annual growth in F. sylvatica trees on P-impoverished soil. Frontiers in Plant Science, resubmitted

- Netzer F, Mueller CW, Scheerer U, Grüner J, Kögel-Knabner I, Herschbach C, Rennenberg H (2018a) Phosphorus nutrition of Populus x canescens reflects adaptation to high P-availability in the soil. Tree Physiology 38:6–24.

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Identification of tolerant pearl millet (Pennisetum glaucum L.) genotypes and association of agronomic and plant traits to low soil phosphorus stress

Riyazaddin Mohammed, Prakash Irappa Gangashetty

International Crops Research Institute for the Semi-Arid Tropics (ICRISAT-Sahelian Center), Sadore, BP 12404, Niger.

Keywords: Pearl millet, Low P tolerance The West and Central African (WCA) Sahel regions are surrounded with the low fertility acid sandy soils and with unpredictable rainfall. Low soil phosphorus (low P) is one of the abiotic stress, limiting crop production worldwide due to its low availability in the soil and inaccessibility of P-fertilizer by the resource poor farmers in WCA. Though pearl millet can withstand high temperatures it cannot tolerate the phosphorus deficiency. The present experiment was carried out to identify the low P tolerant pearl millet genotypes and its association with agronomic and morphological traits in pearl millet. 24 pearl millet genotypes were evaluated in three replications under high P (+P; with P fertilisation (100 kg/ha)) or low P (-P; without P fertilisation) conditions in specified fields, at ICRISAT-Sahelian Center, Sadore, Niger. The analysis of variance for the studied traits showed significant F probabilities for all the traits. The genotype IBMV 8402 performed well in both -P and +P conditions with early maturity, medium plant height, long panicle and high grain yield. The genotypes SOSAT-C88, Souna 3, Mil de Siaka, ICMV IS 85327, and ICMV IS 99001 exhibited high grain yield in both +P and -P conditions when compared with the local check, Sadore local, but the yield factor is decreased to 50% under -P conditions. These genotypes exhibited moderate levels of grain Fe content which is an important trait in tackling the micronutrient malnutrition. Trait associations revealed significant positive correlation of grain yield with days to 50% flowering, plant height and panicle length in both +P and -P conditions, but these traits exhibited significant negative correlation with grain Fe and Zn. Variability was seen in the genotypes used in this study for grain yield and nutrient factors under -P conditions and this can be effectively utilised in developing the high yielding OPV’s or hybrids. Breeding for high grain yield under low P conditions along with the nutrient factors in pearl millet will not only contribute towards the food security within the WCA but also will be helpful in long term by contributing towards the efficient use of a scarce resource by the resource poor farmers.

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Dissection of signaling network in regulating root system architecture to phosphate starvation in Brassica napus

Yalin Li1, Guangda Ding1, Chuang Wang1, Kemo Jin1, Sheliang Wang1, Fangsen Xu1, 2, Lei Shi1Error! Bookmark not defined.2

1 National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan 430070, China

2 Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtze River), Ministry of Agriculture, Huazhong Agricultural University, Wuhan 430070, China

Keywords: Phosphate sensing and signaling pathway, Brassica napus Phosphorus (P) is an essential mineral element required in large quantities by plants. Globally, the availability of P in many soils is poor. Plants have evolved a complex signaling network to adapt to phosphorus deficiency. Oilseed rape (Brassica napus L.) is an important oil crops in China as well as in the world. Brassica napus is a domesticated allotetraploid. In this study, the split-root assay was used to investigate the effect of local P supply on the shoot and root growth of oilseed rape cultivar Zhongshuang 11 (ZS11) at the seedling stage. Shoot dry weight (SDW) of cultivar ZS11 treated with HL (half lateral root was supplied with 625 μM Pi and another half was supplied with 0 μM Pi) showed no significant difference from that treated with HH (both halves of lateral root were supplied with 625 μM Pi), but notably higher than that treated with LL (both halves of lateral root were supplied with 0 μM Pi). Root dry weight (RDW) showed significant differences in various treatments, as follow, HL- (half lateral root that supplied with 0 μM Pi) < LL < HH < HL+ (half lateral root that supplied with 625 μM Pi). P concentration in the shoot of HL treatment showed no significant difference from that of HH treatment, but significantly higher than that of LL treatment. However, P concentration in the root showed remarkable differences in various treatments, as follow, LL < HL- < HH < HL+. P deficiency significantly inhibited the elongation of primary lateral root (PLR), however, increased the second lateral root (SLR) density and length. The length of PLR without phosphorus supply (HL-) was shorter than that of HH treatment, but longer than that of LL treatment. Interestingly, the density and length of SLR decreased significantly in the treatments of HL- as compared with LL, but increased in HL+ as compared with HH. The systemic P-demand signal might stimulate SLR growth and P uptake at high P; systemic P-supply signal might inhibit SLR growth without P in the split-root system. The split-root assay and RNA Seq has been employed to investigate the local and systemic transcriptional response to phosphate starvation in oilseed rape (Brassica napus L.).

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Investigation of the phosphorus storage pools in microalgae by Raman microscopy

Lu Gao1, Peter Mojzes2, Ladislav Nedbal1 1Institute of Bio-and Geosciences, Plant Sciences (IBG-2), Forschungszentrum Julich, Wilhelm-

Johnen-Straße, 52428 Julich, Germany 2Institute of Physics, Faculty of Mathematics and Physics, Charles University, Ke Karlovu 5, CZ-

12116 Prague 2, Czech Republic

Keywords: Microalgae, polyphosphate, Raman microscopy Microalgae are able to acquire and accumulate large reserves of phosphorus, which capacities can be used to sequester this nutrient from wastewater effluents. Clean water and algal biomass are the alga technological products of immense potential for circular bioeconomy in which algae can serve as slow-release fertilizer and soil conditioner. In an earlier study, we demonstrated that dried as well as wet biomass of the microalga Chlorella vulgaris can support the growth of wheat on nutrient deficient soil substrates (Schreiber et al. 2018). Unfortunately, the mechanisms of phosphorous uptake by algae is still not adequately understood. This deficiency is mainly caused by lack of methods, which could rapidly identify and quantify relevant phosphorus chemical forms in situ, in various compartments of an algal cell. Thus, a rapid and non-invasive analysis is crucial for studying dynamic polyphosphate pools in algae, such as during the whole process of algal cell cycles, or particularly in the transitions between the phosphorus starvation and phosphorus uptake, regardless of either overshoot or luxury uptake. Moreover, Raman microscopy could identify and quantify classes of complex macromolecules by their unique vibration fingerprints. Until recently, the use of this highly potent technique to study polyphosphate in algal cells has been rare because of the strong fluorescence emission by chlorophyll molecules that overshadows the Raman scattering signal mainly. An advanced sample-handling method enabled to detect a multitude of energy-transducing and energy-storing macromolecules, including polyphosphate, in situ in a single algal cell (Moudříková et al. 2016, 2017). Here, we present new results on the dynamics of polyphosphate formation and hydrolysis in algal cells by means of Raman microscopy. The initially starved cells of green algae accumulated phosphorus, largely in form of polyphosphate, up to 7% of their dry weight from approximately 1% of typical cells. This accumulation occurred during the culture lag phase, within few hours after adding orthophosphate to the medium, when the cells were neither growing nor dividing. As soon as the growth resumed, the polyphosphate reserves were consumed. This transient accumulation of large amounts of polyphosphate reserves represents an opportunity to produce algal biomass with higher phosphorous content for further agricultural applications. References - Moudrikova Š, Sadowsky A, Metzger S et al (2017) Quantification of polyphosphate in

microalgae by Raman microscopy and by a reference enzymatic assay. Analytical Chemistry, 89: 12006-12013.

- Schreiber C, Schiedung H, Harrison L et al (2018) Evaluating potential of green alga Chlorella vulgaris to accumulate phosphorus and to fertilize nutrient-poor soil substrates for crop plants. Journal of Applied Phycology, 19(Pt B), 529.

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Rice improvement for tolerance to phosphorous deficiency using a QTL analysis and chromosomal segment substitution lines

Kondo Katsuhiko, Matsuda Taro, Ohwaki Shizuka, Pariasca-Tanaka Juan, Wissuwa Matthias Crop, Livestock and Environment Division, Japan International Research Centre for Agricultural

Science, 1-1 Ohwashi, Tsukuba, Ibaraki, 305-8686, Japan

Keywords: P deficiency tolerance, QTL, CSSL Phosphorus (P) is an essential macronutrient for crop growth and is required for agriculture. Farmers rely heavily on P fertilizer application to produce high yields, but the phosphate rock used to produce P fertilizers is a nonrenewable resource. Therefore, it is necessary to improve the P efficiency of crops. The rice variety DJ123 is known to facilitate P uptake from P-deficient soils, with a reported QTL for high root efficiency (RE) on chromosome 11 (Mori et, al., 2016). It further carries a QTL for phosphorous utilization efficiency (PUE) on chromosome 11 (Wissuwa et, al., 2015). To identify novel QTL for P deficiency tolerance, we developed a QTL mapping population using a cross between the indica cultivar IR64 and the aus cultivar DJ123. Based on this bi-parental population, we employed three strategies; 1) QTL analysis under high and low P soil conditions, 2) selection of elite lines as with conventional breeding, 3) development of chromosome segment substitution lines (CSSLs). CSSLs enhance the detection of and allow the confirmation of QTLs identified by genetic studies. We detected some QTLs and elite lines associated with high yields under high and low P soil conditions. These results suggest that the combination of the detected QTLs and CSSLs could lead to improved production of high yielding lines in both phosphorus deficient and high input condition. References - Wissuwa M, Kondo K, Fukuda T,Mori A, Rose MT, Pariasca-Tanaka J, Kretzschmar T, Haefele SM, Rose TJ (2015) Unmasking Novel Loci for Internal Phosphorus Utilization Efficiency in Rice Germplasm through Genome-Wide Association Analysis. PLOS ONE: DOI:10.1371/journal.pone.0124215 - Mori A, Fukuda T, Vejchasarn P, Nestler J, Pariasca-Tanaka J, Wissuwa M (2016) The role of root size versus root efficiency in phosphorus acquisition in rice. Journal of Experimental Botany 67:1179-1189

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Silicon influence on photosynthetic pigments and carbohydrates of wheat cultivars grown under different phosphorus levels

Marlys Andrea Ulloa1,2, Sofía Valeska Pontigo1,2, Paula Andrea Cartes2,3 1Doctorado en Ciencias de Recursos Naturales, Universidad de La Frontera, Francisco Salazar

1145 Temuco, Chile. 2Center of Plant, Soil Interaction and Natural Resources Biotechnology, Scientific and

Technology Bioresources Nucleus (BIOREN), Universidad de La Frontera, Francisco Salazar 1145 Temuco, Chile.

3Departamento de Ciencias Químicas y Recursos Naturales, Universidad de La Frontera, Francisco Salazar 1145 Temuco, Chile.

Keywords: Silicon, carbohydrates, chlorophylls

Low phosphorus (P) availability on soils represents one of the major constraint for

agricultural systems since it limits plant quality and productivity (López-Arredondo

et al. 2014). Phosphorus deficiency strongly affects plant growth, biochemical

metabolic pathways, and photosynthetic efficiency (Hernández and Munné-Bosch

2015). Current evidence has shown that Si supplementation play a beneficial role for

plants specially grown under different environmental stresses (Debona et al. 2017).

Moreover, Si arise as a potential strategy to cope with P shortage. However, so far

few studies have been undertaken to elucidate the impact of Si supply on plants

subjected to P deficiency.

This research aimed to evaluate Si influence on photosynthetic pigments and

carbohydrates accumulation pattern of wheat cultivars grown under different P

levels. A hydroponic experiment was conducted by using two wheat cultivars with

contrasting P tolerance (Púrpura; sensitive and Fritz; tolerant) grown with different

P doses (0, 0.01 or 0.1 mM) in combination with Si treatments (0, 1 or 2 mM).

At the end of experiment, P and Si concentration, chlorophyll a and b, total

chlorophyll, sucrose and starch content were determined. Shoot Si concentration

increased as Si dose rose. However, a reduced Si concentration was observed as the

level of applied P raised from 0 to 0.1 mM P. Even though, Fritz cultivar did not show

significant changes on chlorophyll pigments content, an enhancement in chlorophyll

a and total chlorophyll content was observed in Púrpura at increasing Si supplied. In

addition, sucrose content augmented in shoots (45.4%) and roots (14.6%) of Púrpura

cultivar when 0.01 P was added in combination with 1 mM Si, whereas no differences

in chlorophyll b and starch content were detected among treatments. It has been

reported that Si can enhancement chlorophyll and sucrose contents under plant

stress (Bityutskii et al. 2014; Qin et al. 2016).

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In this study we found that Si supply increased the photosynthetic pigments and

carbohydrates such as sucrose in a P sensitive cultivar Púrpura grown under a P

deficient state.

The understanding the impact of Si on plant metabolism could be exploited as a

potential strategy to improve the productivity of massive consumption crops such as

wheat cultivated on P deficient soils.

References - Bityutskii N, Pavlovic J, Yakkonen K, et al (2014) Contrasting effect of silicon on iron, zinc and

manganese status and accumulation of metal-mobilizing compounds in micronutrient-deficient cucumber. Plant Physiol Biochem 74:205–211.

- Debona D, Rodrigues FA, Datnoff LE (2017) Silicon’s Role in Abiotic and Biotic Plant Stresses. Annu Rev Phytopathol 55:85–107.

- Hernández I, Munné-Bosch S (2015) Linking phosphorus availability with photo-oxidative stress in plants. J Exp Bot 66:2889–2900.

- López-Arredondo DL, Leyva-González MA, González-Morales SI, et al (2014) Phosphate Nutrition: Improving Low-Phosphate Tolerance in Crops. Annu Rev Plant Biol 65:95–123.

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The phosphorus fertilization management affect the quality and yield of Victoria table grapevine

Miro Barbarić1, Adrijana Filipović1, Marko Ivanković1 , Tomislav Ćosić2

1Federal Agro-Mediterranean Institute of Mostar Biskupa Čule no. 10, 88000 Mostar Bosnia and Herzegovina

2Faculty of Agriculture University of Zagreb, Svetošimunska 25, 10000 Zagreb, Croatia Keywords: Table grapevine Victoria, phosphorus, quality

The two-year study were carried out in 2009 and 2010 researching different

phosphorus fertilization rate influence on the quantity and dynamics of phosphorus

of the table vine Victoria variety, as well as the interactions of this ion with macro-

elements in plants on Herzegovina region. Grapevine nutrient oversupply as well as

its shortage can both result in an unbalanced vine growth and poor grape

production, thus mineral fertilization is a powerful tool in viticulture to increase the

yields and improve grapes quality. However, the uptake of one mineral does not

depend only on the nutrient availability in the soil, since interactions among

elements – synergism and/or antagonism – can influence the plant nutrient uptake.

With regard to the content of the macro-element in the vine vegetative plant

material (leaf) of the variety Victoria fertilization did not show a significant influence

on their accumulation, while their oscillations in the values were more reflection of

phenophase sampling, interactions, and weather / seasonal and pedological

conditions that influenced their intensity of receiving and moving through the soil-

plant system. The fertilization experiment was set up according to the method of the

Latin squares with five fertilizer variants. The size of the basic parcel was 24 m²,

which included six pots. Fertilizer variants include control (variant without

fertilization), and fertilizer variants with 100 kg P2O5 ha-1, 200 kg P2O5 ha-1, 300 kg

P2O5 ha-1 and 400 kg P2O5 ha-1. On the based on soil analysis the fertilization

applications were obtained with mineral fertilizer formulation NPK 7:20:30 and

superphosphate 0: 19: 0, while the remaining amount of nitrogen was applied

through two-side dressing with UREE 46%. The collected leaf material of Victoria

varieties during tree phenophases have achieved somewhat higher values of

nitrogen, phosphorus, potassium and magnesium in the second vegetation season

compared to the first year of research, except calcium. Mostly, during both

vegetation seasons the trend of N, P2O5 and K2O falls as vegetation falls down, while

the contents of Mg and Ca in leaf increase with plants aging. In both research years

during the vegetation development phases the fertilization phosphorus doses and

the concentration of macro-elements in the leafs of the grapevine variety of Victoria

have shown eight positive or negative correlation coefficients that reflect strong or

very strong correlations (rxy ≤ -0.75; rxy ≥0.75).

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Managing Phosphorus in the Food System for Environmental Gain Paul J. A. Withers1

1Lancaster Environment Centre, Lancaster University, Lancaster LA1 4YQ, UK

Keywords: Phosphorus, eutrophication, food system

Phosphorus (P) has become a serious and costly pollutant of aquatic ecosystems due

to the inefficient use of manufactured reactive P in the food chain and subsequent

leakage to inland and coastal waters (Withers and Bowes, 2018).

Future agricultural intensification for an expanding, more affluent and urbanising

population and climate change will bring further P pollution pressure on aquatic

ecosystems. This pollution pressure occurs over long timescales and long distances

from the original source, and is therefore very difficult to manage. The P

concentration targets required to reduce eutrophication risk in waterbodies (20-100

g/L) are also very challenging in relation to the amounts of reactive P circulating in

anthropogenic cycles and landscapes. National surpluses of P are driven by reactive

P inputs (fertiliser and feeds), but the causes of P inefficiency and wastage arising

from these inputs are multiple and complex.

Pollution pressures arise due to P inefficiencies at both field scale and regionally, and

subsequent transport to waterbodies in soluble and particulate forms is dependent

on active mobilization and hydrological routing. For agricultural landscapes, a

distinction can be made between the mobilization of previously accumulated

(legacy) P in soils and sediments, and the fresh P (fertilisers and manures) applied

each year. Critical source areas that have high P mobilization risk in active runoff

zones can be managed more sensitively to reduce P loss risk, especially by erosion.

However, alleviating current and future P pollution pressures is also dependent on

reducing P inputs, and the legacy P stores that have accumulated in rural landscapes.

For example, recent modelling predictions suggest that lowering high P soils would

reduce P loading to Chesapeake Bay by 40%, although such drawdown takes time

(e.g Vadas et al., 2018). Similar environmental gains can be predicted for other

catchments. Ultimately, society (producers and consumers) must tackle P pollution

pressure by implementing transformative change to lower P demand in the food

system, use P more efficiently across multiple scales and secure economic routes to

recycle secondary sources of P more sustainably.

A strategic 5R framework for global sustainable P management has been developed

to support this goal (Withers et al., 2015). However, the P load reductions necessary

to reach eutrophication control targets may not be achievable in the short-term in

many areas, and desired ecological gains will likely require the implementation of

additional riparian landscape and food web modifications that are unrelated to P.

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References

- Vadas PA, Fiorellino N.M, Coale FJ, Kratochvil R, Mulkey AS, McGrath JM (2018) Estimating legacy soil phosphorus impacts on phosphorus loss in the Chesapeake Bay watershed. Journal of Environmental Quality 47:480-486.

- Withers PJA, Bowes MJ (2018) Phosphorus the pollutant. In: Phosphorus: Polluter and Resource of the Future: Removal and Recovery from Wastewater, Schaum C, (Ed), IWA Publishing: London UK pp. 3–34.

- Withers PJA, van Dijk KC, Neset TSS, Nesme T, Oenema O, Rubæk GH, Schoumans OF, Smit B, Pellerin S (2015) Stewardship to tackle global phosphorus inefficiency: The case of Europe. Ambio 44:193–206.

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Phosphorus and the ecology of tropical forests Benjamin L. Turner

Smithsonian Tropical Research Institute, Republic of Panama

Tropical forests are among the most species-rich plant communities on earth, which

challenges conventional approaches to understanding how soils shape their ecology.

In particular, phosphorus is widely assumed to be the most important nutrient in the

lowland tropics, but support for this paradigm is equivocal. In this presentation, I will

explore the extent to which phosphorus influences the productivity, diversity, and

distribution of plant species in tropical forests. I will highlight the range of soils that

occur in tropical forests and will argue that pedogenesis and associated phosphorus

depletion is a primary driver of forest diversity over long timescales. I will draw on

data from a regional-scale network of forest dynamics plots in Panama to show that

phosphorus availability is the most important edaphic driver of tree species

distributions, and will suggest potential mechanistic explanations for this pattern in

relation to phosphorus acquisition. Finally, I will present evidence for pervasive

species-specific phosphorus limitation of tree growth on strongly weathered soils in

the lowland tropics, and discuss the implications for the response of tropical forests

to future environmental change.

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Reducing conditions in the vadose zone are associated with colloid and

phosphorus release: evidence from lysimeters and depth profiles

Ruben Warrinnier1, Shy Ysabie1, Camille Resseguier2, Jean-Christophe Gueudet2, Sabine Houot2,

Philippe Cambier2 and Erik Smolders1 1Department of Earth and Environmental Sciences, KU Leuven, Kasteelpark Arenberg 20 box

2459, 3001 Leuven, Belgium 2INRA, UMR 1402 ECOSYS, Ecologie fonctionnelle et écotoxicologie des agroécosystèmes, 78850

Thiverval-Grignon, France

Keywords: Reductive phosphate and colloidal release, colloidal mediated phosphate

leaching

Vertical phosphate (PO4) leaching through the 'unsaturated zone' of agricultural soil

can enrich groundwater with phosphorus (P). This zone is thought to be oxic and

our previous work showed PO4 sorption on particulate and colloidal ferric iron-

and aluminium (oxy)hydroxides (Fe(III)- and Al(oxy)hydroxides) controls P

leaching. In wetlands, i.e. saturated soil, and in the presence of an electron donor

such as organic matter, reductive dissolution of Fe(III) to ferrous iron (Fe(II))

releases bound PO4. The aim of this work was to elucidate field scale PO4 leaching.

Wick lysimeter data (2013 to present), from an agricultural field trial, were

analyzed. Soil cores were sampled in vicinity of the wicks in distinct layers.

Extractions (fresh soil; 1 mM CaCl2; solid/liquid = 0.25 kg L-1; 24 hours shaken; 2500

relative centrifugal force; 0.45 µm filtered) were used to represent the soil solution.

The same was done along a 'redox gradient', i.e. a slope from dry to wet. The P

concentration ([P]) in the wick samples ranged from below limit of quantification (<

LOQ) to 25 µM P. The iron concentrations ([Fe]) ranged from < LOQ to 162 µM and

correlated with [Al] (r = +0.95*; * indicates p < 0.0001 on a log-log relationship). In

turn, [Fe+Al] correlated with [P] (r = +0.69*). The manganese (Mn) concentration (<

LOQ - 10 µM) correlated strikingly with [Fe+Al] and [P] (resp. r = +0.66* and +0.51*).

Depth profiles. [P] in the model soil solutions ranged from 0.16 µM to 41 µM. [Fe]

ranged from 0.86 to 99 µM and correlated with [Al] (r = +0.95*). [Fe+Al] correlated

with [P] (r= +0.75*). However [Mn] (0.01 - 7.41 µM) correlated most strong with [P]

(r = +0.94*) and again with [Fe+Al] (r = +0.88*). [P], [Mn] and [Fe+Al] were low plough

zone, largest in the plough pan (28 - 35 cm depth) and decreased with increasing

depth, i.e. decreasing organic matter (OM) content (all *). Redox gradient. Identical

correlations were found. Pooling the data shows large [P], [Mn] and [Fe + Al]

associate with reducing conditions (large OM, high water content and low pH).

Reducing conditions in the vadose zone reduce and dissolve Mn(IV) to Mn(III or II)

and later Fe(III) to Fe(II). When this cement-like structure of the matrix dissolves,

colloids and sorbed PO4 are released. Next, the causality behind the presented

correlations and the effect on P migration will be investigated.

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Colloidal phosphorus: linking stream waters to soils

Gérard Gruau1, Sen Gu1, Laurent Jeanneau1, Marie Denis1, Patrice Petitjean1, Rémi Dupas2,

Chantal Gascuel-Odoux2, Ophélie Fovet2 and Martine Le Coz-Bouhnik1

1Univ Rennes, CNRS, Géosciences Rennes, UMR 6118, F-35000 Rennes, France 2INRA, UMR 1069, SAS, AGROCAMPUS OUEST, F-35000 Rennes, France

Keywords: Colloids, catchment, soil-water interface

Colloids (1 to 1000 nm) have been widely suggested as important carriers of

phosphorus (P) in agricultural soils. This suggestion is, however, so far based on

colloids extracted from laboratory soil solutions, with no direct field evidence. Here,

we conducted the first field monitoring study of Pcoll release and transport dynamics

in a small agricultural catchment located in Western France, during one hydrological

year. Results evidenced that Pcoll is an important fraction of the total dissolved P (TP)

fraction (<0.45 m) in both soil and stream waters (mean=39%). However, a decrease

in the proportion of Pcoll was found along the soil-stream continuum, suggesting

either retention of part of the released Pcoll during transport or a dilution by deep

groundwater with low Pcoll concentrations. The proportion and composition of Pcoll

were studied in detail along two soil transects (A and B), and in the stream

immediately adjacent to them. A spatial consistency was found in the proportion of

Pcoll which were comparatively higher in soil and steam waters from transect B

(mean=52% and 32%, respectively), as compared to transect A (mean=42% and 19%,

respectively). A detailed survey of the Pcoll composition revealed a major difference

between soil waters from transects A and B, the colloids being equally composed of

colloidal-MRP (molybdate-reactive P) and colloidal-MUP (molybdate-unreactive P)

in transect A, as against mainly in the form of colloidal-MUP (mean=70%) in transect

B soil waters. However, this difference was not maintained in corresponding stream

waters. This may suggest that colloidal-MRP in colloids occur in the formed of outer

sphere complexes which were destabilized in the stream due to higher pH

conditions. Considering all soil and stream water samples, a negative correlation was

found between the proportion of Pcoll in TP and the P:Fe ratios. Concentrations of

Pcoll were also found to correlate with DOC concentrations, suggesting a potential

influence of the soil properties and local groundwater chemistry on Pcoll

concentrations. Overall, this study confirms that Pcoll is an important fraction of the

TP released in agricultural soils and that this fraction can be efficiently transported

to streams by shallow groundwater flow. It also indicates that the composition of the

released Pcoll may vary in space and time and that retention processes probably occur

at the soil-stream interface with the potential of modifying the composition of the

Pcoll.

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Transfer of Phosphorus from Land to Waters: A Long-Term Climate

Perspective

Philip M. Haygarth1, The UK NUTCAT & DTC team1 1Lancaster Environment Centre, Lancaster University, Lancaster, LA1 4YQ, United Kingdom.

Keywords: Phosphorus, transfers, climate change

This oral presentation will give both a reflective and forward-looking personal

viewpoint on the transfer of phosphorus from land to waters (Haygarth et al., 2005),

with a particular focus on climate and land use change in the medium and long term.

A tweet from the author during the record breaking Storm Desmond, which resulted in

unusually high loads of phosphorus transferred into the UK Rivers Eden and Lune, and

ultimately into the Irish

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The devastating hurricanes and storms that have occurred recently around the world

remind us of the great dynamics and power in our weather and climate. As well as

the immediate flood and human hazards, such events can have implications for the

earth’s phosphorus cycle too. In the UK, my team has been studying the extent to

which phosphorus losses from land to water will be impacted by climate change and

land management, with detrimental impacts on aquatic ecosystems and food

production. There is a great challenge in determining this, with all the complexities,

controversies and uncertainties that surround it. I will describe work that uses a

combination of methods to evaluate the impact of projected climate change on

future phosphorus transfers, and to assess what scale of agricultural change might

be needed to mitigate these transfers. We combined high-frequency phosphorus

flux data from three representative catchments across the UK, a new high-spatial

resolution climate model, uncertainty estimates from an ensemble of future climate

simulations, two phosphorus transfer models of contrasting complexity and a

simplified representation of the potential intensification of agriculture based on

expert elicitation from land managers. We show that the effect of climate change on

average winter phosphorus loads (predicted increase up to 30% by 2050s) will be

limited only by large-scale agricultural changes (e.g., 20–80% reduction in

phosphorus inputs). Some of this work was published in Nature Communications

August 2017 (Ockenden et al. 2017) and is available here doi:10.1038/s41467-017-

00232-0. The work involves many years of work and the contribution from multiple

authors, who will be acknowledged during the presentation.

References

- Haygarth PM, Condron LM, Heathwaite AL, Turner BL, Harris GP (2005) The

phosphorus transfer continuum: Linking source to impact with an interdisciplinary and multi-

scaled approach. Science of the Total Environment 344: 5-14.

- Ockenden MC, Hollaway MJ, Beven KJ, Collins A, Evans R, Falloon P, Forber KJ, Hiscock

K, Kahana R, Macleod C (2017) Major agricultural changes required to mitigate phosphorus

losses under climate change. Nature Communications 8. doi: <li data-

test="doi">doi:10.1038/s41467-017-00232-0.

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Can water quality models better reflect our understanding of soil

phosphorus pools?

Heidi Peterson1, Tom Bruulsema2, Rebecca Muenich3 1International Plant Nutrition Institute (IPNI), 15240 30th Street North, Stillwater, Minnesota,

USA 2IPNI, Guelph, Ontario, Canada 3Arizona State University, Tempe, Arizona, USA

Keywords: Soil Test P, water quality models, P cycling

Understanding how to properly

manage phosphorus (P) sources and

loss pathways from agricultural land

continues to be a global

environmental challenge. Nutrient

reduction strategies and the

implementation of management

practices to meet water quality

goals are often developed with

information from water quality

models.

Figure 1: Phosphorus cycling in crop production systems.

The quantification of environmental P losses and the effectiveness of conservation

practices adopted to reduce these losses are often modeled based on edge-of-field,

in-stream, or sub-surface drainage water samples, with the use of default labile P soil

values. Although nutrient management decisions at the field scale are ideally made

based on site-specific soil test P concentrations, this data is not directly integrated

into water quality models. In order to improve the ability for water quality models

to more accurately incorporate 4R nutrient management practices (applying P at the

Right time, in the Right place, at the Right rate using the Right source) into

watershed-based implementation scenarios, models must become aligned with

current soil fertility and P biogeochemistry science. This presentation will review

how water quality models currently estimate P pools and interactions in the soil

matrix and suggest improvements that could be adopted to integrate soil test P and

current knowledge of P cycling.

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Catchment-based soil sampling and risk mapping to encourage

sustainable phosphorus management and water protection. Rachel Cassidy1, Alex Higgins1, Phil Jordan2, John Bailey1, Ian Thomas1

1Agri-Food and Biosciences institute (AFBI), 18a Newforge Lane, Belfast BT9 5PX, Northern

Ireland. 2School of Geography and Environmental Sciences, Ulster University, Coleraine BT52 1SA,

Northern Ireland.

Keywords: Soil sampling, critical source area, phosphorus, sustainable nutrient

management.

Soil nutrient testing is a key

component of strategies to

increase farm profitability and

reduce agricultural impacts on

water quality, yet it is not

routine on most Northern

Irish farms. As part of the EU

Exceptional Adjustment Aid

package (2017-18) a

programme was developed to

provide free soil sampling and

nutrient management advice to farmers across the region. An element of the scheme

focused on a 200 km2 river catchment, dominated by grassland agriculture at a range

of intensities (Fig. 1). Within this area field scale soil sampling was undertaken on

513 farms (7,772 fields) across 11 sub-catchments where chemical and biological

water quality monitoring have been ongoing for several decades. In addition, high-

resolution LiDAR topographic data were used to derive critical source area risk maps

(Thomas et al, 2016), denoting sub-field areas at highest risk of phosphorus (P)

mobilisation from fertilisers and soils during rainfall events. These high-risk areas

should be prioritised for on-farm mitigation to reduce nutrient loss to surface waters.

Maps of soil nutrient status, fertiliser recommendations and hydrological risk,

together with advice and training, were provided to all participants. In this early

review period we assess the scheme to date and present initial findings. In particular

we examine the distributions of soil nutrient status across farm types, scales of

operation and landscape types and evaluate the soil measurements and risk models

against water quality monitoring data through the catchment. Key challenges, for

both science and policy, arising from this work will be discussed.

References: Thomas IA, Mellander P-E, Murphy PNC, Fenton O, Shine O, Djodjic F, Dunlop P, Jordan P (2016) A sub-field scale critical source area index for legacy phosphorus management using high resolution data. Agriculture, Ecosystems & Environment 233: 238-252.

Figure 1: Upper Bann catchment area, Northern

Ireland.

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Potential of riparian buffer strip species to recycle phosphorus in the

agricultural landscape

Lawrie K. Brown, J. A. Stockan, M. Stutter, C. Hawes, T. S. George

The James Hutton Institute, Invergowrie, Dundee, DD2 5DA

Keywords: P recycling, buffer strips, field scale

The sustainability of agriculture needs to be improved. It is important to maintain crop yield, while reducing the environmental impact of agriculture. Methods are required to reduce the inputs of inorganic fertilisers and ‘close the loop’ on nutrients like phosphorus (P) that can otherwise become environmental pollutants. One way to achieve this is to promote recycling of P within the agricultural landscape. We investigated the extent to which green manure, produced in riparian buffer strips, can provide P to crop plants. Species typical of Scottish riparian buffer strips were tested for their ability to accumulate P in shoot tissue and their potential for enhancing the utility of the resulting green manure in promoting crop growth both in glasshouse and field experiments. The species tested varied in the amount of P they accumulated in their tissue (38-fold difference) and different species had a range of impacts on the availability of C, N and P in soils. We found that green manure derived from riparian buffer strips only replaced a small proportion of the requirement for fertiliser both in controlled conditions and in the field when compared to conventional fertiliser additions. This was also the case when the species composition of the buffer strips in the field had been manipulated to contain species known to accumulate large amounts of P. However, there were other advantages observed from manipulating the buffer strip species composition, including greater diversity of plants and insects, reduced spikes of nitrate concentration in soil water and reduced NOx emissions. Characteristics of the individual species, plant community composition and timing of cutting will need to be understood to make the buffer strip vegetation a more effective source for recycling P. We demonstrate that this cannot be done solely by selecting specific species based on their nutrient accumulation characteristics.

Figure 1. P accumulation of a range of common buffer strip species grown for 12 weeks in a sand compost mix amended with N and P to levels typical of a riparian buffer strip.

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Progress in development of a more P-efficient grassland system for southern

Australia

Richard J Simpson1, R. C Hayes2, G. A Sandral2, R. A Haling1, A. Stefanski1, Suzanne P Boschma3,

Matthew T Newell4, Megan H Ryan5, Daniel R Kidd5, Bradley J Nutt6 1CSIRO Agriculture & Food, GPO Box 1700, Canberra, 2601, Australia. 2NSW Department of

Primary Industries, Australia. 3NSW Department of Primary Industries, Australia. 4NSW

Department of Primary Industries, Australia. 5School of Plant Biology & Institute of Agriculture,

The University of Western Australia, 6Murdoch University, Australia

Key words: P-efficient, serradella, pasture

The soils in southern Australia used for grass-legume pastures are often phosphorus

(P) deficient. Farmers must apply P fertiliser to achieve high production. P-balance

efficiency (PBE=100*Poutput/Pinput) is low because the soils accumulate much of the

applied P. Research to improve P efficiency has systematically sought to: (i) identify

opportunities for high grassland production with less P fertiliser; (ii) capture one such

opportunity using P-efficient pasture legumes; (iii) test and develop the agronomic

fitness of these plants for diverse farm environments. The opportunity: P-deficient

soils are fertilised to achieve a “critical” soil test P (STP) benchmark that ensures high

production. However, on sheep/beef farms (median PBE ~20%), annual maintenance

fertiliser applications of 10 kg P/ha result in P accumulating in grazed fields at ~8 kg

P/ha/year. A long-term field experiment (LTFE) has confirmed that P accumulation

is positively related to the STP concentration at which a soil is maintained. In

temperate grasslands, legumes determine the critical STP because they have higher

P requirements than their companion grasses. Productive legumes with lower critical

P requirements should result in less P accumulation and reduced fertiliser-P

inputs.The search: Trifolium subterraneum (subterranean clover) is the most widely

grown pasture legume but has a relatively high critical STP requirement (e.g. 15 mg

Olsen P/kg soil, field soils 0-10 cm depth). We examined the growth in response to

P-fertiliser application of a number of alternative legumes at 4 field sites and in

controlled-environment studies. Standout species in the field and laboratory

experiments were Ornithopus sativus (French serradella) and O. compressus (yellow

serradella) with putative critical field STP of ~10 mg Olsen P/kg. Results from the LTFE

suggest that use of these species may reduce P-fertiliser inputs by ~30%. Legumes

fit for purpose: O. compressus and O. sativus are already key legumes in some crop-

ley farming systems and in grasslands on deep, acid sandy soils. Expansion of these

species to a wider area of permanent-pasture farming requires cultivars that tolerate

heavier soils, yield well and persist at a reasonable botanical density over many

years. Current research is examining herbage production, stress tolerances,

phenology, seed production and dormancy in a search for serradella ecotypes that

can broaden the adaptation zone for these more P-efficient pasture species.

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Effect of fertilizer levels and sward diversity on ryegrass and clover

uptake of phosphorus and micronutrients

Tegan Darch1, Ellen Fletcher2, Martin Blackwell1 1Rothamsted Research, North Wyke, Okehampton, EX20 2SB, UK.

2Imperial College London, South Kensington Campus, London, SW7 2AZ, UK.

Keywords: Grassland, Intercropping, micronutrients, phosphorus use efficiency

By intercropping plants with different root traits, such as root hairs and exudates,

complementary use of phosphorus (P) resources often results in a greater overall

yield and P uptake than when plants are grown in pure swards. The stress-gradient

hypothesis suggests that complementary use of P resources in mixed swards

should increase as soil P decreases, while nitrogen (N) fertilizer is likely to depress

legume growth relative to grass growth. The objectives of this project were i) to

determine how the P and N status of soil affects the complementary use of P and

micronutrient resources in grasslands, and ii) to compare the productivity of mixed

ryegrass-clover swards with pure stands under different P levels. A pot trial was

conducted using a soil with low available P (Olsen P 6.7 mg kg-1, index 0).

Experiment treatments were fully factorial, with low and high P fertilizer (40 and

600 kg ha-1 P2O5, as NaH2PO4.2H2O), low and high N fertilizer (0 and 60 kg N ha-1, as

NH4NO3), pure stands of AberHerald white clover and AberMagic ryegrass, and

mixed swards with a 1:3 ratio of clover to ryegrass. All pots received K2SO4 (60 kg ha-

1). Plants were harvested to 2cm, and herbage from the second cut was analysed for

total P and micronutrient concentrations using nitric and perchloric acid digestion,

with analysis by ICP-OES or ICP-MS. Mixed swards produced more biomass than pure

stands, but there was no significant effect (p<0.05) of fertilizer treatment on the Land

Equivalent Ratios (LERs) of yield (Fig 1).

Plant P concentrations were increased (p<0.001) by both P and N fertilizer additions,

and grass contained higher P concentrations at high soil P, while clover contained

higher P concentrations at low soil P. Phosphorus fertilizer addition resulted in

increased plant Fe concentrations, but decreased Ca, Cu, K, Mg, Mn and S

concentrations, and this was further exacerbated by N addition. Typically,

micronutrient concentrations in clover were greatest in pure stands, and greatest in

grass in the mixed swards. These results indicate that mixed swards can be beneficial

for improving biomass production, but highlight that ryegrass P and micronutrient

concentrations are improved at the detriment of these nutrients in clover. Nitrogen

fertilization results in improved P uptake, but it should be noted that when using N

and P fertilizer, there may be a trade-off between productivity and nutritional value.

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Layered double hydroxides as slow-release phosphorus fertilizer

Maarten Everaert1,2, Fien Degryse, Kris Dox, Rodrigo C da Silva, Mike J. McLaughlin, Dirk De

Vos, Erik Smolders 1 KU Leuven, Department of Earth and Environmental Sciences, Kasteelpark Arenberg 20 box

2459, 3001 Leuven, Belgium. 2 VITO NV, Sustainable Materials, Boeretang 200, 2400 Mol, Belgium.

Keywords

Slow-release fertilizer, Layered double hydroxide (LDH), Anion exchange

Phosphorus (P) is an important limiting nutrient in crop production. Common P

fertilizers are soluble P forms produced from rock phosphate, a practice facing

several issues: (i) poor agronomic effectiveness in P fixing soils, (ii) limited rock

phosphate reserves, and (iii) P runoff/leaching causing eutrophication. Hence,

research focused on P recycling and development of more efficient fertilizers with

lower environmental risks. Here, layered double hydroxides (LDHs) are assessed as

an alternative and sustainable P fertilizer. The LDHs are inorganic anion-exchange

materials consisting of positively charged layers and a negatively charged

interlayer of anions (e.g. phosphate, PO4). The LDHs can be used as adsorbent for

PO4 in waste streams. We hypothesize that applying PO4-LDHs to soils results in a

slow PO4 release via exchange with carbonate (CO3). This slow release could

bypass P fixation and increase the agronomic effectiveness compared to soluble P

fertilizers. Via coprecipitation, different Mg-Al LDHs were synthesized by varying the

Mg/Al ratio and the pH, and subsequently exchanged with PO4. The mechanisms of

anion exchange on the solid phase were identified by exchange stoichiometry

measurements and isotope exchange techniques (33PO4, 14CO3). The PO4 release

was characterized to prove the slow-release characteristics of LDHs for PO4. In a

greenhouse trial with an acid and a calcareous soil, the agronomic effectiveness of

powder and granular LDH fertilizers was compared to that of soluble mono-

ammonium phosphate (MAP) and struvite. A simulated rainfall study examined

differences in P runoff losses between these fertilizers. Results showed that an

increasing LDH layer charge (decreasing Mg/Al) increased the PO4 uptake. The

reaction stoichiometry of exchanging anions strongly depended on the Mg/Al ratio

and synthesis pH, and revealed the PO4 speciation in different LDHs. Desorption of

PO4 from LDHs in exchange with CO3 anions was indeed slow, but also incomplete.

Interlayer anion diffusion in LDHs was found to partly explain this incomplete PO4

desorption. Plants took up considerably more P from granular MAP compared to LDH

and struvite; differences among powder forms were small. Finally, P runoff losses

from MAP application largely exceed those from LDH and struvite application. Taken

together, the LDH fertilizer offers a viable option for P recycling in agriculture. Yet,

compared to soluble P fertilizers, no increased P uptake by plants was obtained.

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Variation in tree and microbial traits and functioning along natural

phosphorous gradients in Amazonian rainforests Ivan A. Janssens

Research Group Plants and Ecosystems

Centre of Excellence Global Change Ecology

Antwerp University

Within the frame of the ERC-Synergy project ‘IMBALANCE-P’, the impact of

elemental imbalances on the functioning of ecosystems is being studied. Many

regions in the Amazon basin are characterized by very low phosphorous (P) contents

and availabilities, and their productivity is therefore often assumed to be

phosphorous-limited. To study how rainforest plants and microbes adapt to low

phosphorous conditions and how this translates into altered functioning, the

IMBALANCE-P team has established two long-term PxN fertilization experiments,

studies a network of research sites spanning a large gradient of precipitation and soil

texture, and studies topographic variation in plant and microbial functioning along

transects in Peru (high-P soils), Brazil (low-P sedimentary soils), and French Guiana

(low-P residual soils). Here, the first results from the regional gradient study and the

topography gradient study will be shown, with a focus on variation in P and carbon

cycling.

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Decreasing foliar P concentrations in European forests Josep Peñuelas1,2, Tanja Sanders3, Marcos Fernández-Martínez1,2, A Schmitz3, Jordi Sardans1,2

1 CSIC, Global Ecology Unit CREAF-CSIC-UB-UAB, 08193 Bellaterra, Catalonia, Spain 2 CREAF, 08193 Cerdanyola del Vallès, Catalonia, Spain

3 Thünen Institute of Forest Ecosystems, 16225 Eberswalde, Germany

Keywords: decreasing foliar concentrations, Europe, P The continuous global rise of atmospheric CO2 concentrations, the increase in regional droughts, the warming, and the N and S loads by atmospheric deposition in Europe have affected forest nutritional condition in the last decades (Jonard et al., 2015; Sanders et al., 2017). We revisited the available data until current year of the International Co-operative Program on Assessment and Monitoring of Air Pollution Effects on Forests (ICP Forests) both Level I and II. This is program for European forest motorization driven by the Working Group on Effects (WGE) under the UNECE Convention on Long-range transboundary Air Pollution (CLRTAP). Since the beginning of these data collection in 1992, some studies have observed a general trend of decreases, with some exceptions, in foliar nutrient concentrations for the main tree forest species across Europe, e.g. from 1992 to 2009 (Jonard et al., 2015). More recently, analyzing the data of foliar N and P concentrations and N:P concentration ratio of Fagus sylvatica, Picea abies and Pinus sylvestris from data collected during 1992–2015 on the intensive forest monitoring plots of the ICP Forests programme, Sanders et al. (2017) also reported a general trend to N and P foliar concentrations decreases (except N concentrations in Pinus sylvestris) and increases of foliar N:P ratio since 2000. We now used the data from ICP Forest,s not only from level II plots but also from level I plots with available data, and analyzed the trends of foliar N, P, S, Ca, Mg and K concentrations and their pairwise ratios across different latitudes, countries, and species. We also analyzed the role of climatic changes and N and S deposition underlying the foliar nutrient concentrations across Europe along the period from 1992 to 2016. We found an overall decrease of the concentrations of all nutrients in southern and central Europe and an increase in northern Europe. The results strongly suggest that drought is underlying the decreasing foliar concentrations of P and other nutrients in southern Europe (Mediterranean forests). Sulfur foliar concentrations have also strongly decreased in central Europe forest associated with the great drop of S deposition during this period. In northern latitudes, on the contrary, there is a general increase of foliar nutrient concentrations of boreal forests, probably related with warming.

References

- Jonard, M. et al. (2015) Tree mineral nutrition is deteriorating in Europe. Global Change

Biology 21, 418-430.

- Sanders, T. et al. (2017). Trends in foliar nitrogen and phosphorus concentrations and

ratios since 2000. In Michel, A., Seidling, W. (eds.) Forest Condition in Europe. Technical

Report of ICP Forest. Report under the UNECE Convention on Long-Range Transboundary

Air Pollution (CLRTAP). pp 39-47.

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Phosphorus bio-availability along an elevation transect in a tropical

montane forest - Rwenzori, Uganda.

J. Okello1,2,3, Marijn Bauters1,2, H. Verbeeck2, J. Kasenene3 and P. Boeckx1

1Isotopes Bioscience Laboratory – ISOFYS, Ghent University, Coupure Links 653, 9000 Gent,

Belgium. 2CAVLAB - Computational and Applied Vegetation Ecology, Ghent University, Coupure

Links 653, 9000 Gent, Belgium. 3Mountains of the Moon University, Fort Portal, Uganda.

Keywords: Elevational transect, phosphorus, tropical forest

Context: Tropical montane forests are important terrestrial ecosystems with high

carbon storage, species endemism and biodiversity. Due to variation in climate and

forest types, elevational transects in montane forests are an open-air natural

laboratory for studying the influence of abiotic factors on forest composition,

functionality and biogeochemical cycles. As such, through difference in climate and

soil profile development, it is generally assumed that nutrient limitation shifts from

P to N limitation with increasing elevation. To better understand environmental

controls on P bio-availability in tropical forests, we setup an elevational transect on

Mt. Rwenzori in Uganda, ranging from 1264 to 2886 m asl. We collected sunlit

mature canopy leaf and soil samples (0-10 cm, 10-20 cm and 20-30 cm soil depth).

Analysis of available P in top 30 cm using the resin method revealed a positive

correlation between available P and elevation, which ranged from 0.46% of total P

at 1264 m asl to 2.63% at 2886 m asl. Surprisingly, canopy leaf P content showed

negative correlation with elevation, ranging from 0.15% at 1264m asl to 0.09% at

2886 m asl. Meanwhile, canopy N:P ratio indicated P limitation at lower elevations

as well as higher elevations with mid elevations showing either N or P limitation or

co-limitation of N and P when compared against N:P ratio thresholds suggested by

Koerselman and Meuleman (1996). Therefore, P nutrition seems to be influenced by

additional factors than soil P availability alone.

References

- Koerselman W, Meuleman AFM (1996). The vegetation N:P ratio: a new tool to detect

the nature of nutrient limitation. J Appl Ecol 33: 1441-1450.

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Soil phosphorus and soil nitrogen are related to sugar and amino acid

composition of nectar and pollen of Succisa pratensis and Calluna vulgaris

Tobias Ceulemans1, Reine Spiessens1, Olivier Honnay1 1 Plant Conservation and Population Biology, Department Biology, University of Leuven,

Kasteelpark Arenberg 31, B-3001 Leuven, Belgium.

Keywords: Pollinator crisis, nutrient pollution, food quality, nectar, pollen, soil

nitrogen, soil phosphorus

Worldwide decline of pollinators is frequently attributed to five main drivers:

increase in invasive alien species, increase in pathogens, climate change, increased

used of biocides and loss of floral food resources. This loss of floral resources is

attributed to the steep decline of plant

species in intensively used agricultural

landscapes, frequently attributed to

nutrient pollution. However, next to the

loss of food quantity, there may also be a

loss of food quality associated with the

increased in soil phosphorus and soil

nitrogen availability.

Here, we investigate the hypothesis that

nutrient pollution in agricultural landscapes

may change sugar and amino acid

composition of nectar and pollen. We

collected nectar and pollen samples of

Succisa pratensis Moench and Calluna vulgaris L. along a gradient of nutrient

pollution in Europe. We found that an increase in soil phosphorus and soil nitrogen

was linked to plant species specific changes in glucose and fructose concentration in

the nectar. Additionally, amino acid composition differed strongly among both plant

species, and was also linked to soil phosphorus and soil nitrogen. Our results show

that nutrient pollution has the potential to change nectar and pollen composition,

which may subsequently change food quality of pollinators.

We recommend further research to determine the precise effects of these changes

in nectar and pollen composition on the fitness of pollinators.

References

- Ceulemans T, Hulsmans E, Vanden Ende W, Honnay O (2017) Nutrient enrichment is

associated with altered nectar and pollen chemical composition in Succisa pratensis Moench and

increased larval mortality of its pollinator Bombus terrestris L. PLoS ONE 12(4): e0175160

.

Figure 1: Pollinators of the genus Bombus on a flower of Succisa pratensis

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POSTER SESSION Wednesday 12 September

Theme 4

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Response of soybean to the fertilization by natural phosphate rock of

Togo in the Central and northern regions of Togo Elidaa Daku1, Agnassim Banito2, Mianikpo Sogbedji2

1GRP Climate Change and Agriculture, Institut Polytechnique Rurale de Formation et de

Recherche Appliquée (IPR IFRA), BP 06, Katibougou, Mali. 2Ecole Supérieure d’Agronomie, Université de Lomé, BP 1515, Lomé, Togo.

Keywords: Phosphate, Soybean, Togo

This study conducted in 2011, aims to improve soybean yield through the

valorization of local phosphate rock. The effectiveness of natural phosphate rock

from Togo (PNT) and its combination with triple super phosphate (TSP) was assessed

in comparison with the triple super phosphate (TSP) as a reference, with a

randomized block, in two sites namely Alibi 1 in the Central region and Sarakawa in

Northern region of Togo. This effectiveness was assessed, firstly, by measuring

soybean growth parameters and yield and secondly by the economic analysis of the

adoption of these fertilizers. The results shows that the use of phosphate fertilizer,

considering all our options had no positive effects on growth and yield parameters

of soybean at Sarakawa. At Alibi 1 site, the contribution of the PNT as phosphate

fertilizer alone had no positive effects on all the assessed crop parameters. But, the

effects of the combination TSP + PNT were statistically similar to those from the

soluble fertilizer TSP. Indeed, TSP + PNT had improved significantly (p ≤ 0.05) as the

TSP, the soybean plant height, grain yield (475.1% compared to PNT) and also

canopy, the mass of 1000 grains. Moreover, these different phosphate fertilizers

have no significant effect on the number and weight of pods produced. The

economic analysis reveals that the use of the combination TSP + PNT is more reliable

for phosphorus fertilization of soybeans in areas under phosphorus deficiency. In

conclusion, the soybean fertilization by the natural phosphate rock from Togo, the

first year of its application, can improved the productivity of this crop, mostly in area

under phosphorous deficiency , if it’s combined to soluble phosphate fertilizer

soluble which will react as starter for phosphorus accessibility to the crop.

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How to increase plant access to the legacy P in tropical soils Luis Prochnow1, Alvaro Resende2, Eduardo Caires3, Paulo Pavinato4, Heidi Peterson5, Tom

Bruulsema6 1IPNI Brazil, Av. Independencia 350, Piracicaba, Brazil, 2Embrapa Maize and Sorghum, Sete

Lagoas, Minas Gerais, Brazil, 3UEPG, Av. Carlos Cavalcanti 4748, Ponta Grossa, Brazil, 4ESALQ/USP, Av. Pádua Dias 11, Piracicaba, Brazil, 5IPNI, Stillwater, Minnesota, USA, 6IPNI,

Guelph, Ontario, Canada

Keywords: Legacy P, P use efficiency, P recovery Phosphorus (P) is one of the most studied nutrients for plant nutrition worldwide and there are many concerns regarding the availability of this finite element’s rock resource and reserves for future generations. In tropical regions, with soils predominantly with an oxidic or 1:1 mineralogy, it gains even more attention owing to high fixation, which tends to turn P into forms less available to plants. Currently, this nutrient is applied in higher amounts than removed by plants, which leads to a stock of P in less available forms in the soil (Legacy P). Recently, some researchers have been calculating the legacy P and discussing possibilities to recover such forms of the nutrient to decrease the input dependency in a near future. There are industrial and agronomic practices that may increase efficiency of P use from mining to field operations and recovering legacy P seems to be a profitable option. In this paper the intention is to focus on agronomic practices in tropical regions that can recycle some legacy P into forms more available to plants. The main agronomic practices suggested include: (1) management of soil acidity with lime and phosphogypsum applications, (2) crop rotation, and (3) development or selection of plant species or cultivars with higher efficiency in recovering P from the soil. It is well known that soils in the tropics are generally acidic and that adjusting the soil pH to match crop needs can in parallel increase P availability. Phosphogypsum has been proven to ameliorate soil conditions in deeper soil layers by decreasing aluminum and/or increasing calcium levels, which may lead to development of deeper plant roots capable of accessing more water and nutrients under stressed conditions. Recently, several studies have shown the advantages of integrating grain crops with grasses for increasing soil health and availability of P through the soil profile (Figure 1). It is also recognized that different plant species or cultivars may vary in their capacity to absorb nutrients from the soil. All these practices should be seriously considered in strategic plans to recover a portion of the legacy P from tropical soils, which will optimize P resources, benefiting farmers and food security in a medium to long time frame.

Figure 1. Intercropping of maize and grass (Urochloa ruziziensis) in Mato Grosso, Brazil. This kind of ecological intensification represents a successful option to optimize nutrient cycling for crop systems in tropical soils.

Theme 4

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Phos4You project: Phosphorus availability of phosphorus fertilizers recovered from municipal wastewater

Aleksandra Bogdan1, Ciaran O’Donnell2, Marina Le Guédard3, Evi Michels1, Ivona Sigurnjak1, Erik Meers1

1Faculty of Bioscience Engineering, Ghent University, Coupure links 653, 9000 Ghent, Belgium. 2 Department of Civil, Structural and Environmental Engineering, Cork Institute of Technology, Bishopstown, T12 P928 Cork, Ireland.3 Laboratoire de Biogenèse Membranaire INRA Bordeaux

Aquitaine – Bat A3 71 avenue Edouard Bourlaux- CS20032 33140 Villenave, France.

Keywords: Recovery, P fertilizers, P availability

The current European Fertilizer Regulation1, next to the national legislation2, implies the use of several different chemical methods to assess phosphorus (P) availability in fertilizers. The variety of those methods is large and comparison between them is difficult. With the emerging production of recovered P fertilizers, adequate measurements of P availability are needed. The Interreg project Phos4You recognizes this demand for standardized quality assessment methodology, in particular P availability. Ten different chemical P extraction and two P determination methods are being evaluated on struvites, P-slag, Fe-P pellets and ash recovered from municipal waste water and compared to triple superphosphate. Also, plant experiments are being carried out in pot and field trials. Multi-nutrient fertilizer (NIST SRM) is used as a reference. Pot trials are conducted with 3.5 g/m3 seeds of ryegrass and P-poor substrate soil, with incremental addition of fertilizer (30, 60 and 90 kg P2O5/ha). Essential nutrients other than P are being supplied with continuous addition of Hoagland solution to avoid deficiencies for other nutrients. Pot trials are run in parallel in 3 countries (BE, IR, FR). The first pot trial mimics plant uptake measurements with passive sampling techniques (i.e. Diffusive Gradient in Thin films (DGT) (iron-oxide binding layer), Rhizon and Plant Root Simulator (PRS) probes) on a weekly basis. Plant height and dry matter is being determined along with chemical P plant extraction measurements. In the second trial, P lipid index is examined as an early P availability indicator whereas the third trial focuses on field testing of struvite on different soil types (i.e. commonly found in Ireland and P-poor substrate soil). Moreover, field trials with struvite are run for scale validation where the product is being tested on two different soil types in Ireland. Chemical extraction methods, passive sampling techniques and biomarker experiments are being compared to find the most efficient way of measuring the P availability. It is hypothesized that biomarker and passive sampling methods can give fast results (compared to the pot experiment) with better correlation to real plant uptake than chemical extraction. The resulting standardized methodology will define the most effective P availability method for the various products from different processes and locations, while ensuring the applicability of the recycled material on the market.

References

- European Commission (2003) Regulation (EC) No 2003/2003 of the European parliament and the council. Official journal of the European Union L 304:1-194.

- Amery, F and Schoumans, O, F (2014) Agricultural phosphorus legislation in Europe. Merelbeke, ILVO 45.

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Anaerobic digestates and animal slurries as alternative phosphorous source for plant nutrition: an example of circular economy

Marco Grigatti1, Silvia Mancarella1, Claudio Ciavatta1, Claudio Marzadori1

1DiSTAL – Department of Agricultural and Food Technologies – Alma Mater Studiorum University of Bologna – Viale Fanin, 40 40127 – Bologna Italy

Keywords: Phosphorus fractionation, apparent recovery fraction, recycled organic matter

Phosphatic fertilizers are mainly derived from phosphate rocks (PR) a non-renewable source, thus representing an incoming issue in the facing phosphorous (P) scarcity. The possible PR replacement with organic waste (OW), can be part of the solution to this problem, however few are the information about the plant P utilization efficiency following the utilization of recycled OW. In this light we have selected six OW: three anaerobic digestates (D1, D2, BD), two animal slurries (BS, SS), and one compost (MSWC). These were investigated for their main characteristics, P fractionation, and bio-available P during a 112 days pot test on ryegrass (30 mg P kg-

1 soil), in comparison with a chemical P source (KH2PO4, P-chem), in a nitrogen (N) non-limiting environment (200 mg N kg-1 soil). D1 and BD, showed the lowest P content (6 mg g-1), while D2 had 3-times higher P (18 mg g-1). Also the animal slurries (BS and SS) showed wide P range (8-33 mg g-1), while MSWC was at ≈5 mg g-1. Fig. 1 shows the P fractionation (%) from the tested product: labile P (H2O+NaHCO3), was similar in BD and BS (≈80)> D1 (60)> D2 (50)> SS (40)> MSWC (35).

Figure 1. Phosphorous fractionation in the tested products (left), apparent P recovery during the 112 days of pot test on ryegrass (center), and relationships between water extractable-P and plant P uptake (right).

Fig. 1 shows the best ARF (%) was registered in P-chem (20); amongst the OW the best was BD (19) = SS (18)> D1 (15) = LB (13)> D2 (9)> MSWC (2). The relative P utilization efficiency with respect to P-chem attained to >90% in BD and LS, then followed D1 and LB (70% and 60%), D2 reached 40%, and MSWC 10%. Anaerobic digestates and animal slurries can be valuable P sources for plant nutrition, their P availability in the short-medium time, can be reasonably described by the H2O-P

from P fractionation via a sigmoidal model of the type y =a

1+𝑒−(

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also the plant apparent utilization efficiency rapidly decrease over a threshold which can be determined by a combination of exceeding P and/or fixation in soil. Further investigation on the enzymatically hydrolysable P (from each fraction) are required to better understand potential available P after the utilization of this type of materials in soil.

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Environmentally and economically sound use of phosphorus in Flemish agriculture: determination of the critical soil phosphorus level

Stijn Martens1, Wendy Odeurs², Annemie Elsen² and Hilde Vandendriessche1,² 1Division of Crop Biotechnics, KU Leuven, W. de Croylaan 42, 3001 Heverlee, Belgium.

2Soil Service of Belgium, W. de Croylaan 48, 3001 Heverlee, Belgium.

Keywords: Critical phosphorus soil value, optimal zone Phosphorus is an essential nutrient which should be used more efficiently in the future. First of all phosphorus resources are non-renewable. On the other hand overfertilization resulted in to too high soil phosphorus levels in Flemish agricultural fields. This leads to eutrophication of surface water. Knowing that phosphorus stocks in Flemish agricultural fields are significant, the question rose from ecological point of view if the target zone for phosphorus in the soil should be lowered. Currently a P-AL (phosphorus in ammonium lactate, in mg / 100 g soil) range of 12-18 mg P-AL/100 g and 19-25 mg P-AL/100 mg are considered to be optimal for arable land and pasture, respectively (Tits et al., 2016). If the optimal zone would be lowered in Flanders, the impact on the yield should be minimal (>95% maximal yield). Recently critical soil phosphorus levels for yield reduction (Pcrit) were determined for important agricultural crops based on West and North European field trials (Nawara et al., 2017). In order to compare and validate these critical soil phoshorus levels for Flemish agricultural fields, a large set of field trials conducted by the Soil Service of Belgium since 1970 was used to calculate the Flemish Pcrit (as mg P-AL/100 g soil) were calculated for potato, sugar beet, maize, rye, barley, winter wheat and temporally grassland. Afterwards the Flemish Pcrit was compared to the West and North European Pcrit. The calculated Pcrit revealed that the soil pH has a significant influence on the phosphorus availability. In the case that only soil samples with a favourable pH were selected, the Pcrit decreased for every crop. The Pcrit of the complete dataset fluctuated between 5,9 and 16,4 mg P-AL/100 g for respectively winter wheat and maize. With a favourable pH the Pcrit fluctuated between 3,0 and 14,7 mg P/100 g for winter wheat and barley respectively. The obtained Pcrit deviated from the Pcrit in Nawara et al. (2017) due to differences in soil properties and a more extended dataset. This study shows that, when determining the critical soil phosphorus level, the different needs for phosphorus between crops, the influence of pH on the phosphorus availability and the combination of both should be taken into consideration. The P optimal zone should take the different Pcrits for different crops into account on a rotational level. References - Nawara S, Van Dael T, Merckx R, Amery F, Elsen A, Odeurs W, Vandendriessche H, McGrath S, Roisin C, Jouany C, Pellerin S, Denoroy P, Eichler-Löbermann B, Börjesson G, Goos P, Akkermans W, Smolders E (2017) A comparison of soil tests for available phosphorus in long-term field experiments in Europe. European Journal of Soil Science 68: 873-885. - Tits M, Elsen A, Deckers S, Boon W, Bries J, Vandendriesche H (2016). Bodemvruchtbaarheid van de akkerbouw- en weilandpercelen in België en Noordelijk Frankrijk (2012-2015). Bodemkundig Dienst van België, 218pp. D/2016/6537/01.

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Phosphorus x Nitrogen limitation in cropland at the global scale

Bruno Ringeval1, Marko Kvakić1,2, Laurent Augusto1, Philippe Ciais2, Xuhui Wang2, Daniel Goll2, Nicolas Vuichard2, Thomas Nesme1, Sylvain Pellerin1

1ISPA, Bordeaux Sciences Agro, INRA, 33140, Villenave d’Ornon, France.

2LSCE, LSCE/IPSL, CEA-CNRS-UVSQ, Universite Paris-Saclay, Gif-sur-Yvette, France.

Keywords: interaction phosphorus x nitrogen, nutrient limitation, cropland Besides water, P and nitrogen (N) are key limiting resources explaining the yield gap at the global scale. However, estimates of the contribution of each nutrient alone and together (PxN) to the global yield gap are currently lacking. Previous studies are either based on statistical approaches without distinction between P and N (Mueller et al. 2012) or are process-based but consider only one nutrient (Kvakić et al. 2018). Here we assess how much P, N and PxN limit maize, wheat and rice at the global scale through a process-based and spatially explicit modeling approach. We also investigate if the co-limitation is as frequent as found in natural ecosystems (Harpole et al. 2011). To do so, we confronted the nutrient demand (based on C:nutrient ratio and plant organs simulated by a global crop model without stress) and supply (potential P root uptake or N soil input) for each nutrient taken independently. The magnitude of the limitation in P and N is expressed through a supply:demand ratio (RP and RN respectively). Then, the effect of the interaction between P and N on the productivity is represented by two formalisms: based on the Liebig law of minimum or the multiple limitation hypothesis, leading to the computation of a supply:demand ratio RNP. We found that the N and P limitations are of the same order of magnitude at the global scale for each nutrient (RN~RP~0.5), but with a strong spatial heterogeneity (Figure 1). When considering N and P together, the supply:demand ratio (RNP) reaches 0.3. Increasing RNP to 0.7 requires an increase in N supply of 40-50% and in P supply of 30-35%. The choice of interaction formalism has almost no effect on the current nutrient limitation but a larger effect on the supply increase required to increase RNP. Finally, we estimated that a real co-limitation occurs in ~50% of the crop area. Although our study neglects plant adjustment to nutrient limitation (e.g. change in shoot:root ratio), it improves our understanding of the nutrient limitation in cropland and would also contribute to a better nutrient management at the global scale. References - Harpole WS, Ngai JT, Cleland EE, et al (2011) Nutrient co-limitation of primary producer communities. Ecol Lett 14:852–862. - Kvakić M, Pellerin S, Ciais P, et al (2018) Quantifying the Limitation to World Cereal Production Due To Soil Phosphorus Status. Glob Biogeochem Cycles. - Mueller ND, Gerber JS, Johnston M, et al (2012) Closing yield gaps through nutrient and water management. Nature 490:254–257.

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Solubility improvement of African local phosphate rock through calcination with potassium carbonate

Satoshi Nakamura1, Takashi Kanda1, Toshio Imai2, Sawadogo Jacques3, Fujio Nagumo1

1Japan International Research Center for Agricultural Sciences, 1-1 Ohwashi Tsukuba, Japan. 2Central Research Laboratory, Taiheiyo Cement Corp., 2-4-2, Osaku, Sakura, Japan.

3Centre National de la Recherche Scientifique et Technologique/Institut de l’Environnement et de Recherches Agricoles, INERA/Kamboinse, 01 BP 476 Ouagadougou, Burkina Faso.

Keywords: Burkina Faso, Fertilizer, Calcination Farmers in sub-Saharan Africa (SSA) has been struggling with high price of P fertilizer, while soils in this region has been faced P deficiency for crop production. It has been reported that P fertilizer price in SSA is extremely high compared with that of world average, although huge amounts of P resources, low-grade phosphate rocks (PRs), were found in this region. Therefore, affordable P fertilizer supply through utilization of African local low-grade phosphate rocks would contribute to strengthen crop production in SSA, and to improve farmer’s income. Authors have previously reported that solubility of African low-grade PRs can be enhanced by calcination under 900-1000 °C with sodium carbonate (Na2CO3) addition. Therefore, in this study, we aimed to improve a solubility of low-grade PR produced in Burkina Faso through calcination method with potassium (K) carbonate, and to evaluate the application effect of calcinated Burkina PRs (CB) on rice and maize. As a result, calcination with K carbonate increased 20 g L-1 citric acid solubility up to almost 100%, under the conditions of 900-1100 °C with 400 g kg-1 of K2O and 950-1100 °C with 300 g kg-1 and 350 g kg-1 of K2O. In the same calcination temperature, higher amounts of K2O gave higher solubility for 20 g L-1 citric acid. And water solubility indicated up to 39.4% at 900 °C with 400 g K2O kg-1 treatment. And the effects of CB application was evaluated in pot experiment. On the rice cultivation, above ground biomass yield in CB application was 1.8 g pot-1, while that in triple super phosphate was 3.6 g pot-1. Considering yields in non-P application and untreated Burkina PRs application, it can be considered that CB has an effect on rice growth. But its application effect is limited in the case of full-dose application. And in the case of maize, full-dose application of CB did not show significant effect. Authors concluded that it is possible to solubilize African low grade PRs through calcination with K carbonate, but further investigation will be required to have comparable effect with commercially available P fertilizer.

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Figure 1. Solubility change of Burkina Faso phosphate rock through calcination with several compounding rates of potassium carbonate under four levels of temperature

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Pathways to a sustainable use of phosphorus in Scottish food production Marc Stutter, Miriam Glendell1

1The James Hutton Institute, Craigiebuckler, Aberdeen. AB158QH, UK

Keywords: Phosphorus flows; national scale; agronomic P efficiency Whilst phosphorus is critical to food production, there are numerous socio-economic and environmental costs of its inefficient usage in agriculture. This has driven rules and guidance for improved targeting of P fertilizer applications to crops in interaction with different soil types. Since P issues link food, waste and environmental pollution aspects, it is beneficial to consider them as linked systems. Considering broad (e.g. national) systems, a sustainable P strategy requires understanding of the extent to which rock phosphate-based P inputs from agricultural production and human diets, as well as numerous ‘leakage’ pathways via wastes and runoff from the land, ultimately reach waters (a so-called ‘linear’ flow). Conversely, the minimization of losses from the system and opportunities for P reuse through P fertilizer replacement is often termed ‘closing the loop’. Such system appraisals highlight technical and other barriers that need addressing to join up parts of the system and encourage P recycling and reuse. Here we examine national-scale flows of P through agriculture and dominant waste streams for Scotland. This work aims to quantify the current P stocks and flows and opportunities to intercept materials capable of providing replacement for chemical P fertilizer. From this national context we then explore in detail the following key issues and challenges: (i) the current legacy of accumulating P in soils, its spatial distribution and how to make it more available to crop growth; (ii) understanding P availability, environmental loss risks and required tools (such as soil testing) associated with the use of waste streams (eg. sewage and anaerobic digestate) as soil amendments; and (iii) opportunities for the spatial coupling of locations of potentially-recyclable P materials with Scotland’s agricultural areas subject to constraints of current soil P status and P loss risk factors to inform national-scale planning.

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Enhancement in available phosphorus in soil with combined application of phosphorus fertilizer and organic matter derived from cattle manure compost

Taro Mishima1, Hiroka Tatori1, Masahiko Katoh1 1Department of Agricultural Chemistry, Meiji University, 1-1-1 Higashimita, Kawasaki,

Kanagawa, Japan.

Keywords: Cattle manure compost, combined application, phosphorus use efficiency Phosphorus should be effectively used for food production due to the limitation of phosphorus rock. One of the effective phosphorus use is the effective fertilization to suppress phosphorus immobilization and enhance the phosphorus use efficiency. An application of animal manure compost can suppress the phosphorus immobilization, however, its mechanisms is not fully understood. This study conducted some experiments to deeply understand how the soluble or insoluble organic matter (OM) of cattle manure compost retain or enhance the phosphorus mobility and availability. Brown fluvic soil and triple superphosphate was used as soil and phosphorus fertilizer, respectively. Soluble and insoluble OM of compost was obtained with the 1 M HCl-extraction and its residue, respectively. The column leaching tests of single or double soil layer were conducted. In the single soil layer test, four treatments were prepared: fertilizer, OM of compost, combined application, and no amendment. In similar, four treatments were prepared in the double soil layer test: upper : lower = OM : fertilizer, fertilizer : OM, no amendment : fertilizer, and fertilizer : no amendment. Pure-water was percolated, and the amount of phosphorus leached was estimated. The soil incubation test was also conducted at the same treatments of single soil layer column test. In addition, phosphorus sorption test using the insoluble OM was performed. In the phosphorus sorption test, the insoluble OM could not sorb phosphorus, suggesting that the insoluble OM of compost could not enhance or suppress the phosphorus availability. In the single soil layer test, the amounts of phosphorus leached were high at the following order: the combined application, fertilizer, OM, no amendment. The amount of phosphorus derived from fertilizer calculated by the subtraction was higher in the combined application than in the single application of fertilizer. This indicates that the presence of OM of compost could remain the phosphorus mobility in the soil at higher level. In the double soil layer test, the amounts of phosphorus derived from the fertilizer packed in the lower soil layer was higher than that packed

in the upper soil layer. This suggested that the soluble OM of compost can enhance the phosphorus mobility. On the basis of the incubation test, the contribution of soluble OM on the high phosphorus availability was supported. Figure 1: Phosphorus leached during the single soil layer column test. Combined: combined application, Fertilizer: single application of fertilizer, OM: single application of organic matter, NA: no amendment

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Long-term effects of biogas digestates application on phosphorus pools in soil and crop yield

Theresa Zicker1, Bettina Eichler-Löbermann1 1Chair of Agronomy, Faculty of Agricultural and Environmental Sciences, University of Rostock,

Justus-von-Liebig Weg 6, 18059 Rostock, Germany.

Keywords: Anaerobic digestion, soil P pools, crop yield Biogas digestates are nutrient-rich substrates and play an important role in agricultural nutrient cycles, especially for essential macronutrients like nitrogen (N) and phosphorus (P) (Bachmann et al., 2014). The objective of this study was to investigate long-term effects of application of biogas digestates compared to undigested substrates and a mineral NK treatment (without P) on soil and plant parameters under field conditions. The field experiment was established in 2008 in cooperation with a dairy farm. The input substrate (inputS) and the digested substrate (digestS) originated from the farm-owned biogas plant. The inputS mainly consisted of dairy slurry with an addition of maize silage and wheat. After 28 days of anaerobic digestion under mesophilic conditions the digestS was withdrawn from the fermenter. The substrates were applied in spring (20 m3 ha-1) and in autumn after harvest (10 m3 ha-1). The crop rotation consisted of maize, sugar beet, winter wheat, winter barley, and winter oilseed rape. Soil samples were taken four times per year in the top soil and subsoil. Soil P concentrations and the degrees of P saturation (DPS) were higher in the inputS and digestS treatments compared to control without P, but no significant differences between inputS and digestS application were found. In the subsoil, however, application of the digestS resulted in highest P concentrations and DPS values. On average over the experimental years the application with inputS and digestS resulted in higher crop yields and P uptakes compared to the NK treatment, whereat no differences between the inputS and digestS treatments were found. Our results indicated that biogas digestates have a similar fertilizer effect as undigested slurries fertilizers but may increase the risk of P losses due to higher P concentrations in the subsoil. References - Bachmann S, Gropp M, Eichler-Löbermann, B (2014) Phosphorus availability and soil microbial activity in a 3 year field experiment amended with digested dairy slurry. Biomass and Bioenergy 70:429-439

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Phosphorus recovery from urine using Layered Double Hydroxides Kris Dox1, Maarten Everaert1, Erik Smolders1

1 Division of Soil and Water Management, Department of Earth and Environmental Science, KU Leuven, Kasteelpark Arenberg 20, B-3001 Heverlee, Belgium.

Keywords: Layered double hydroxide (LDH), phosphorus, adsorption, recovery, urine, X-ray diffraction (XRD)

In this study, the potential of Mg/Al or Zn/Al layered double hydroxides (LDHs) for Phosphate (P) recovery was assessed. Urine contains sufficient P that can be recycled. The LDHs are anion exchangers and P-loaded LDHs have demonstrated fertilizer potential. The most important obstacle for efficient recycling is to obtain stable crystals that are not degraded by the citrate complexing Al3+ and by dissolution at the low pH of the urine. Phase pure ZnAl- and MgAl-LDHs were synthesised at different pH, at different Mg/Al or Zn/Al ratio and were exchanged with P from different adsorption solutions, with or without citrate and including synthetic urine. The P uptake increased for LDHs containing lower Mg/Al ratios and synthesised at lower pH and for sorption solutions at lower pH. These trends are explained by increased anion exchange capacity (AEC) and by P speciation (charge) in the LDHs, XRD spectra confirm this interpretation. The P capacity reached 61 mg P/g LDH which is 85% of the theoretical LDH capacity and only 1 g LDH is required to remove 90% of P/L urine. The Zn/Al LDHs have equal P uptake efficiencies compared to the MgAl-LDHs but yielded more irreversible sorption. In contrast, the Mg/Al LDHs had high desorption yields (53 mg P/g). A high potential of MgAl-LDHs for P recovery from urine is supported.

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Long-term economics of placing phosphorus at depth in modern farming systems

Andrew Zull1, Howard Cox1, Jayne Gentry1, James Hagan1, David Lester1, Mike Bell2 1Queensland Department of Agriculture and Fisheries, Crop and Food Science, 203 Tor St

Toowoomba (4350), Queensland, Australia 2The University of Queensland, School of Agriculture and Food Sciences, Gatton (4353),

Queensland, Australia.

Keywords: Economics, decision support tool, sub-soil Amelioration Following more than 20-years of broad-acre no-till farming, it is estimated that up to a million hectares of grain growing land across Australia's Northern Grains Region (Queensland and New South Wales) are currently at risk of subsoil (10-30cm) phosphorus (P) deficiency. Researchers have identified potential yield benefits from replenishing P in deficient sub-surface layers, however with upfront costs of amelioration typically exceeding $100/ha growers were unsure whether it was economical. A bio-economic model was developed and ground-truthed via six case studies with growers from across the region, and against trial data being generated by soil nutrition researchers. We found that it was possible to predict yield responses with high accuracy (R2=0.98), meaning the model was likely to be helpful for growers in making deep-P decisions. Thus the model was developed into an online decision support tool (Deep-P Calculator).

Figure 1: Parameters of the Deep-P model, which identifies the economics of placing phosphorus at depth.

The economic threshold (based on a Colwell-P and BSES-P soil analysis) and optimal rate of deep-P is driven by crop yield potential, crop responsiveness and deep-P costs; however, the calculator typically suggests deep-P amelioration is economic when Colwell-P ≤ 8mg/kg in the 10-30cm layer and BSES-P is <100. The calculator normally suggests a 2-year payback period for a deep-P rate of 20 to 30 P kg/ha and this corresponds well with trial results.Despite an imperfect understanding of soil P behavior, when paired with research trials and case studies, modelling was capable of providing valuable information to decision makers on the benefits of ameliorating P deficient sub-soils in this region.

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Animal manure and mineral fertilizer are equally effective sources of phosphorus for maize in the long term

Jingying Jing, Julie T. Christensen, Bent T. Christensen, Peter Sørensen, Gitte H. Rubæk. Department of Agroecology, Aarhus University, Blichers Allé 20, P. O. Box 50, DK-8830 Tjele,

Denmark Keywords: P water extraction, maize, long-term study

Efficient recycling of phosphorus (P) is crucial to minimize the adverse environmental problems caused by over-application of P fertilizer to cropland. Short-term pot experiments often show that organic amendments provide plants with more P than unfertilized soil but with less P than mineral fertilizer. However, long-term experiments with repeated additions are essential for investigating the value of P applied in animal manure versus P added in mineral fertilizer. This study examines the effect of long-term application of mineral fertilizer and manure on soil P availability and maize plant growth.The study was based on the Askov Long-term Experiment on Animal Manure and Mineral Fertilizer (Askov-LTE), established in 1894. The main treatments are unfertilized plots (0) and plots fertilized with three levels (½, 1 and 1½ times the standard rate for a given crop) of nitrogen (total N), phosphorus and potassium (K) applied in mineral fertilizer (NPK) or in animal manure (AM). We measured total P and water extractable P (Pw) in soil, and plant height, dry weight, P concentration, P uptake and final yield of silage maize grown on the plots. Long-term fertilization significantly increased Pw and soil total P compared with unfertilized plots but NPK and AM treatments receiving identical doses of P did not differ. Compared with NPK, maize growth in AM plots was significantly improved. On average, AM application increased plant dry weight by 23%, plant P concentration by 8%, plant P uptake by 31% at 3rd of August, and final yield by 13% compared with comparable NPK treatments. Fitting the data with the Mitcherlich equation confirmed a strong relationship between plant growth and Pw (Fig.1). We found similar effect of long-term application of AM and NPK on soil P availability based on Pw measured in soil. However, maize plants grew better on soil with long-term AM application. This is probably due to increased organic matter content and extra nutrient reserves other than P in the AM treated soil. Long-term application of P in AM contributes to soil P availability equally to P applied with mineral fertilizers and it enhances maize plant growth compared with NPK application. Pw appeared to be a good indicator for predicting the response of maize to long-term P additions.

Figure 1: Effect of long-term NPK and AM application on final yield of maize (a) and relationship

between Pw and final yield (b).

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Increasing the P use efficiency in soilless cultivation by reducing or reusing the P exported with spent growing media

Bart Vandecasteele1, Fien Amery1, Tom Van Delm2, Nele Ameloot3, Rian Visser4, Jane Debode1

1Institute for Agricultural and Fisheries Research, Plant Sciences Unit, Burg. Van Gansberghelaan 109, 9820 Merelbeke, Belgium,

2Proefcentrum Hoogstraten, Voort 71, B-2328 Hoogstraten, Belgium, 3Greenyard Horticulture Belgium NV, Skaldenstraat 7a, 9042 Gent, Belgium,

4TNO, Energy Research Center of the Netherlands, Westerduinweg 3, 1755 ZG Petten, The Netherlands

Keywords: Circular horticulture, peat replacement, nutrient recycling

Recycling of P and other nutrients in spent growing media at the end of soilless cultivation is crucial in the framework of circular horticulture. Two aspects were considered in this study: (a) the effect of fertigation and growing medium formulation on nutrient accumulation in the growing medium during the culture, and (b) the use of spent growing media as bulking agent for composting or feedstock for biochar production. Growing media formulation and fertigation strategy strongly affect the characteristics and nutrient content of the spent growing media. Four years of greenhouse trials with strawberry grown on compost- or peat-based growing media revealed that strawberry plants made highly efficient use of the P and K in the compost when P and K input by fertigation was reduced. In contrast, the nutrients supplied by fertigation but not used by the plants in the peat-based substrates with regular fertigation, accumulated in the substrates and were removed with the spent substrate at the end of the culture. Peat-based growing media with conventional fertigation had an average net accumulation of 65 kg P and 80 kg K in the spent growing media per ha greenhouse. The use of compost as a source of nutrients allows for alternative nutrient supply of at least 20 kg P and 120 kg K per ha greenhouse. The focus of the Interreg 2 Seas Horti-BlueC is now on further fine-tuning of fertigation and on the added value of biochar and compost in growing media to increase the P use efficiency. Recycling of these nutrients and the organic matter in the spent growing media at the end of the culture is another step towards a more sustainable cropping system, i.e., by composting or biochar production and reuse of these materials in agriculture. In Interreg 2 Seas Horti-BlueC we will adapt the cultivation conditions to optimize the value of spent growing media as feedstock for biochar and compost.

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Current versus future scenario for spent growing media, by reducing or reusing the exported P as part of circular horticulture

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Effect of phosphorus and locations on grain yield of different small fab

bean varieties (Vicia faba minor) Khalid Daoui1, Hind. Masaad2, Mohammed Karrou 1, Rachid Mrabet1, Zain El Abidine Fatemi1,

Mustafa Ouknider3 1National Institute of Agricultural Research Morocco (INRA. Morocco).

2National School of Agriculture of Meknès (Morocco)

Key words: Vicia faba minor, Phosphorus Faba bean (Vicia faba L.) is the most important pulse crop grown in Morocco. Due to its N2 fixation capacity and its beneficial effect on soil structure faba bean is appreciated in rotation with cereals. However, this crop is mainly grown by small farmers and its productivity is low and variable because of rainfall scarcity and variability and because of traditional agricultural practices especially low fertiliser application. The aim of this work is to providing farmers with genotypes adapted to specific conditions of phosphorus availability in the soil and having good phosphorus use efficiency should improve yields, without increasing excessively production cost or damaging the environment. Two trials were conducted under field conditions in two different locations: (L1, P2O5 (Olsen)=29,23 ppm ) and (L2, P2O5 (Olsen)= 32,38 ppm). In this trials, three Moroccan faba bean varieties (V) (Vicia faba minor) Alfia 5, Alfia 17 and Alfia 21 were combined with four phosphorus (P) rates (0, 20, 80 and 160 kg P2O5/ha). The experimental design was a split plot with four replicates where P was affected to main plots and variety to sub plots. At maturity, yield and its components have been measured. Under L1 conditions, P application had significant effect on grain yield but V and P* V had no significant effects. Applications of 20 and 80 kg P2O5 /ha increased yield respectively by 21 and 34% comparatively to check. While application of 160 kg P2O5/ha induces 9% of yield decrease comparatively. In location 2, no P, no V no P*V had significant effect on grain yield. In L1, main grain yield reach is 21,26 qx/ha while in location 2, main grain yield achieved was 12,41 qx/ha. Grain yield achieved in both locations should have been limited by low rainfall received (278 mm in L1 and 265 mm in L2). While grain yield achieved differences between L1 and L2 may be explained by soil texture differences in L1 soil was a vertisol with great capacity of water storage comparatively to L2 witch contain less clay. Those conditions may explain also significant impact of phosphorus application under L1 comparatively to L2. The negative impact of increasing P application on faba bean grain yield in L1 may be explained by P antagonism effect with Zn nutrition. Even the experimentation should be conducted under other conditions of soil P availability and rainfall conditions we noted that in L1, the combination, (Alfia 17- 80 kg P205/ha) give the best yield while under L2, no difference had been shown probably due to grain yield limitation.

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Potential of nursery phosphorus micro-dosing in lowland rice production in Madagascar

Seheno Rinasoa1, Tovohery Rakotoson1, Yasuhiro Tsujimoto2, Lilia Rabeharisoa1, Matthias Wissuwa2

1Laboratoire des Radio-Isotopes, Université d’Antananarivo, Route d’Andraisoro B.P. 3383, Antananarivo 101, Madagascar.

2Japan International Research Center for Agricultural Sciences (JIRCAS), Crop Production and Environment Division, Ohwashi, Tsukuba, Ibaraki, Japan

Keywords: Phosphorus, micro-dosing, nursery management

Phosphorus (P) remains one of the factors limiting rice production in Madagascar which is attributed to its deficiency in most of the Central Highlands ’paddy fields and the low to non-use of fertilizers. Sustainable P management is required in order to overcome this problem given high cost of mineral fertilizers and their non-availability among smallholder farmers. It was recently shown that the application of a micro-dose of P in nursery bed substantially enhanced seedling vigor and subsequent grain yield of transplanted rice at low P availability. This study evaluated the potential of such P microdosing in a P-deficient lowland field in Madagascar. Rice was sown in a nursery bed with six treatments; a non-fertilized control compared to 5 different sources of P, each applied at a rate of 6 g P/m2: triple superphosphate (TSP), rice bran (RB), vermicompost (VC), guano (GU) or NPK. Four week old seedlings were transplanted to main plots with the following fertilizer treatments: P, NK, NPK (P applied at 25 kg P/ha) and a non-fertilized control. In the nursery, NPK, VC and GU improved seedling weight by 235, 70 and 109%, respectively, and root weight by 250, 50 and 35% over the non-fertilized control at the time of transplanting. Seedling P uptake was highest in NPK (0.246 mg/plant) which was at least 4.8-fold above the other treatments. Tissue P concentrations in seedlings from the TSP treatment was as high as that of NPK (> 0.3%), however, biomass did not increase significantly over the control, possibly due to severe co-limitation of growth by N. After transplanting to main plots, no clear effect of nursery treatments was observed on grain yield for the non-fertilized control and P treatments, even for seedlings from the NPK treatment despite their high P content. A positive nursery treatment effect on grain yield was detected in the main plot NK and NPK treatments, where seedlings not receiving P in the nursery had delayed maturity and a reduction in grain yield of up to 55%. Our results suggest that in environments where growth is co-limited by N and P availability, nursery P supply allows plants to better utilize N applied after transplanting. To achieve high yields either NPK application to the main field, or NK application to the main field in combination with P application to the nursery is required. In addition to mineral P fertilizers, VC and GU are potentially good native P sources available to smallholder farmers.

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Improving the ecological role of grain legumes in Mediterranean intercropping systems: root exudation to exploit phosphorus from the soil

Emilio Lo Presti1, Beatrix Petrovicova1, Maurizio Romeo1 e Michele Monti1 1Department AGRARIA, University Mediterranea, Reggio Calabria, Feo di Vito 89122 Reggio

Calabria, Italy.

Keywords: Intercropping, phosphorus, sustainable Intercropping enhancing agro-biodiversity could play an essential role in sustainable intensification to improve the sustainability of cropping systems in a context of low external inputs and unpredictable climate change (Costanzo and Bàrberi, 2014). In intercropping some facilitations at rhizosphere level occur, as nutrients availability improvement, depending on root exudates that can play a role of ecological tool. In a grain legume/cereal intercrop the legume root exudates (carboxylates and phosphatases) are involved in phosphorus (P) soil availability that represents a facilitation for the cereal (Li et al., 2016). The aim of this research is to evaluate the legumes for nutrients uptake improvement in Mediterranean semi-arid conditions focusing the attention to P availability. Under controlled environment wheat, lupin, faba bean and pea were grown in pot as sole crop and in intercrop combining each legume with durum wheat at two levels of phosphorus soil supply: natural content in soil (P0) and adding 50 mg of phosphorus per kg of soil (P1). Crop growth in both sole crope (SC) and intercropping systems (IC) was interrupted at the full flowering stage of single legume species when, soil and plant sampling were carried out. In soil were measured pH, total N and C, NH4+, NO3--, P (total, mineral, organic and available fractions), the quantity and quality of carboxylates exuded and acid phosphatase activity were determined. Shoot and root dry matter accumulation were accounted and C, N and P concentration in tissue were measured separately. Data showed that, compared to SC, IC absorbed phosphorus more than sole crop when no phosphorus was added and a significant contribution of wheat, especially in pea and lupin IC (56 and 61% of total P amount in mixture respectively), was highlighted. Among IC, wheat/pea absorbed phosphorus much more efficiently than other mixtures also due to high contribution of pea. With low phosphorus soil availability wheat intercropped with pea showed a significantly higher P uptake than SC (142 and 95% more in P0 and P1 respectively). Phosphorous uptake by intercropped wheat was related to phosphatase activity in the rhizosphere. Conclusions: Our results show that, under low available phosphorus condition, the root facilitation in intercropping with legume is beneficial to wheat P-uptake and this is added to the benefit produced by N fixation in increasing N mineral soil availability. References - Costanzo A, Bàrberi P (2014) Functional agrobiodiversity and agroecosystem services in sustainable wheat production. A review. Agronomy for Sustainable Development 34:327-348. - Li C, Dong Y, Li H, Shen J, Zhang F (2016) Shift from complementarity to facilitation on P uptake by intercropped wheat neighboring with faba bean when available soil P is depleted. Scientific Reports 6, 18663.

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Deep-placing phosphorus in NE Australian grain soils: 2. Influence of P rate x band spacing (and form) on crop yield

David W. Lester1, Michael J. Bell2, Duncan J. Weir1, Douglas Lush1 1Queensland Department of Agriculture and Fisheries, Toowoomba, QLD 4350 Australia.

2University of Queensland, Gatton, QLD 4343 Australia.

Keywords: Deep-placement, P band spacing, P rate An experimental program across regional Queensland (16 sites) has demonstrated increased grain crop yield (5-30%) with placing fertiliser P at ≈0.2m depth on ≈0.5m band spacing (Lester et al. 2018). Recovery of fertiliser P by roots is a diffusion driven process, so in-band P concentrations will affect rates of P supply to roots. In-band concentrations are a function of i) the P application rate, and ii) the lineal meters/ha (fertiliser band spacing). Crop recovery will be influenced by the roots interacting with P bands (the number of bands/ha) and the rate of diffusive supply from bands to crop roots around them (in-band concentration and root proliferation). Two experiments were established to research how the interaction of P rate and P band spacing changed crop response to deep placement. Rates applied were 0, 10, 20, 40 and 80 kg P/ha. Experiment (Exp) 1 had an incomplete factorial of 0.25, 0.50 and 1.00 m band spacing with mono-ammonium phosphate (MAP: 10N 22P) as the P source. Experiment 2 was a full factorial of 0.25, 0.50 and 1.00 m band spacing as main-plots, with a split-plot comparing granular MAP and a fluid MAP (10N 15P) as the P sources. Both experiments had 6 replicates, with grain yield and P uptake at maturity measured. Exp 1 has had three crops harvested (barley in 2015, cotton in 2016-17 and barley in 2017) while Exp 2 had a first crop of chickpea in 2017. Only Exp 1 2015 barley and Exp 2 2017 chickpea have recorded significant treatment responses, with yields responding to P rate (Table 1), but not to band spacing or product (data not shown).

Table 1 – Mean grain yield ± standard error (kg/ha) with deep-placed P rates

kg P/ha

Experiment/Crop 0 10 20 40 80

Exp 1 2015 Barley 4434±42 a 4483±51 a 4790±45 b 4696±42 b 4700±73 b

Exp 2 2017 Chickpea 1753±36 a 1937±36 b 2065±36 c 2155±36 cd

2227±36 d

Letter represented l.s.d. at 5% level

Resolving interactions between P rate and band spacing are challenging in field experiments. Seasonal conditions (low rainfall) have limited responses in two of four site years, through reduced crop P demand, although both sites were P responsive with favorable growing conditions (Table 1). Expectations that pulse species with coarser root systems were more likely to respond to closer band spacing than fibrous-rooted cereal crops were not supported. Research to fine-tune deep fertilizer application strategies is continuing. References Lester DW, Bell MJ, Sands DJ (2018) Deep-placing phosphorus in NE Australian grain soils: 1. Cumulative grain yield increased by 5-30%. PSP6 Symposium on Phosphorus in Soils and Plants, Leuven (BE).

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Deep-placing phosphorus in NE Australian grain soils: 3. Model to establish critical surface and subsurface values for P soil testing

David W. Lester1, Kerry M. Bell1, Michael J. Bell2 1Queensland Department of Agriculture and Fisheries, Toowoomba, QLD 4350 Australia.

Keywords: Deep placement, subsoil P, soil testing Placing phosphorus (P) fertiliser at ≈0.2m depth has increased crop access to applied P, boosting cumulative yield of grain crops by 5-30% over 4+ years in north-eastern Australia's cropping zone (Lester et al. 2018). Fertilizer advisory services use critical soil test concentrations to identify fields where fertiliser P responses are likely, but such values have not been defined for grain or pulse species accessing multiple soil layers (e.g. surface 0.0-0.1m and subsurface 0.1-0.3m). To define critical values for interacting soil layers, a different research methodology is required. A 3-D (XYZ) matrix of surface (X) and subsurface (Y) labile P concentrations should allow generation of a response surface for yield of species (Z). While not a full factorial model, Table 1 of 72 plots allows contrasting regression equations between i) increasing surface labile P concentration at two subsurface P concentrations, and ii) increasing subsurface concentrations at two surface P concentrations. Measurement intensity, indicated by numbers of plots in each XY combination, is higher at lower soil test concentrations for more precise measurement. This framework is being deployed with two or three crop species grown simultaneously (in different blocks) allowing relative responsiveness to labile P concentration to be compared across species i.e. spring wheat vs chickpea. Soil test P concentrations will decline with time, but a wide range of initial target concentrations should ensure a series of crop cycles under different seasonal conditions can be assessed.

Table 1: Surface and surface treatment matrix, cell numbers represent plots.

Surface treatment number (X)

Subsurface treatment number (Y)

Soil P (mg/kg)

1 2 3 4 5 6 7

10 15 20 25 30 40 60

1 2 6 4 4 3 3 3 3

2 5 5 3

3 8 4 4 3 3 3 3 3

4 12 4 3

5 20 2 2

6 30 2 2

Treatments can be arranged in row-column (e.g. 8x9) design with a blocking structure to meet site variability and logistical access requirements. Field establishment has been achieved using precision earthmoving equipment to remove the 0.0-0.1m layer, allowing access to the 0.1-0.3m layer for treatment. Fluid P is sprayed onto the soil to ensure an even spatial distribution, after which the

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profile layer is thoroughly mixed with tillage to distribute the applied P through the layer. The surface 0.1m of soil is then returned and the same application/incorporation methods used to generate the surface P concentration range. References

- Lester DW, Bell MJ, Sands DJ (2018) Deep-placing phosphorus in NE Australian grain soils: 1. Cumulative grain yield increased by 5-30%. PSP6 Symposium on Phosphorus in Soils and Plants, Leuven (BE).

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Phosphorus Efficient Cereals: Is Genetic Engineering of Plant Phosphorus the Answer?

Beverly Agesa1, Paul Withers1, Katherine Steele1, Victor Raboy2 1School of Environment, Natural Resources and Geography, Bangor University, LL57 2UW,

Wales, United Kingdom. 2 USDA-ARS, Small Grains and Potato Germplasm Research Unit, 1691 South 2700 West, Aberdeen, ID 83210, United States

Keywords: Low P mutants, PUE, Genetic improvement

Most research addressing phosphorus (P) efficiency in plants has focused on understanding and enhancing the ability of plants to take up soil P, rather than utilizing nutrient P more efficiently within the plant (Vandamme et al., 2016). With the increasing global demand for P, diminishing phosphate rock resources and the adverse environmental impacts on water quality and related ecosystem services due to P leakage in the food chain, there is a need for more innovative and diverse solutions to enhance Phosphorus Use Efficiency (PUE) in crop production. Only a small proportion of the total P taken up by the plant (50-90 kg P2O5/ha) is actually required for plant metabolism and mass P storage in plant tissues typical of modern varieties grown on P-rich soils may be unnecessarily depleting critical phosphate rock resources and impairing water quality (Withers et al. 2014). This study explores the feasibility of reducing P concentrations in the grain of barley and wheat by genetic improvement through mutation of target genes involved in the phytic acid metabolic pathway. Possible reductions in crop P requirements of up to 25% have been suggested for P-efficient cultivars with low P mutants having been identified in barley (lpa1-1) showing both good yield performance and reduced seed total P content (Raboy et al., 2015). This study seeks to understand the growth, crop performance and P metabolic requirements of low P-efficient mutants of barley and wheat cultivars under different soil P environments using quantified laboratory and field experiments to aid selection of suitable lines for commercial breeding. In addition, CRISPR-gene editing of the target gene is being tested in barley. An initial screening of an M3 population of >3200 barley low P mutant lines (lpa 1-1) suggested that a P trait for low grain P concentration is indeed heritable with P concentrations of < 3mg/g as compared to wild type barley (4.5mg/g) recorded. The poster will also describe pot experiments testing the growth and performance of barley low P mutant lines (lpa 1-1) and wild type barley in low soil P and high soil P environments, and in the presence or absence of applied inorganic P fertilizer to assess seed vigor, crop growth and plant P metabolism/uptake. A reduction in grain P concentrations due to improved plant PUE will reduce the amount of P fertilizer required for crop production allowing a “slowdown” in global P cycling and reduced eutrophication risk. References

- Raboy, V., Peterson, K., Jackson, C., Marshall, J. M., Hu, G., Saneoka, H., & Bregitzer, P. (2015). A substantial fraction of barley (Hordeum vulgare L.) low phytic acid mutations have little or no effect on yield across diverse production environments. Plants, 4(2), 225-239. // Vandamme E., Wissuwa M., Rose T., Ahouanton K., & Saito K. (2016). Strategic phosphorus (P) application to the nursery bed increases seedling growth and yield of transplanted rice at low P supply. F. Crop. Res. 186, 10–17. //Withers, P. J. A., Sylvester-Bradley, R., Jones, D. L., Healey, J. R. & Talboys, P. J (2014). Feed the crop not the soil: Rethinking phosphorus management in the food chain. Environ. Sci. Technol. 48, 6523–6530.

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The effect of application of citrus fruit on phosphorus availability in soil amended with cattle manure

Cecilia Paredes1, Siobhan Stauton2 and María de la Luz Mora3 1Doctoral Program in Science of Natural Resource, Universidad de La Frontera, Temuco, Chile.

2INRA, UMR Eco&Sols, Ecologie Fonctionnelle et Biogéochimie des Sols et des Agrosystèmes,INRA-IRD-Cirad-SupAgro, Place Viala, 34060 Montpellier, France.

3Center of Plant, Soil Interaction and Natural Resources Biotechnology, Scientific and Biotechnological Bioresource Nucleus, Universidad de La Frontera, Temuco, Chile.

Keywords: Citrus fruit; phosphorus release, cattle manure

Nowadays, phosphorus (P) recovery and recycling have a vital importance to enhance soil fertility and provide food security. Waste like cattle manure has been mainly used as source of nutrients particularly P, in organic agriculture. On the other hand, organic acids such as citric, malic and oxalic, can solubilize phosphate, and these types of organic acids can be found in citrus. The aim of this study was to assess the effect of lemon fruit application to soil amended with cattle manure on P release (Figure 1A), pH and acid phosphatase activity. An incubation experiment was set up for soil, which were amended with cattle manure (Cm) at 1% and 5% rate and lemon treatments with 20 or 40 % of peel (LP); 40% of juice (LJ) and 40% whole fruit (WF). Soil without Cm was designated as the control.

Figure 1. A. Graphical abstract of the study. B. Inorganic phosphorus concentration from incubation at 1 hour sampling time.

Treatments with 5% Cm and 40% WF reached the highest phosphate concentration, with a value of 1161 µg kg-1 (Figure 1B). The application of 40% LP also caused an increase in the soil P concentration, both for the unamended and amended soil; whereas in the LJ treatment, the lowest concentrations were obtained. As compared with soil control, treatments with LP and WF significantly increase the phosphatase activity after 1 hour of incubation reaching values above 100 nmole PNP min-1 g soil-1. However, a significant decrease from 60 to 40 nmole PNP min-1 g soil-1 when LJ treatment was observed. On the other hands, treatments with 20% and 40% LP after 1 hour of incubation showed a decreased of 0.8 and 0.9 units of pH respectively respect to control in unamended soil. In conclusion, the use of Cm and lemon fruit had a beneficial effect on P concentration and phosphatase activity in soil, indicating that both are beneficial to the soil biota and can help to improve soil fertility and sustainability of agricultural production system.

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Overuse of phosphorus fertilizer reduces the grain and flour zinc bioavailability of intensive winter wheat production

Chunqin Zou, Wei Zhang

College of Resources and Environment, China Agricultural University, Yuanmingyuan West Road

2, 100193 Beijing, China

Keywords: Zinc, Bioavailability, Phosphorus Studies have focused on the negative effects of phosphorus (P) application on the Zn concentration in the whole grain, but few assessed the effects of P application on the protein, Zn, Fe, Mn concentrations in milled products. Determination of protein, Zn concentrations and bioavailability in different milled products would be beneficial for humans to supplement Zn in the diet. A field trials consisted of six P application rates in a winter wheat–summer maize rotation system. Each treatment had four repetitions. The P application rates were: 0, 25, 50, 100, 200 and 400 kg P /ha. The grain yield increased with P application but did not further enhance when P rates exceeded 50 kg/ha. As P application increased, the protein concentration in grain and standard flour and the viscosity of standard flour decreased. Phosphorus and phytic acid concentration in grain and flours increased and then plateaued, while Zn concentration decreased and then plateaued as P application increased from 0 to 100 kg/ha. Estimated Zn bioavailability in grain and flours decreased as P application increased from 0 to 100 kg/ha and then plateaued. Estimated Zn bioavailability was greater in standard flour, bread flour, and refined flour than in grain or coarse flour because the concentration of phytic acid is higher in the bran and coarse flour. Meanwhile, P application decreased the concentration of Cu but did not significantly affect the concentrations of Fe and Mn in grain and flour. The concentrations of Cu, Fe and Mn were higher in grain and coarse flour than in the other flours. In conclusion, Phosphorus supply in the intensive cropping of wheat can be optimized to simultaneously obtain high grain yields, high grain and flour protein, and high Zn bioavailability. References - Zhang Y Q, Deng Y, Chen R Y, Cui Z L, Chen X P, Yost R, Zhang F S, Zou C Q (2012) The reduction in zinc concentration of wheat grain upon increased phosphorus-fertilization and its mitigation by foliar zinc application. Plant and Soil 361, 143-152. - Miller L V, Krebs N F, Hambidge K M (2007) A mathematical model of zinc absorption in humans as a function of dietary zinc and phytate. Journal of nutrition 137, 135-141.

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Zinc nutrition of wheat in response to application of phosphorus to a calcareous soil and acid soil

Xiu-Xiu Chen, Wei Zhang, Chun-Qin Zou* College of Resources and Environment, China Agricultural University, Beijing, China

Keywords: Soil type, Soil available Zn, Zn nutrition, Wheat Although phosphorus (P) application is known to affect the zinc (Zn) nutrition of crops, the underlying mechanisms and effects of soil type are unclear. A greenhouse pot experiment was conducted with wheat, two soils (calcareous and acid), and nine P fertilizer rates (0, 50, 100, 200, 400, 1000, 2000, 3000, and 5000 mg P2O5 kg-1 soil). The effects of P application on the Zn content of shoots and roots in wheat and on the levels of available Zn in soil differed on the acid soil and calcareous soil. The shoots dry weight of wheat on both soils was highest with 2000 mg P2O5 kg-1. The total Zn accumulation in wheat reduced from 2000 mg P2O5 kg-1 on the acid soil and from 100 mg P2O5 kg-1 on the calcareous soil. Available soil Zn declined when the soil Bray-P concentration increased to 34 mg kg-1 in the acid soil and when the Olsen-P concentration increased to 196 mg kg-1 in the calcareous soil (Fig. 1). Shoots Zn nutrition was negatively related to available soil P on the two soils.The negative effects of P application rate on Zn nutrition of wheat differed between the two soils. The decreased effects of P application on Zn nutrition of wheat were not due to available soil Zn under the condition of current agricultural practices.

Figure 1: Effects of available soil P concentration on the concentration of available soil Zn.

y = 9.7228e-2E-04x

R² = 0.40***

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co

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(c)

y = 0.0002x2 - 0.04x + 9.68

R² = 0.38***

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y = 5.19e-4E-04x

R² = 0.89***

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Identifying critical phosphorus concentration to optimize population establishment and physiological traits and maximize yield of winter wheat

Xiu-Xiu Chen, Chun-Qin Zou Center for Resources, Environment and Food Security, China Agricultural University, Beijing,

100193, People’s Republic of China

Keywords: Phosphorus, Population development, Winter wheat The aims of this study were to identify the critical P concentration in wheat to optimize population development and tiller quality of winter wheat, and determine the response of LAI and Pn of winter wheat to P application to maximize the grain yield. A 3-year field experiment with six P application rates ranging from 0 to 400 kg P ha-1 was conducted. Treatment were arranged in randomized complete block design with four replicates. The quantity and quality of wheat population, net photosynthesis rate (Pn) and leaf area index (LAI) of wheat were significantly affected by P application rate. At stem elongation stage, shoot P concentration of 2.8 g kg-1 was the threshold to increase tiller number (Fig. 1). Meanwhile, critical P concentration of 2.4 g kg-1 in main stem (MS) and 3.7 g kg-1 in tiller 1 (T1) promoted the maximum development of MS and T1. At anthesis stage, P critical levels for MS and T1 development were 2.0 and 3.4 g kg-1, respectively. In general, shoot P concentration of 2.0-2.4 g kg-1 at anthesis stage resulted from 15-20 mg kg-1 soil Olsen-P concentration can achieve the optimal spikes, Pn, LAI, and biomass, and then optimize the grain yield of winter wheat. Optimal P application could integrate the development of population quantity, quality, Pn, and LAI of winter wheat synchronously. Figure 1: Schematic diagram of phosphorus utilization process about coordinating spikes and shoot biomass of winter wheat

86 65

41 45

87 ﹥400

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34 20 2015

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- +

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Phosphorus response and utilization in two ornamental crops Siri Caspersen, Karl-Johan Bergstrand

Department of Biosystems & Technology, Swedish University of Agricultural Sciences, SE-230 53 Alnarp, Sweden

Keywords: chrysanthemum, phosphorus utilization efficiency, poinsettia Limited availability of phosphorus (P) has been suggested as a potential method for restricting shoot length and improving drought stress tolerance and post-harvest quality of ornamental plants. At the same time, improved synchronization of substrate P availability with plant requirement could minimize unnecessary use of P fertilizers in horticultural plant production, limiting the risks of P leakage and eutrophication and improving the use efficiency of a non-renewable resource. The aim of the present study was to investigate the possibility of using a restricted supply of P for controlling shoot length of poinsettia and chrysanthemum, as an alternative to the use of chemical plant growth regulators. In a greenhouse pot experiment, we investigated the effect of restricted P fertilization on shoot length and biomass production, plant development, phosphorus uptake and utilization for poinsettia (Euphorbia pulcherrima cv. ‘Mira Red’) and chrysanthemum (Chrysanthemum morifolium cv. ‘Breeze Cassis’). The peat-based substrate was fertilized with 6, 12, 18, 24 or 48 mg P per L at the start of the experiment, and the same P concentrations were also added as weekly fertigation during the latter part of the growing period. Shoot length was significantly reduced at 6 mg P L-1 only. However, chrysanthemum flower bud number and poinsettia bract number, as well as lateral shoot numbers, were also reduced by low levels of P fertilization. Phosphorus utilization efficiency rapidly decreased with an increasing level of P fertilization, and above 12 (chrysanthemum) or 24 (poinsettia) mg P L-1, further addition of P did not lead to further increases in shoot biomass. As shoot length was significantly restricted at the same P level as bud (chrysanthemum) and bract (poinsettia) formation were markedly reduced, P restriction would be difficult to utilize for shoot length control in commercial crop production without compromising plant quality. However, the low P utilization efficiency at the higher levels of P fertilization indicated luxury consumption of P and suggested that for both crops, P fertilization could be markedly reduced compared to present recommendations without any negative effects on plant growth or development.

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Organic layers favor phosphorus storage and uptake by young beech trees (Fagus sylvatica L.) at nutrient poor ecosystems

Simon Hauenstein1, Harald Neidhardt1, Frederike Lang2, Jaane Krüger2, Diana Hofmann3, Thomas Pütz3, Yvonne Oelmann1

1University of Tübingen, Geoecology, Geosciences, Rümelinstr. 19-23, DE-72070 Tübingen, Germany

2 University of Freiburg, Faculty of Environment and Natural Resources, Soil Ecology, Bertoldstr. 17, 79098 Freiburg i.Br., Germany

3 Forschungszentrum Jülich - Institute for Bio- and Geosciences, IBG-3: Agrosphere, DE-52428 Jülich, Germany

Keywords: 33P; isotopic tracer; phosphorus nutrition; organic layer, nutrient poor ecosystem; nutrient uptake. The accumulation of organic layers in forests is linked to the ratio between litterfall

and decomposition rates, the latter being decelerated due to acidification and

associated with low nutrient availability. Nevertheless, the organic layers might still

represent an important interim storage and source pool for phosphorus (P) nutrition

of forests on P-deficient soils. We applied a mesocosm experiment with 3-year old

beach (Fagus sylvatica) saplings and soil from two forest sites characterized by

contrasting P status (nutrient-poor: LUE, nutrient-rich: BBR) in order to assess the

importance of the organic layers as a potential P source pool. We therefore

established two treatments, one that excluded the organic layers and one which

included it. 33P was added in form of orthophosphate to the mesocosms and the

trees were destructively harvested after 0h, 24h, 48h, 96h, and 192h, respectively,

after addition of the label. For each time step, the radioactivity was measured in

different soil P fractions and plant compartments (xylem, leaves, branches, stems)

along with total P concentrations. Measured P concentrations in respective soil

fractions and in foliar biomass were lower in LUE than in BBR (p ≤ 0.001). Accordingly,

soil and plant material was more intensely labeled in LUE as compared to BBR as

indicated by the specific 33P activities (ratio between radioactivity and stable isotope

P concentrations; 0.04 > p > 0.0001). More radioactivity was recovered in the

aboveground biomass in LUE than in BBR, which can be either attributed to a more

intense labelling effect in combination with a higher root density in the organic layers

in LUE. Less radioactivity was recovered in the NaOH-P fraction in LUE and BBR if the

organic layers were present, which was due to a combination of P retention and

increased plant uptake as well as different infiltrating regimes in presence of the

organic layers. The organic layers were crucial for the nutrient-poor site LUE as trees

were not able to maintain their productivity as indicated by decreased foliar- and

tree tissue P concentrations. Furthermore, P mobilization and efficient subsequent

uptake by aboveground biomass was significantly decreased. In conclusion, our

results highlight the importance of the organic layers for P nutrition of young beech

trees growing on nutrient poor soils.

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Optimisation of phosphate rick uptake to maize in the rhizosphere Nyamdavaa Mongol1, Jianbo Shen1, Philip M. Haygarth2

1Department Lancaster Environmental Centre, Lancaster University, Lancaster, LA1 4 YW, United Kingdom.

2Department of Plant Nutrition, China Agriculture University, Key Laboratory of Plant-Soil Interactions, Beijing 100193, PR China.

Keywords: Rhizosphere processes, P mobilisation, phosphate rock Rhizosphere processes provide a strong linkage between plant and soil and can increase phosphorus (P) mobilisation acidifying the soil in the root zone, dephosphorylation and chelating metal ions. Nowadays, low graded phosphate rock (PR) is also coming onto the market as a result of the depletion of high grade rocks. Direct application of this raw PR material involves a variety of factors and interactions to increase soil acidity and cation exchange capacity and avoid labour intensive and energy consuming manufacturing procedure. Therefore the aim of this study was to develop the rhizosphere approach to improve PR solubilisation processes in root medium and regulate plant P acquisition. This work tested the hypothesis that rhizosphere processes integrated acidification will have influence on P mobilization through root morphological and physiological properties under variable P conditionings including with soluble P, PR and combination of PR with a number of chemicals which can lower soil pH in root medium. A controlled pot experiment was used to establish Olsen P in soil and maize shoot P concentrations, root morphology and other rhizosphere parameters 50 days after planting. The results indicate that the rhizosphere processes and integrated acidification can improve P mobilisation and uptake, leading to increase plant growth. There is a strong positive relationship between plant biomass, plant P concentration and Olsen P, showing an upward trend as increase of P supply rate and involvement of acidification inducer. PR application in combination with sulfuric acid was most significant figure, whereas control and only PR were the lowest in terms of bioavailability. Use of PR could help with sustainable P use in the future.

Figure 1: Pot grown maize, day 48 after planting

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How does poultry manure and phosphate rock in agricultural soil affect soil P dynamics, plant biomass production and its stoichiometry?

Patricia Poblete-Grant1,2, María de la Luz Mora1, Cornelia Rumpel2 1 Center of Plant, Soil Interaction and Natural Resources Biotechnology, Scientific and

Biotechnological Bioresource Nucleus, Universidad de la Frontera, 54-D, Temuco, Chile 2Institute of Ecology and Environment of Paris (UMR), Campus AgroParis Tech, Thiverval-Grignon, France.

Keywords: Poultry manure, soil-plant stoichiometry Phosphorus (P) is one of the major limiting nutrients for plant growth in many agroecosystems, and continuous application of phosphate fertilizer is required to support agricultural production. Improved managements of P fertilizers may include recycling of organic waste materials. Poultry manure (PM) has a high P concentration. Due to simultaneous input of OM it may (1) increase SOC sequestration (Poblete-Grant et al., 2018) and (2) reduce the amount of phosphate rock needed when applied in combination. The aim of the study was to investigate the effect of PM and phosphate rock (RP) on biomass production, SOC storage and stoichiometry of the plant soil system of two agricultural soil types with contrasting pH. We carried out a 13C labeling experiment under laboratory conditions with ryegrass plant growing during seven weeks with four treatments: unamended soil, soil amended with PM (14 t ha-1, RP (0.84 t ha-1) and with a combination of both PMRP (9.8 t ha-1/0.5 t ha-1). We determined the elemental and 13C isotope content of plant biomass and soil. Additionally, soil P and SOC fractionation were performed. Our results showed that high pH soil only increased soil P in available fraction, while for the moderately acid soil also increased P contribution to the moderately available fraction was observed after PM and PMRP application. This led to higher biomass production in both soil types. RP increased only shoot biomass and most C was allocated to shoots. PM and PMRP increased significantly both, shoot and root biomass. The amount of C allocated to roots improved in these two treatments, thereby increasing SOC storage. However, in treatments with PM application we observed SOC losses, being higher for the alkaline soil as compared to the moderately acid one and influenced by the fertilisation. Higher SOC losses in the alkaline soil may be explained by an increased SOC mineralization to mobilise P from organic sources in this P deficient soil. The combination of PM and RP led to synergistic effects leading to similar losses as with PM alone despite lower application. We conclude that composted PM alone or in combination with RP may be suited to increase biomass production of grasslands with ryegrass plants. However, its impact on SOC sequestration need to be carefully assessed after accounting for greenhouse gas emissions. References - Poblete-Grant, P., Bobadilla, K., Condron, L., Rumpel, C., Demanet, R. and Mora, ML. (2018). Dynamics in soil phosphorus distribution in pastures growing on Andisols after several years of composted poultry manure application. Soil use and management (submitted).

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Effect of different sources of phosphorous on the production of a permanent grassland of Lolium perenne in an Andisol from Southern Chile

Rolando Demanet1, Ana Luengo Escobar1, Cecilia Paredes1, Marcela Calabi1, Patricia Poblete, Cornelia Rumpel2, María de la Luz Mora1

1Center of Plant, Soil Interaction and Natural Resources Biotechnology, Scientific and Biotechnological Bioresource Nucleus, Universidad de la Frontera, 54-D, Temuco, Chile

2UMR Université Paris, Campus AgroParisTech, Thiverval-Grignon, France.

Keywords: Cattle manure, Poultry manure, Andisol. One of the most important limiting factors in agricultural systems is the phosphorus (P) availability for plants. Phosphorus is a finite resource, so the use of farm wastes as P recycled sources is necessary for future sustainability of crops. A field experiment was carried out in two seasons (Nov 2016- Jan 2018) in an Andisol Barros Arana series with 10 mg kg-1 of P. Poultry manure (PM) and cattle manure (CM) were evaluated in combination or not with conventional sources of P, such as triple super phosphate (TSP) and phosphoric rock (PR) to a final maximal amount of 100 kg P ha-

1. Lolium perenne cv Nui plants were cultivated in parcels of 12 m2 and a basal fertilization of 46 kg N, 77.5 kg K2O, 22.5 kg S y 22.5 kg MgO ha-1. The chemical characterization of soil and pasture yield and nutrient quality was assessed. The most important results are showed in Figure 1. The highest PM treatment showed the highest P uptake and production of ryegrass during the first season. This performance was not sustained in the second season, where TSP treatment showed to be slightly higher. However, PM treatment remains to be the most significant (P ≤ 0.001) due to that during all the experiment accumulated around 15 ton ha-1 of ryegrass production, which represented 47% more than the control treatment (without fertilization) during the same period. Moreover, it is highlighted that the seasonal distribution showed that PM treatment was 35% higher than control in winter, but during summer, CM was 41% higher than control.

Figure 1: A. Monthly production distribution (ton ms ha-1) under different P sources. B. Total production (ton ms ha-1). Abbreviations: TSP: triple super phosphate, RP: rock phosphate, PM: poultry manure, CM: cattle manure. One-way ANOVA was used to evaluate differences between P sources. * = P ≤ 0.001

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Optimizing ryegrass P acquisition and productivity by using manure labile P in contrasting Andisol soils under different Ca and N fertilization

Ana Luengo Escobar1, Cecilia Paredes1, Rayen Millaleo1, Paola Duran1, Patricio Barra1, Milko Jorquera1, María de la Luz Mora1

1Center of Plant, Soil Interaction and Natural Resources Biotechnology, Scientific and Biotechnological Bioresource Nucleus, Universidad de la Frontera, 54-D, Temuco, Chile.

Keywords: Andisol, ryegrass, cattle manure. Recycle P from farming wastes as cattle manure (M), an enriched labile P bio-fertilizer, is a great prospect to improve P availability for plants. However, the interaction of this bio-fertilizer with Urea as Nitrogen (N) source and Lime (L), a common Calcium (Ca) amendment in soils from Southern Chile, is not well understood. In this study we proposed to evaluate the behavior of different P sources under different levels of N and L amendments and their interaction in different Andisol soils types, Barros Arana (BA) and Toltén (T) series. Both soil have contrasting P and Al content (Fig. 1A). The capacity of different P sources such as Triple super phosphate (TSP) and M, and the use of a Bacterial consortia to ameliorate Al and optimize P acquisition in ryegrass (Lolium perenne) plants in a controlled rhizobox experiment was conducted. At the end of experiment (90 days), roots and shoots were sampled and different chemical and biochemical parameters (P, Ca, Al, pH, malondialdehyde content, SOD, POX and Pasa activity), were evaluated to assess the plant performance.

Figure 1: A) Barros Arana and Toltén soils, contrasting in P and Al saturation. B) Best treatments are presented per each soil. 150 and 300 kg ha-1 Nitrogen as Urea, no Lime (-Lime), 1600 kg ha-1 Lime (+L), and Cattle Manure (0.62% of P) (M). B). Ryegrass DW and P concentration in shoots. Significant differences between TSP and M are presented. * P ≤ 0.001. Manure treatment showed the highest results in productivity in both soils, but in the BA soil, +L amendment was necessary, meanwhile in T soil, - L showed the highest values (Fig. 1B, C). About N, the lowest level showed the best results in both soils.

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Additionally, a principal component analysis revealed different groups of responses among treatments and soil types. Plants in T soil that showed a better production, exhibited higher levels of P on the leaves, higher available P and higher pH both in the rhizosphere. However, for BA soil, the best results can be associated to the increment of the root biomass. It is highlighted that even do the low P and high Al content of BA soil, the use of M improved the productivity of ryegrass compared those levels reached by T soil.

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Polyphosphate fertilizer hydrolysis characteristic and its effects on soil P availability

Xuewei Wang1,2, Yanju Gao1, Guixin Chu1,2, Baowei Hu2

1Department of Resources and Environmental Science, College of Agriculture/ The Key Laboratory of Oasis Eco-agriculture of the Xinjiang Production and Construction Corps, Shihezi

University, Shihezi, 832003, P. R. China. 2College of life science, Shaoxing University, Zhejiang, 312000, P R China.

Keywords: polyphosphate hydrolysis, P transformation, PUE. Polyphosphate is an alternative P sources substituting ortho-phosphate based P fertilizers. Understanding the characteristics of hydrolysis rate of polyphosphate significantly affect the transformation of phosphorus in soil and its fertilizer efficiency are the prerequisite for reasonable polyphosphate fertilizer application. In this study, aqueous and soil incubation experiments were conducted to test the effects of pH and temperature on polyphosphate hydrolysis in aqueous and soils. And a pot experiment was also conducted to explore the influences of polyphosphate fertilizers and MAP on soil available-P, inorganic P transformation in soils in both calcareous and acidic red soils were also investigated. The experiments included four polyphosphate fertilizers (solid and liquid ammonium polyphosphate, polyphosphoric acid and mono ammonium phosphates) and two soil types (acidic and alkaline). Incubation experiments showed that in aqueous condition, the averaged amount of PO43- released from polyphosphate fertilizers at 35°C condition was 2.7 times greater than at 25°C. The averaged Olsen-P in polyphosphate-treated soils at 35°C was 1.12 times greater than at 25°C. Polyphosphate hydrolysis increased with pH decreasing in aqueous solution, but its hydrolysis rate was greater in calcareous soil than in acid soil. Pot experiment showed that compared with MAP, polyphosphate fertilizers significantly increased soil available P concentrations in calcareous soil. Soil water soluble-P and Olsen-P were increased by 19.3 and 25.4%, respectively, and soil resin-P and NaHCO3-P and NaOH-P increased by 22.8, 43.3 and 33.8%, respectively. These imply that polyphosphate can significantly reduce the fixation of P and significantly increased rape dry weight and PUE in calcareous soil, but those were not truth in acid soil. In summary, polyphosphate hydrolysis increased as temperatures increased. Low pH favored polyphosphate hydrolysis in the aqueous incubation, whereas the opposite was true in the soil incubation.The difference may be attributed to differences in soil texture and cation concentrations. Polyphosphate fertilizer can overcome some inherent drawbacks of orthophosphate-based P fertilizers regarding its effect on increasing soil P availability, plant P nutrition and PUE, especially in calcareous soil.

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Figure 1. Graphic abstract of incubation experiment (A) and pot experiment (B)

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Does addition of humic acid enhance the effectiveness of phosphate fertilizers? Rodrigo C. da Silva, Fien Degryse, Roslyn Baird, Michael J. McLaughlin

Fertilizer Technology Research Centre, School of Agriculture, Food & Wine, University of Adelaide, Waite Campus PMB1, Glen Osmond SA 5064, Australia.

Keywords: Phosphate fertilizers, humic acid, enhanced-efficiency fertilizers Humates (humic or fulvic acid) are increasingly used in mineral fertilizers. Claims have been made that the addition of humates to P fertilizers may reduce P "fixation" in soil and enhance P availability to plants. In this study, we tested three humate-amended fertilizers in incubation and pot trials. Two fertilizers were commercial fluid fertilizers: (i) a liquid ammonium phosphate (7-21-0) with 7% humic acids derived from leonardite and (ii) a phosphoric acid (0-50-0) with 6% humic substances. These products were compared against phosphoric acid (0-52-0) and fluid or granular monoammonium phosphate (MAP, 11-52-0). The third product was a granular complexed single super phosphate (CSSP) which was compared with SSP. The (C)SSP samples were made from phosphate rock and sulfuric acid, with or without addition of Aldrich humic acid, according to Erro et al (2013). The products were compared by assessing the diffusion in a Petri dish incubation (up to 44 d) using the visualization method of Degryse & McLaughlin (2013), and by assessing the P availability to wheat in a pot trial using an acid and alkaline soil. The P diffusion visualization showed no advantage from the use of humate-amended fertilizers in either soil. There were also no significant differences in yield or P uptake between the P treatments in the pot trial (example in Fig. 1). In conclusion, we did not find any evidence that addition of humic substances to phosphate fertilizers enhances their effectiveness. Figure 1: Dry matter yield of wheat grown in and acid soil at 100 mg P/kg (added as granular of fluid MAP, phosphoric acid, or fluid humate-amended fertilizer) or without P (Ctr). Pictures above the bar show the visualized P diffusion zone around the fertilizer (applied at 9 mg P) in the same soil after 1 day. References - Degryse F, McLaughlin MJ (2014). Phosphorus diffusion from fertilizer: visualization,

chemical measurements, and modeling. Soil Sci Soc Amer J 78:832-842. - Erro J, Baigorri R, Garcia-Mina J, Yvin JC (2013) Phosphate compounds and use thereof as

fertilizer. US Patent 20130104612

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Mobilization of phosphorus from phosphate rock: can phosphate rock be a source of phosphorus for plants?

Abdelwahed Hamdi1, Ons Talbi1, Hans Werner Koyro2, Chedly Abdelly1 1Laboratoire des plantes extremophiles, Centre de Biotechnologie de Borj Cedria,

2 Institute of Plant Ecology, University of Giessen, Germany Keywords: Phosphate rock, availabity, mobilization, biologicals tools, compost, biochar. One of the options to remove soil fertility constraints for sustainable agriculture is to develop soil nutrient management based on the technologies of adequate supply and feasible input of organic and inorganic fertilizers. In modern agriculture intensive use of phosphate fertilizers poses many environmental problems. The direct use of natural phosphates seems to be an alternative to polluting chemical fertilizers. However, the use of this natural product remains limited given it low solubility in soils. The development of biological tools to increase the availability of natural phosphates is a very efficient tool. The contribution of organic residues such as compost biochar, inoculation by fungi and bacteria presents the most method used for the phosphorus mobilization. Seedlings of sulla carnosa previously germinated on perlite were grown in green house condition under different experimental conditions (0P, Compost (0.75%), Biochar (0.75%), Phosphate rock (50ppm / kg), PR + Compost, PR + Biochar and combination PR + Compost + Biochar). The analyzes focused on the physiological behavior of plants: Biomass production, photosynthetic gas exchange, chlorophyll fluorescence, chlorophyll and the anti-oxidation system. Results shows that compost addition improve the growth of sulla carnosa, opposed to biochar the application of biochar alone or combined to compost seems to have a negative effect this is proved by the result of Biomass production as well as the photosynthetic gas exchange which suggests that the application of compost can induce an increase of the availability of Phosphorus and other element. while biochar Bind phosphate, which is probably the origin of the negative effect observed. The result of this physiological investigation shows that adding compost as an additive to increase phosphorus availability from natural phosphates could be a promising tool.

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Respective roles of Fe-oxyhydroxide dissolution, pH changes and sediment inputs in dissolved phosphorus release upon reduction of wetland soils

Sen Gu1, Gérard Gruau1, Rémi Dupas2, Patrice Petitjean1, Qingman Li3, Gilles Pinay1 1Univ Rennes, CNRS, OSUR, Géosciences Rennes - UMR 6118, F-35000 Rennes, France.

2INRA, UMR 1069, SAS, Agrocampus Ouest, 35000, Rennes, France. 3Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072, China.

Keywords: Dissolved phosphorus, riparian wetland

The development of anoxic conditions in riparian wetland (RW) soils has been widely recognized to release dissolved (<0.45µm) phosphorus (P), but the respective roles of soil P speciation, soil Fe oxyhydroxide reductive dissolution, pH changes during reduction reactions and sediment inputs on this release remain a controversial issue. In this study, we attempted to unravel and quantify these different roles by performing laboratory anaerobic/aerobic incubations on RW soils with and without sediment addition. The selected soils are two RW soils with contrasting soil P status and organic matter (OM) content, coming from a small agricultural watershed in western France. The added sediments come from the agricultural field immediately above the RW. Soil solutions from all incubations were analyzed for dissolved molybdate-reactive P (MRP), dissolved total P (TP), dissolved organic carbon (DOC), nitrate, sulfate, and Fe(II) concentrations. We found that the concentrations of TP and MRP released correlated positively with the total P and extractable P contents, but negatively with the OM contents of corresponding soils. The Fe:P molar ratios of anaerobic soil solutions were lower (<1.4) in soils with high oxalate extractable P (P-Oxalate) and low oxalate extractable Fe (Fe-Oxalate) than in soils (up to 12.0) with low P-Oxalate and high Fe-Oxalate. The dissolved P (DP) release was mainly controlled by the Fe-oxyhydroxides reductive dissolution mechanism (83%) in the soils with high extractable P and low OM contents, whereas that released in soils with low extractable P but high OM contents was mainly controlled by the pH change mechanism (88%). Moreover, the mixture of eroded soil sediments with RW soils enhanced the release of DP, DOC and Fe(II) by 16, 4 and 18%, respectively, as compared to reduction of the sediment and RW soils separately. The results of the present study suggest that soil properties controlled the concentration and speciation of DP released under anoxic conditions and also their potential transfer risk. The clear difference in the controlling mechanisms of DP release between soils implies that management options to reduce DP transfer from RW soils should be designed with reference to soil properties. Management efforts should try to limit the soil erosion from upland fields to avoid the deposition of P-rich sediments into

RW soils. Figure 1: Dissolved phosphorus release under anoxic conditions in riparian wetland

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Long-term field observations reveal phosphate leaching in sandy agricultural soils

Annemieke van der Wal1, Patrick van Beelen1, Eke Buis1 1National Institute for Public Health and the Environment, Antonie van Leeuwenhoeklaan 9,

3721 MA, Bilthoven, The Netherlands. Keywords: Phosphate, leaching, agriculture

The soil phosphorus (P) surplus of agricultural fields mainly accumulates via the application of manure and mineral fertilizers. Long-term application of repeated fertilization contributes to soil P saturation, which can eventually lead to loss of P to drainage water and groundwater. P is the major nutrient promoting algae and aquatic weed growth, thereby negatively affecting freshwater biodiversity and quality of drinking water. P in the form of phosphate can precipitate with calcium ions in alkaline soils. In acid soils phosphate can bind to dissolved iron or aluminium and becomes unavailable to plants. There is, however, a limit in the capacity of soils to retain P. In this study we investigated if phosphate leaching occurs in Dutch agricultural sandy soils using a national long-term monitoring network. Each year in summer since 1992 per farm 16 drill holes were made to sample the upper meter of groundwater. On average about 35 to 200 farms per year per farm type were sampled. In the laboratory 2 mixed samples were made per farm and analyzed for among others phosphate concentrations. The phosphate concentration in the water that leaches from the root zone in sand seems to slowly increase since 2008 (Fig. 1). This is especially the case on dairy farms. In our presentation we will zoom in on individual farms that have been sampled for many (>10) years. The number of significant regression coefficients (relationship between phosphate concentration and time) shows that an increase in phosphate leaching is common over almost all sampled farms. Our results show that on farms with sandy soils, phosphate seems on average to be leaching from the root zone. In this study we will assess if this increase is caused by leaching due to P saturated soils, or that other factors are causing this phenomenon. We will discuss these results in relation to other soil aspects relevant for P leaching. Figure 1: Phosphate concentrations since 1992 in the upper groundwater at two different farm types.

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Trends in P concentration of tree foliage across Germany Inken Krüger1, Andreas Schmitz1, Daniel Ziche1, Tanja Sanders1

1Intensive Forest Monitoring, Thünen Institute of Forest Ecosystems, Alfred-Möller-Str. 1, 16225 Eberswalde, Germany.

Keywords: ICP Forests, foliar nutrient concentrations, tree nutrition Foliar phosphorus (P) and nitrogen (N) concentrations serve as indicators for the nutritional state of forest trees and their productive capacities. Atmospheric deposition affects nutrient availability and can cause nutrient imbalances in forest ecosystems. In Germany, this is measured on intensive monitoring sites of the Federal States and the ICP Forests programme (International Co-operative Programme on Assessment and Monitoring of Air Pollution Effects on Forests). Biannual measurements of the chemical composition of leaves and needles allow the identification of nutrient limitations and surpluses depending on tree species (European beech (Fagus sylvatica), Norway spruce (Picea abies), Oak (Quercus petraea x robur), and Scots pine (Pinus sylvestris)). Further data on atmospheric deposition, meteorology, and pedology is analyzed to identify the driving factors behind spatial and temporal patterns in foliar phosphorus concentrations. P deficiency defined by critical foliar concentrations published in the literature is found for 52 % of spruce, 44 % of oak, 40 % of beech, and 9 % of pine samples. Disharmonious N/P nutrition almost exclusively occurs as wide N/P ratios. Of the investigated tree species, beech shows the highest percentage of samples above the critical ratios (47 %). Within the period 1995 to 2015, foliar P concentration significantly decreased in beech (-4.9%) and pine (-2.9%), but remained unchanged in spruce and oak. The driving factors behind these temporal patterns for each tree species will be presented at the symposium.

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HABNORM - Environmental quality standards for European protected habitat types and habitats of species: phosphorus in soil and water

Cécile Herr1 1Research Institute for Nature and Forest, Herman Teirlinckgebouw, Havenlaan 88 bus 73, 1000

Brussels, Belgium.

Keywords: Natura 2000 habitat, conservation status The Habitats Directive requires European protected habitat types and habitats of species to be brought to and maintained in a favourable conservation status. Knowledge of the environmental requirements of these habitat types and habitats is essential in order to meet this condition. In particular the availability of phosphorus in soil and water has been shown to be of paramount importance for the conservation of oligotrophic habitats. In this project (running from 2015 to 2020), a thorough abiotic and biotic characterization of the European protected habitat types and habitats of species occurring in Flanders, Belgium, is being performed. The objective is to develop a concept to quantify ranges for environmental variables needed to obtain a favourable conservation status. We visited reference sites hosting typical and degraded forms of the habitats in equilibrium with the environment and collected information about the plant species composition and the characteristics of the soil, groundwater and surface water. This included the orthophosphate and total phosphorus concentrations in water, and the total and bioavailable phosphorus concentrations in soil. The local conservation status of the habitat was determined for each location. On the basis of this quantitative information, a favorable abiotic range can be derived for each habitat (sub) type. This is the global reach of an environmental variable within which a habitat type can function sustainably. These results will lead to quality standards/benchmarks which can then be included in a legislative framework. A better knowledge of the abiotic requirements of a habitat is also important to assess environmental problems and possibilities of restoration.

Figure 1: A range (10-90 percentiles) for soil phosphorus

considering all plots with respectively unfavourable and

favourable conservation status for Northern Atlantic wet

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Feedbacks between treeline shift and nutrient availability in Northern Russian mountains

Jasmin Fetzer12, Pavel Moiseev3, Frank Hagedorn1

1 Forest Soils and Biogeochemistry, Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Zürcherstrasse 111, 8903 Birmensdorf, Switzerland

2 ETH Zurich, Department of Environmental Systems Science, Universitätsstrasse 16, 8092 Zürich, Switzerland

Keywords: Treeline shift, nutrient availability, climate warming Treelines are distinct vegetation boundaries from tundra to forests which have shifted upward during the last decades in various mountain regions around the globe. These shifts have mainly be attributed to climate warming. In our study, we examined the influence of nutrient availability on treeline shifts. We hypothesized that a more favorable microclimate in the forest enhances nutrient mineralization which fosters the forest expansion. In remote areas of the Ural and Khibiny mountains of Northern Russia, we have sampled plants and soils along six elevational transects reaching from the tundra to subalpine forests, representing treeline shifts in a space for time approach.

Figure 3. (A) Ammonia stock per height level for Tree and Open samples; (B) Resin extractable P from the Open and Tree plots; (C) Microbial phosphorus as mean of Tree and (black); (D) Phosphatase activity for Open and Tree plots.

Results show that available nitrogen (N) and phosphorus (P) in the soil increases with decreasing elevation, i.e. from the tundra to the subalpine forest. Concentration of N and P in needles showed the same pattern. The increase in soil and plant nutrients was most pronounced from the tundra to the species line, while plant nutrient contents even decreased from the species line towards the subalpine forest. We interpret that these findings indicate a positive feedback between treeline advance and nutrient availability, very likely due to an accelerated organic matter turnover under the more favorable microclimatic conditions under tree canopies. However, with ongoing forest development nutrient cycling is becoming increasingly tighter due to the binding of nutrients in biomass.

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Effect of mineral fertilizers application on selective soil chemical properties Abdalhakim M.A. Ksheem1 and Alaa Tekbali1

1Soil and water department, Faculty of Agriculture, University of Tripoli, P.O.Box 13467 Libya.

Keywords: Available soil P, calcareous soil, urea-phosphate. The effect of applying fertilizers on soil fertility and plant nutrition was well documented (Haynes&Naidu, 1998; Warman, 1986), but their effect on soil chemical properties are still under agreements. This study hypotheses that applying acidy phosphoric fertilizers in calcareous soil may improve soil chemical properties, thus, this study was aimed to evaluate the effects of applying urea-phosphate on soil chemical properties. The pots trial was conducted in fall 2016, in Research Station Faculty of Agriculture, University of Tripoli. The 24 pots were filled out by 7 kg air dry soil and four levels of phosphorus (P) were applied (0, 150, 200 and 300 ppm (mg kg-1) by using two different phosphorus fertilizers named as di-ammonium phosphate (DAP) and Urea-phosphate (UP). One lettuce plant was planted in each pot. A distilled water at filed capacity percentage was added to all pots to make up uniform soil moisture level in all pots. The soil samples were taken during experiment after 1, 2, 3, 4 weeks to measure; soil chemical properties. The data reported correspond to the mean value of three replicated measurements (n=3). Statistical analyses were undertaken using the statistical package SPSS V13 (Cramer, 2004). Application of urea phosphate at the rate 300 mg P2O5/kg significantly reduced soil pH after one week comparing to other treatments. However, after 2nd, 3rd and 4th weeks, the soil pH was decrease to 6.4 with applying 300 mg P/Kg as UP comparing to soil pH of control 7.5. On the other hand, the soil EC was found not affected by type of fertilizer, while the rate of application affected the soil EC after week 4th. Both fertilizer type and rate of application were found to have significant effect on available soil P. The available soil P increased in soil with increase of rate of application of urea –phosphate. Finally, it was found that the available soil P has negative relationship with increase of soil pH (R = -0.67). In conclusion, applying urea phosphate could lead to decreased soil pH and increase available soil phosphorus.

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Interactive effects of nitrogen and phosphorous addition on plant growth

Ying-Ping Wang1, Jun Jiang2 and Junhua Yan1

1 CSIRO Oceans and Atmosphere, Aspendale, Victoria 3195 Australia 2Terrestrial Biogeochemistry Group, South China Botanic Garden, Guangzhou, 510650 China

Keywords: Nutrient limitation, interaction

Productivity of terrestrial ecosystems is often limited by nitrogen, phosphorous, or co-limited by both (Harpole et al. 2011). The degree of co-limitation for a given ecosystem strongly depends on the directions of interactions (additive, synergistic or antagonistic) between nitrogen and phosphorus, and the amount of nutrients added. Two recent meta-analyses of field observations drew quite different conclusions about the consequences of N and P interaction in the tropical forest: aggravating P limitation with N addition through diluting leaf P concentration (Li et al. 2016), and accelerating P cycling with N addition by increasing biochemical P mineralization (Deng et al. 2017). In this study, we compiled observations of ecosystem responses to N and P additions from 133 studies with full factorial experimental treatments (control, +N only, +P only, +NP). Our results show that addition of N or P increases the accumulation of added nutrient in leaf and aboveground biomass. Interaction of N and P is synergistic on aboveground biomass or aboveground NPP across all four different ecosystem types, but is variable for other processes among different ecosystems types. For subtropical or tropical forests, interactive effect is synergistic for leaf P, but antagonistic for available soil P; interaction is synergistic for leaf N: P ratio, but antagonistic for leaf N in grasslands and leaf P for tundra. In the P-limited wetlands, interactive effect is synergistic for leaf N: P ratio and available soil P, but antagonistic for root P. Therefore the processes underlying the synergistic responses to N and P addition vary among different ecosystem types. Our result does not support the antagonistic interaction of N and P additions on nitrogen cycling in tropical forests. References - Deng Q, Hui DF, Dennis S, Reddy KC (2017) Responses of terrestrial ecosystem phosphorus cycling to nitrogen addition: A Meta-analysis. Global Ecology and Biogeography - Harpole WS, Ngai JT, Cleland EE, Seabloom EW, et al. (2011) Nutrient co-limitation of primary producer communities. Ecology Letters, 14:852-862. - Li Y, Niu SL, Yu GR (2016) aggravated phosphorus limitation on biomass production under increasing nitrogen loading: a meta-analysis. Global Change Biology, 22:934-943

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Evaluation of the New York phosphorus index using a 33,000-field database

Mart B.H. Ros, Quirine M. Ketterings, Sebastian Cela, Karl J. Czymmek Nutrient Management Spear Program, Department of Animal Science, Cornell University, 326

Morrison Hall, Ithaca, NY 14853, United States of America.

Keywords: phosphorus index; P transport; BMP Phosphorus (P) loss from agricultural fields can result in degradation of water quality, potentially contributing to surges of harmful algal blooms. Across US, the P index (PI) is the main method to improve P management of farms and minimize P losses to the environment. The PI is a management tool that identifies areas with high risk of P transport and helps plan application of P fertilizers and animal manure. Due to limited water quality improvement in prominent watersheds across the US, states have been required to revise, implement, and validate their PI (USDA-NRCS 2011). For New York (NY), the current PI (Czymmek et al. 2003) ranks farm fields based on P sources (fertilizer P, manure P, and soil P), combined with field characteristics that indicate transport risk (e.g. erosion rate, distance to a stream) following a source × transport approach. Recently, a new approach has been proposed, which first ranks fields based on landscape-driven transport factors, and then aims to incentivize the use of best management practices (BMPs; such as manure injection rather than surface application) to reduce the risk of P transport from high-risk fields (Ketterings et al. 2017). This new landscape × BMP approach was developed with stakeholder feedback to identify landscape factors and BMPs that are important for management decisions at the farm level. With edge-of-field water quality data lacking, the next steps in the evaluation of the new PI are (1) the use of P loss simulation models, and (2) whole-farm and statewide assessment of the impact of implementing a new PI on manure management options for farm fields. A unique database of 33,327 agricultural fields in NY was assembled in collaboration with nutrient management planners and farmers. Our analysis of the database indicates that, under the current PI, 1.7% of the fields are cut off from P application, and 3.0% are limited to crop P removal-equivalent application rates. The current PI allows application on high-risk fields as long as soil test P is low. A scenario evaluation shows that the proposed landscape x BMP approach limits P application on fields with a high transport risk, while simultaneously incentivizing the adoption of BMPs in such high-risk areas. This study illustrates the pivotal role of involving stakeholders in the assessment of nutrient management tools, as well as the importance of an incentive-driven approach for maintaining and improving water quality in the future. References - Czymmek KJ, Ketterings QM, Goehring LD, Albrecht GL (2003) The New York phosphorus

runoff index- User’s manual and documentation. CSS Extension Publication E03-13. 64 pp http://nmsp.cals.cornell.edu/publications/extension/PI_User_Manual.pdf

- Ketterings QM, Cela S, Collick AS, Crittenden SJ, Czymmek KJ (2017) Restructuring the P index to better address P management in New York. J Environ Qual 46:1372-1379. doi:10.2134/jeq2016.05.0185

- USDA-NCRS (2011) Title 190: National instruction. USDA-NRCS. Washington, DC. https://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/stelprdb1046179.pdf

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Effects of soil organic matter on particulate P transport in soils: a leaching column study

Mieke Verbeeck1, Erik Smolders 1 1Division of Soil and Water Management, KU Leuven, Kasteelpark Arenberg 20, 3001 Heverlee,

Belgium.

Keywords: Colloid-mediated P transport in soils, competitive sorption Phosphorus (P) is known to be responsible for eutrophication of water bodies as a result of high fertilization on agricultural soils. In soil and water systems, P is mainly present as phosphate, which has a strong affinity for sorption onto iron (Fe), aluminium (Al) and manganese (Mn) hydroxides. Soil organic matter can alter P mobility in soils, due to sorption of humic substances onto metal hydroxides, resulting in reduced P sorption capacity. In this study, the effect of soil organic matter was studied on particulate P transport in leaching soil columns. The hypotheses are that i) humic substances can increase mobilization of soil colloids due to colloid stabilization by steric and electrostatic hindering and ii) humic and fulvic acids can alter the P bearing capacity of mobilized soil colloids due to competition for sorption sites. Leaching columns were prepared with moist and homogenized surface and subsoil samples and i) leached with artificial rainwater under unsaturated conditions at two different Darcy fluxes; ii) after initial leaching with artificial rainwater, a dry period was imposed and iii) after initial leaching with artificial rainwater, the columns were waterlogged. Leachates were analyzed for total and “free” (i.e. <10kDa) P, Fe, Al, Mn, calcium (Ca) and dissolved organic carbon (DOC). Total P concentration in the topsoil leachates were ~150 µg/l P for all treatments, however, in the subsoil leachates, total P concentrations increased strongly in all treatments, i.e. from below detection limit (30 µg/l P) up to ~400 µg/l P. Total P concentrations were strongly positively correlated with total Fe, Al and Mn concentrations (up to ~50 mg/l Fe/Al and ~1 mg/l Mn). Particulate P concentrations of ~100 µg/l P were correlated with particulate Fe concentrations of ~10 mg/l Fe, i.e. Fe/P (M/M) ratio of ~50, while the particulate Fe concentrations were most strongly negatively correlated with free Ca concentrations. Our results show that colloid-mediated transport of P can increase P mobility in soils, but only when soil water Ca concentrations are low (<10 mg/l Ca), due to electrostatic repulsion of soil colloids at low ionic strength. Further results on total and particulate P leaching in soils with different organic matter concentration will be presented at the conference.

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Developing and delivering site-specific fertilizer recommendations

through an “agronomy at scale” approach: the case of predicting P

response in cassava and maize Pieter Pypers*1, Meklit Chernet1, Guillaume Ezui2 and Bernard Vanlauwe1

1International Institute of Tropical Agriculture, Nairobi, Kenya

2International Plant Nutrition Institute, Nairobi, Kenya

Much of the conventional agronomy research to develop fertilizer recommendations

has been conducted through researcher-managed field testing, typically involving

relatively small numbers of field locations deliberately chosen to represent

contrasting agro-ecological conditions. Especially under smallholder conditions in

sub-Saharan Africa, this has only been moderately successful, as it revealed the

impact of local soil and management conditions on the effectiveness of fertilizer,

including P fertilizers. The requirement to tailor interventions to the biophysical and

socio-economic conditions of smallholders has hampered the development of fitting

recommendations needed to intensify production systems at regional scale, and in

turn, large-scale development impacts to enhance food security.

We applied the “Agronomy as Scale” principles and approaches to develop a decision

support tool that provides site-specific fertilizer recommendations to smallholder

farmers. This involves GIS-assisted sampling frames for nutrient omission field trials

and observational studies, capturing the influence of covariates at various scales to

maximize the prediction accuracy when extrapolating findings across a target

intervention area. Data are collected using innovative methods, including barcoding,

Open Data Kit software and smart devices to ensure all data are geo-referenced,

reliable and available in near-real time at reduced financial and labour costs. Data

then feeds into a semi-automated statistical analysis system, and the output is used

in a coupled and spatialized LINTUL and QUEFTS model. These models use data from

various open-source soil and weather databases to estimate the water- and nutrient-

limited crop yields, and predict fertilizer response across the target intervention

area. In the decision support tool, an economic module is added to optimize for net

revenue within a given investment capacity supplied by the user.

Cross-validation results from 3 years of field research and over 1,000 fertilizer

response trials show that such an approach can deliver recommendations which

outperform standard blanket recommendations. This can be attributed to the ability

of the model to account for limitations in crop growth due to rainfall, in combination

with the effects of soil properties on crop response. Soil properties

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ORAL PRESENTATIONS Thursday 13 September

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Response to Phosphorus: A Key Driver to Variability in Yield to

Fertilizer Application in Smallholder Farms of Africa

Samuel Njoroge1, 2, Antonius G.T.Schut1, Ken E. Giller1, Shamie Zingore2 1Plant Production Systems, Wageningen University, P.O. Box 430, 6700AK, Wageningen, The

Netherlands 2International Plant Nutrition Institute, ICIPE Compound, Box 30772, Nairobi, Kenya

Keywords: Yield variability, Response to P

Current fertilizer recommendations in majority of smallholder farming systems in

sub-Saharan Africa (SSA) assume similar yield response to fertilizer application across

all fields in a region. However, application of fertilizers in these farming systems is

characterized by large variations in yield responses, and poor returns to investments

which discourage fertilizer use among smallholder farmers. The objectives of this

study were to: (i) assess the magnitude and spatial-temporal patterns of maize yield

response to N, P and K application; (ii) identify and characterize clusters of farms

with similar yield response patterns to N, P and K; (iii) identify the key drivers of

variability in maize yield response to applied N, P and K. Multi seasonal on-farm

nutrient omission trials were used to assess maize yield responses to N, P and K

application. Nutrient omission trials were conducted on 23 farms located in Sidindi,

Western Kenya, selected to be representative of the main soil and management

factors in maize based systems in Siaya County. Treatments included a control and

PK, NK, NP and NPK applications applied every season to the same plots. The trials

ran for seven consecutive cropping seasons from 2013 to 2016, while treatments and

location of the plots did not change. Large differences in maize yield responses to N,

P and K applications were observed with yield ranges of 1.3 – 5.7, 2.4 – 9.3, 2.0 – 7.6

and 2.2 – 8.5 t ha-1 for the PK, NK, NP and NPK treatments respectively in the first

cropping season. Six main maize yield response categories were identified that

differed in the maize grain yield responses to recursive N, P and K applications.

Identified yield response categories mainly differed in yield response to phosphorus

(P) over space and time. Accounting for past manure use significantly reduced the

variation associated with response to P. Average yield in the NK treatment for fields

without past manure use was 2.5 t ha-1, while for fields with past manure use,

average yield was for the same treatment was 5.2 t ha-1. We conclude that the strong

spatial-temporal patterns observed are mainly driven by variation in yield response

to P between farms. This is mainly as a result of previous farm management effects

including the use of livestock manure on soil P stocks. Accounting for the different

sources of P within smallholder farms can assist in developing improved fertilizer use

recommendations, resulting in increased fertilizer use efficiency.

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Liming as a prerequisite for improving food security in Ethiopia

Kari Ylivainio, Refissa Leta, Tilahun Geleto, Minna Sarvi, Martti Esala, Tegist Chernet

Natural Resources Institute Finland (Luke), Tietotie 4, 31600 Jokioinen, Finland

Keywords: Liming, soil acidity, fertilization

We studied potential of liming in improving phosphorus (P) utilization and consequent effects on wheat yield and its quality in acidic soils of Ethiopia. Agricultural productivity is a major challenge when considering food security in sub-Saharan Africa. One of the main restrictions for increasing soil productivity is large areas of acidic soils. Especially P deficiency is a major restriction for food production in weathered soils. In this study we evaluated the effects of liming and P fertilisation on wheat yield, its quality and nutrient utilization in highly P deficient acidic soils in Ethiopia. Two field trials were established around Nekemte, located in Ethiopian highlands. Dolomitic lime was applied at 0, 6 and 12 t ha-1 rates (Fig. 1) for 47 days prior to sowing of wheat (var. Danda'a, 84 kg ha-1) in early July 2014. Each lime treatment included P application rates of 0, 11, 32, 63 and 95 kg ha-1 as DAP. Nitrogen was given as urea (108 kg ha-1) during planting and complemented one month after planting (30 kg ha-1). During growing season weeds were controlled by hand and by using 2,4-D. Harvesting was conducted end of November (Fig. 1) by hand threshing. Yields were calculated to 15% moisture content. Elemental concentrations in grains were analyzed in Finland.

Figure 1: Plowing

experimental fields after lime application (left) and experimental field before harvesting (right).

Depending on field conditions, liming increased wheat yield, its quality and P utilization efficiency drastically. For optimum yield, taken as 90% of the maximum, P requirement was decreased down to 20 kg ha-1 with the highest lime application rate. Together with liming, P application increased grain nutritional value by increasing essential element concentrations. Soil acidity is a major factor depressing crop production in Ethiopia that cannot be compensated with fertilisers. On the contrary, liming decreased P requirements, optimum yield being reached with moderate P application rate even in extremely P deficient conditions. Uptake of micronutrients was not depressed by liming and P application further increased their content in grains. Improving food security in Ethiopia requires better management of acidic soils and the first step is to determine adequate lime and fertiliser application rates for depressing malnutrition.

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Increasing the sustainability of phosphorus use by root/rhizosphere

management in cropping systems of China

Jianbo Shen, Xiaoqiang Jiao, Yang Lyu, Haigang Li and Fusuo Zhang

Center for Resources, Environment and Food Security, China Agricultural University, Beijing

100193, China

Keywords: Sustainable phosphorus use, rhizosphere engineering, root-zone management

Applying chemical phosphorus (P) fertilizers to cropping system makes a substantial

contribution to increasing grain production in Chinese agriculture, representing one

of the most effective technical approaches in Green Revolution. China has

historically experienced three phases in P use, including P resource shortage,

gradually increasing P input, and overuse of P fertilizers. The challenges facing

agriculture today are even much greater for achieving high P use efficiency and high

crop productivity together while increasing environmental resilience over the next

decades. However, over the last 30 years crop yield has not increased

proportionately with increasing P fertilizer inputs, leading to low P use efficiency and

increasing environmental risk such as eutrophication and P runoff or leaching loss.

Using a combination of national and regional survey and long-term and/or multiple-

site field experimental data covering the major crops (maize, wheat, and rice) in

China, we charted the dramatic rise in legacy soil P, and the corresponding decline

in fertilizer P recovery efficiency. Traditional nutrient management is highly

dependent on the external fertilizer inputs but overlooks exploiting the biological

potential through stress management, involving modified crop biology, root-zone

management and rhizosphere manipulation for efficient P use (Shen et al., 2013).

Compared with developed countries, excessive P fertilizer use in major Chinese

croplands causes significant decline in P use efficiency, resulting in increasing

resource and environmental costs. To address the challenges, a “high yield, high

nutrient use efficiency - double high” technology system has been developed

through increasing grain yield by crop management to realize yield potential,

increasing P-use efficiency by root-zone or rhizosphere management to maximize

biological efficiency. We show that P recovery efficiency in maize cropping system in

China could be greatly increased by synergizing the management of soil P and

chemical P supply to maximize root/rhizosphere P efficiency. In China, this system

has been successfully approved, which could be a potential approach to ensuring

food security and improving P use efficiency and environmental quality for other

rapidly developing countries.

References: Shen J, Li C, Mi G, Li L, Yuan L, Jiang R, Zhang F (2013) Maximizing root/rhizosphere

efficiency to improve crop productivity and nutrient use efficiency in intensive agriculture of

China. J Exp Bot 64:1181–1192

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Effects of farmyard manure and soil characteristics on soil-plant P dynamics in

submerged rice

Tovohery Rakotoson1, Yasuhiro Tusjimoto2 1 Laboratoire des Radio-Isotopes, Université d’Antananarivo, BP 3383, Route d’Andraisoro, 101

Antananarivo, Madagascar. 2 Japan International Research Center for Agricultural Sciences (JIRCAS), 1-1 Ohwashi, Tsukuba,

Ibaraki 305-8686, Japan

Keywords: Farmyard manure, soil characteristics, isotope dilution

Phosphorus (P) deficiency is one of the major limiting factors for lowland rice

production in Madagascar. This P deficiency is because of high contents of P-fixing

iron (Fe) oxide minerals in soils. Although at subtle quantity, use of organic matter

(OM) can release fixed P in soils by promoting microbial reduction of Fe oxides under

submerged condition. Farmyard manure (FYM) is the main OM source of nutrient

input among smallholder farmers but its effects on soil-plant P dynamics in relation

to different soil characteristics has been little studied. This study aimed to assess

such FYM effects in relation to soil oxalate extractable P (Pox), pH and total C (TotC)

which were reported as important indicators of soil P availability in the region. An

experiment of submerged rice (Exp1) was conducted in greenhouse using 6 paddy

soils from Madagascar differing in Pox, pH and TotC content; and in a factorial

combination of FYM (0 and 20 g/kg) and mineral P (0 and 100 mg/kg as KH2PO4)

applications. A similar experiment (Exp2) using three soils selected from Exp1 and

where the soil available P was labelled with 32P (isotope dilution technique) was

additionally conducted to further investigate origin of P taken up by rice plants. In

Exp2, FYM (0 and13 g/kg) was compared with Triple Superphosphate (TSP) at equal

nominal P dose of 47 mg/kg. Exp1 confirmed that biomass yield responses to FYM (-

0.08 to 0.77 g/pot) and to mineral P (0.02 - 1.66 g/pot) applications showed

significant interactions with soil characteristics and were positively correlated with

shoot P content and P uptake (r2 respectively 0.73 and 0.88). Stepwise regressions

revealed that the effect of FYM applications on biomass and P uptake of rice was

smaller in soils with higher TotC and higher pH. Exp2 confirmed the results of Exp1

and further showed full substitution effect of TSP by FYM, i.e. biomass increases

were comparable between TSP and FYM applications in all three soils. The share of

total P taken up in rice shoot derived from soil native P was maximum under FYM

application (0.97 - 7.07 mg/pot) and was more pronounced under low TotC and pH

conditions. Such suggests that FYM unlocked soil P likely through extended Fe-oxides

reduction. In addition, rice plants took up more P from FYM in soils with lower pH.

Conclusions are that the extent of FYM application on improving P availability for

submerged rice via P input or/and soil P release will be likely to be larger under low

TotC and pH conditions.

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Deep-placing phosphorus in NE Australian grain soils: 1. Cumulative grain yield increased by 5-30%

David W. Lester1, Michael J. Bell2, Douglas J. Sands3 1Queensland Department of Agriculture and Fisheries, Toowoomba, QLD 4350

Australia. 2University of Queensland, Gatton, QLD 4343 Australia.

Keywords: Deep-placement, gross margin. Grain and pulse crops on Vertosols in the subtropical area of North Eastern Australia

utilise fallow rainfall stored in the soil profile as the basis for reliable production, with

rainfall summer-dominant and highly variable in intensity and amount. Climatic

conditions allow winter (spring wheat, chickpea) or summer (sorghum, mungbean)

crops, but sowing does not occur until sufficient moisture has been stored to reduce

risk of crop failure. Plant-available phosphorus (P) has stratified distribution: higher

concentrations in surface 0.0-0.1m but much lower supply below 0.1m. Plant roots

rarely exploit surface layers due to rapid evaporative losses, so an experimental

program commenced across Queensland in 2013 (16 sites) to see if deeper P

placement could improve plant P acquisition and deliver increased yield. Mono-

ammonium phosphate (MAP 10N 22P) was generally used as the P source at rates

from 0 to 60 kg P/ha. Placement was at ≈ 0.2m depth on ≈ 0.5m band spacing. Urea

(N), potassium chloride (K), ammonium sulfate (S) and zinc (Zn) where applied to

balance nitrogen input and provide basal nutrients. An untreated control was

included to benchmark deep applications against current district production.

Experiments have 4-6 replicates and responses quantified by grain yield. Results for

a subset of sites demonstrate increased yields and positive gross margin (Table 1).

Table 1 – Selected cumulative grain yield and gross margin changes relative to untreated

control

kg P/ha applied

0 10 20 30 60 (40 Dysart)

Wondalli (Sg-Wh-Cp-

Wh)*

Δ Yield (kg/ha) -88 (-1%)

460 (5.5%)

1225 (15%)

1482 (18%)

1769 (21%)

Gross margin ($/ha)+ -$11 $57 $305 $301 $326

Jimbour West

(By-Mg-Sg-Cp) *

Δ Yield (kg/ha) 914

(10%) 1227 (14%)

1648 (19%)

1658 (19%)

2065 (24%)

Gross margin ($/ha)+ $441 $510 $665 $593 $673

Dysart (Sg-Sg-Sg-

Cp) *

Δ Yield (kg/ha) 1113 (14%)

2169 (26%)

2786 (30%)

2811 (32%)

Gross margin ($/ha)+ $149 $659 $915 $737

*Sg = Sorghum, Wh = Wheat, Cp = Chickpea, By = Barley, Mg = Mungbean; +assuming Urea $400/t, MAP $800/t, Ammonium Sulfate $350/t, KCl $500/t, Zn $2000/t,

application $30/ha; sorghum $300/t, wheat $300/t, chickpea $800/t, barley $270/t, mungbean $1200/t.

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Combing tillage, basal nutrition (NKSZn) and deep P placement has substantially

increased grain yields across a series of experiments. Sites continue to respond after

4 crops and research determining response longevity continues. Economic analysis

(Zull et al. 2018) suggests positive economic returns after the second crop.

References Zull A, Cox H, et al. (2018) Long-term economics of placing phosphorus at depth in modern farming systems. PSP6 Symposium on Phosphorus in Soils and Plants, Leuven (BE)

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Different phosphorus acquisition traits for two wheat genotypes growing in an

acidic high P-fixing soil

Pedro Campos1,3, N. Aguilera, F. Borie, J. A. López-Ráez3, A. Seguel 1Doctoral program in Science of Natural Resources, Universidad de La Frontera, P.O. Box 54-D,

Temuco, Chile. 3Department of Soil Microbiology and Symbiotic Systems, Estacion Experimental

del Zaidin (EEZ-CSIC), Profesor Albareda 1, 18008 Granada, Spain

Keywords: Root architecture, organic acids, Pase activity, arbuscular mycorrhiza

Wheat (Triticum aestivum L.) is one of the most important food crops in the world

and the annual crop most harvest in Chile. However, wheat production is highly

dependent on phosphorus (P) fertilizers, which acquisition in general has low

efficiency. Breeding for P-efficient cultivars can be done by: i) improving internal P

use efficiency (PUE), and/or ii) enhancing P uptake from soil or P acquisition

efficiency (PAE). PAE is largely based on the physiological characteristics of the root

system that are summarized in Figure 1.

The aim of the present study was to evaluate P-acquisition root traits of two wheat

genotypes growing in an acidic high P-fixing Andisol. Plants were grown in rhizoboxes

for 8 weeks in a greenhouse with two fertilization ways: P (22 kg P.ha-1) applied

locally near the seeds or mixed with the soil. Plants without fertilization were used

as controls. Extraction disks were placed for 1 h at two root zones (near the tip and

near the crown) at 3, 5 and 7 weeks in order to collect and analyze the organic acids

exuded. At harvest, rhizosphere soil was also collected and acid phosphatase (Pase)

activity determined. Root architecture was analyzed with the software WinRHIZO,

and the natural arbuscular mycorrhizal (AM) community is being determined by RFLP

analysis. P addition did not affected shoot growth and P-acquisition in the less-

efficient (LE) genotype. In contrast, the efficient (E) genotype increased biomass

production and P-acquisition by almost 100% under localized P.

Shoot P concentration was not altered in any of the cultivars upon P addition,

although it was higher in the E genotype, highlighting its efficiency. Root architecture

was affected by P fertilization, being the highest responses observed in E, which

maintained the P acquired:root area ratio regardless of the soil P level. No

differences on Pase activity were found. Finally, oxalic acid (OA) concentration in the

exudates was lower in the localized P treatment for both genotypes. However, when

analyzing root zones, exudation of OA was higher near the root crown of E in the

localized P treatment compared to root tips. Interestingly, the opposite pattern was

observed in non-fertilized E roots.

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This capacity of differential exudation was not observed in the LE genotype, which

might have importance on signaling towards P solubilizing/mineralizing

microorganisms.

Figure 1. Strategies to improve P-acquisition: 1) changes in root architecture; 2) exudation of protons, organic acid anions, and Pase; and 3) root association with microorganisms, such as AM fungi.

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Hidden miners: soil-plant-microbe interactions for phosphorus

mobilization with cover crops

Moritz Hallama1, Carola Pekrun2, Hans Lambers3, Ellen Kandeler1

1 Soil Biology Section, Department of Soil Science and Land Evaluation, University of Hohenheim 2 Agronomy Section, Institute of Applied Agriculture, Nuertingen-Geislingen University

3 School of Biological Sciences and Institute of Agriculture, University of Western Australia,

Crawley (Perth), WA6009, Australia

Keywords: Conservation agriculture, nutrient cycling, plant-microbial interactions

In the light of the global issues of phosphorus (P) scarcity, expensive fertilizers and

environmental hazards, cover crops constitute a promising management option for

the sustainable intensification of agriculture, while improving crop P nutrition.

We conducted a meta-analysis to review the results of published field studies on

cover crops, P cycling, and the soil microbial community, and focused on publications

about the underlying mechanisms and plant-microbial interactions. Cover crops

benefit the P nutrition of main crops by distinct, simultaneous processes: soil P (from

different pools) is stored in the cover crop biomass, and the mineralization of P-rich

litter provides available P for the main crop. This pathway is most relevant for cover

crops with a high biomass, but the P concentration of the residues is critical for the

mineralization dynamics.

Cover crops enhance the soil microbial community, leaving a legacy of increased

microbial biomass P and phosphatase activity for the main crop, and increases in

arbuscular mycorrhizal abundance particularly in soils with low P availability.

However, cover crop effects on P availability can barely be detected by standard soil

P tests, except for Lupinus sp., which increase P availability even in the main crop

phase. Cover crops are generally more effective in systems low in available P, and

may access P pools of lower availability. The cover crop types have particular profiles

regarding their mechanisms of action (Fig. 1).

Agricultural management affects all these processes and can be used to improve

cover crop effects. In summary, cover cropping shows potential to tighten nutrient

cycling in agricultural systems under different conditions, increasing crop P nutrition

and yield.

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Figure 1: Radar plot summarising cover crop biomass characteristics, and effects on soil

biological properties and available P relative to fallow control treatments.

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Coping with drought: Plant roots maintain phosphatase activity in

drying soils by increasing water retention in the rhizosphere

Maire Holz1*, Mohsen Zarebanadkouki1, Andrea Carminati1, Jan Hovind2, Anders Kaestner2,

Marie Spohn3

1 Division of Soil Physics, Bayreuth Center of Ecology and Environmental Research (BayCEER),

University of Bayreuth, Germany; 2PPaul Scherrer Instiute, Villigen, Switzerland.;

3 Department of Soil Biogeochemistry, Bayreuth Center of Ecology and Environmental Research

(BayCEER), University of Bayreuth, Germany

Keywords: Phosphatase activity; enzyme diffusion; drought

Severe soil drying negatively impacts nutrient uptake and phosphatase activity in soil

and it is not clear how plant roots adjust to it. We propose that plants maintain high

phosphatase activity around roots during drought by retaining moisture in the

rhizosphere, which facilitates diffusion of exoenzymes and high rates of enzymatic

catalysis (Fig. 1a).

Barley plants were grown in rhizoboxes and subjected to a drying cycle. Soil water

content (WC) and phosphatase activity were monitored by neutron radiography and

soil zymography. Rhizosphere WC increased with soil drying relative to bulk soil WC

probably due to plant-derived mucilage. Phosphatase activity increased in the

rhizosphere compared to the bulk soil from a ratio of 10 at 40% WC to a ratio of 63

at 5% WC (Fig. 1b). Phosphatase activity and local soil WC were strongly correlated

(rhizosphere: R²=0.53, bulk: R²=0.63), indicating that diffusion controls soil

phosphatase activity.

We showed that exoenzyme activity in soil strongly depends on the local soil WC and

that by retaining water in the rhizosphere plants maintain high phosphatase activity

around roots under drought. This is beneficial for plants because the high WC of the

rhizosphere facilitates a high rate of phosphatase activity and P diffusion, and thus

plant P acquisition.

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Impacts of elevated CO2 on phosphorus fractions in Australian farming soils

Jian Jin1, Roger Armstrong2, Caixian Tang1 1Department of Animal, Plant and Soil Sciences, AgriBio, La Trobe University, Melbourne

Campus, Bundoora Vic 3086, Australia. 2Department of Economic Development, Jobs, Transport & Resources, Horsham, Vic 3401,

Australia.

Keywords: FACE, organic P, Crops

The long-term effect of elevated CO2 (eCO2) on phosphorus (P) biogeochemistry in

farming systems is largely unknown. An investigation into such an effect is essential

for the efficient P management in future climate change. We compared the effects

of eCO2 on P fractions in three farming soils in Southern hemisphere. A 7-year

experiment of free air CO2 enrichment (FACE) was conducted with a rotation of

wheat, field pea and canola grown in intact cores (0.3-m diameter) of Chromosol

(Luvisol), Vertosol (Vertisol) and Calcarosol (Calcic Xerosol) under ambient CO2

(aCO2) (390 ± 10 ppm) or eCO2 (550 ± 30 ppm). Elevated CO2 resulted in extra 134,

91 and 93 mg P core-1 removed as grain compared to aCO2 for Chromosol, Vertosol

and Calcarosol, respectively. It decreased the concentration of NaHCO3- and NaOH-

extractable inorganic P in all three soils with NaOH-extractable inorganic P

decreasing from 82 to 63 mg kg-1 in Chromosol, and 22 to 5 mg kg-1 in Vertosol but

not in Calcarosol. Elevated CO2 also decreased NaOH-extractable organic P by 20, 12

and 7 mg kg-1 in Chromosol, Vertosol and Calcarosol, respectively. A following

rhizobox experiment further demonstrated that eCO2 facilitated the mineralization

of an organic P compound (phytate), and increased microbial C/P ratio in the

rhizosphere of wheat in Vertisol. There results indicated that eCO2 favoured both

chemical mobilization of non-labile inorganic P and mineralization of organic P in the

soils. Elevated CO2 may fundamentally change the strategy of microbial access of

organic P in the rhizosphere of crops.

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Strategies in sustainable use of soil legacy phosphorus in the intensive

vegetable protected-field

Qing Chen, Bingqian Fan, Shuai Zhang, Shuo Chen

Beijing Key Laboratory of Farmland Soil Pollution Prevention-control and Remediation/College

of Resource and Environmental Sciences, China Agricultural University, No. 2 Yuanmingyuan

Xilu, Haidian, Beijing 100193, China

Keywords: Soil legacy phosphorus, protected-field, strategy, mobilization

China has the largest area of protected-field vegetable production in the world with

rapid development in the last three decades. Meanwhile, the rapid development of

the livestock industry and a large amount of livestock discharge to arable land has

resulted in an extreme surplus of nitrogen (N), phosphorus (P) in agricultural fields,

especially the protected-field for vegetable production. Additionally the excessive

use of imported and domestic-produced phosphorus fertilizer strengthened the P

accumulation in protected-field. Soil acidification induced by ammonium nitrogen

transformed from manure N mineralization and urea hydrolysis strongly changed soil

biochemical processes and increased the labile proportion of P through reducing the

capacity to fix and/or adsorb phosphates. Recent survey from literatures and field

investigation found that over 95% of soil labile P level had been over the

environmental P threshold. It should not be ignored that the P surplus in protected-

field was so obviously high that it has potentially degraded the water body quality.

Strategies to reduce the potential risk of phosphorus accumulation in the protected-

field system include: 1) Reducing the input of manure, and fertilizer through P

recommendation strategy and fertigation technique (i.e. starter P supply in

rootzone) ; 2) Using of low-cost adsorbents materials (PSM) with high P retention

capacity i.e. Ca-Mg-minerals, modified biochar etc. to stabilize the mobility of labile

legacy phosphorus in the intensively cultivated soil; 3) Fertigated functional

microbes/biostimulants in the rootzone to promote root growth and chelating agent

i.e. citric acid or humid acid for legacy P mobilization; 4)Rotating catch crop in

fallowing period to extract soil legacy phosphorus; 5) Integrated strategies of above-

mentioned techniques.

References

- Cusack PB, Healy MG, Ryan PC, Burke IT, Donoghue LMTO, Éva Ujaczki, Courtney R

(2018). Enhancement of bauxite residue as a low-cost adsorbent for phosphorus in aqueous

solution, using seawater and gypsum treatments. Journal of Cleaner Production 179: 217-224

- .

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The effect of coupling earthworms and residues on the availability of soil

phosphorus and plant growth in the highlands of Madagascar

Malalatiana Razafindrakoto1, Sariaka N. F. Raharijaona2, Eric Blanchart3 1 Laboratory of RadiosIsotopes, University of Antananarivo, BP 3383, 101 Antananarivo,

Madagascar. 2 Ecole Normale Supérieure, University of Antananarivo, Madagascar.

3 IRD, UMR Eco&Sols, 2 Place Viala, 34060 Montpellier, France

Keywords: Earthworms, organic matter quality, Ferralsols

Very low rice yields in Madagascar highlands requires the development of innovative

and adoptable strategies and practices such as the extension of the cultivated area

by colonizing hillsides or « tanety ». Unfortunately, the soils of these hillsides,

namely Ferralsols, are poor in nutrients, especially in plant-available phosphorus P.

The availability of P for plants is strongly related to soil richness in organic matter

and is regulated by biotic activities such as earthworms. As Malagasy farmers have

no access to fertilizers, there is a need to develop agroecological practices that

optimize organic resource and ecological processes in order to increase crop yields.

The objective of this study was to analyse the effect of the combination of different

earthworm species with different organic matters on soil P availability and plant

growth. Different combinations of earthworm species (Dichogaster saliens,

Amynthas minimus, Amynthas corticis, Pontoscolex corethrurus and Eudrilus

eugeniae) with compost, manure and different organic residues (Eleusine coracana,

Zea mays, Stylosanthes guyanensis and Desmodium uncinatum) were introduced in

soil samples. At the end of this experiment, i.e. after earthworms have consumed all

the soil, the soil available P content was measured. Then, to evaluate the effect of

each couple (earthworm + organic matter) on plant growth, we grew rainfed rice on

soils resulting from the previous experiment, during 28 days. The highest soil

available P content was measured in the treatment earthworm with manure and

with compost: between 8.21 and 11.40 mg P kg-1 depending on earthworm species.

In comparison, P available content in control soil was 5.30 mg P kg-1. Regarding the

rice growth, couplings with compost and manure showed the highest values,

irrespectively of earthworm species; we also observed a marked improvement in rice

growth with Desmodium residues coupled with any earthworm species.

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High nitrogen application favored organic phosphorus accumulation in P-rich

calcareous soil

Shuo Chen, Zhengjuan Yan, Shuai Zhang, Bingqian Fan, Qing Chen

College of Resources and Environmental Sciences, China Agricultural University, No. 2

Yuanmingyuan Xilu, Haidian, Beijing 100193, P. R. China.

Keywords: Nitrogen, organic phosphorus, microbial community structure

High nitrogen (N) fertilizers applied in the intensive agricultural field commonly

stimulated soil carbon (C) and N turnover and soil acidification (Han et al., 2015;

Treseder, 2008; DeForest et al., 2004). Whereas their influences on the

transformation of soil organic phosphorus (Po) were unknown, which is fundamental

to understanding the availability and movement of soil Po.

In this study, the N fertilizer (i.e., urea) application at the rates of 876 (N1) and 1688

(N2) kg N ha-1 a-1, to influence Po transformation in a calcareous soil were

investigated in a 13-year field trial. High rate of urea (N2) significantly increased soil

total Po content and proportion.

Urea application significantly increased the proportions of NaOH-Po (i.e., Fe- and Al-

associated P) by 146-154% determined with chemical fractionation and the

proportion of orthophosphate diesters by 22.3-29.0% in Pt determined with 31P

NMR. Meanwhile, high rate of urea (N2) significantly increased the proportions of

phosphonates and pyrophosphate while decreased orthophosphate proportion in

Pt. Soil pH, CaCO₃, the sum of Mehlich-3 extractable Ca and Mg, microbial biomass C

(MBC), and alkaline phosphatase (ALP) activity had significant effects on the

compositions of soil P (ADONIS, P<0.05). High rate of urea (N2) application

significantly decreased pH, CaCO₃, Mehlich-3 extractable Mg and ALP activity,

increased MBC and relative abundance of dominant phylum, Proteobacteria, in both

of total bacterial and phoD-harboring bacterial communities. These showed that

urea application affected both abiotic and biotic processes of Po transformation. Soil

acidification induced by urea application results in the increase of Po bounded by Al

and Fe hydroxides/oxides (i.e., NaOH-Po).

Both the increase in P immobilization and decrease in P biochemical mineralization

contributed to the Po accumulation under high N input. Soil pH was the main factor

that explained 79.4% and 34.2% of the total bacterial and phoD-harboring bacterial

communities in phylum level, respectively. Soil pH and CaCO₃ contents could explain

50.3% and 23.9% of the total variances observed in the compositions of P forms.

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Therefore, high urea application largely affected soil Po forms through changing soil

pH, which consequently influenced on soil Po transformation with both abiotic and

biotic processes in P-rich calcareous soil.

References

- DeForest JL, Zak DR, Pregitzer KS, Burton AJ (2004) Atmospheric nitrate deposition, microbial

community composition, and enzyme activity in northern hardwood forests. Soil Sci. Soc. Am.

J. 68:132–138.

- Han J, Shi J, Zeng L, Xu J, Wu L (2015) Effects of nitrogen fertilization on the acidity and

salinityof greenhouse soils. Environ Sci Pollut Res 22:2976–2986.

- Treseder KK (2008) Nitrogen additions and microbial biomass: a meta-analysis of ecosystem

studies. Ecology Letters 11: 1111–1120.

302 | PSP6

Author Index

A Abel S, 118 Agesa B, 247 Amery F, 38 Amy C, 193 Ana Luengo Escobar, 257 Andriamananjara A, 51 Asaeda S, 161 Azeez M O, 68

B Barbarić M, 210 Barciszewska-Pacak M, 196 Bauters M, 223 Bilyera N, 162 Blackwell M, 69 Bogdan A, 228 Braun S, 97 Brod E, 57 Brown L K, 216 Bruno Ringeval, 231

C Campos P, 281 Caspersen S, 253 Cassidy R, 215 Celi L, 127 Ceulemans T, 224 Chen Q, 110, 286 Chen S, 83, 288 Chen X X, 251, 252 Christensen J T, 74 Chun-Qin Zou, 252 Cornelis J T, 32 Cozzolino V, 104 Crombez H, 155 Crush J, 164 Cruz-Paredes C, 43

D Daku E, 226 Daoui K, 242 Darch T, 218

De Bauw P, 129 Degryse F, 261 Demanet R, 257 Dox K, 238 Duboc O, 100

E Eichler-Löbermann B, 101 Erel R, 185 Everaert M, 220

F F.J.T. van der Bom, 28 Fan B, 90 Feng G, 42 Fetze J, 267 Fraser T D, 187 Furutani H, 45

G Gao L, 202 Gao Y, 259 Garaycochea S, 87 García-Sánchez M, 40 García-Velázquez L, 135 Garland G, 75 George T S, 154, 216 Granger S J, 76 Grigatti M, 229 Gruau G, 211 Gu S, 263 Gunji K, 179 Guppy C, 130 Gustafsson J P, 81

H Halicki S, 189 Haling R E, 22 Hallama M, 282 Hamdi A, 262 Hauenstein S, 254 Haygarth P M, 212 Helfenstein J, 52 Herr C, 266 Herschbach C, 199 Higo M, 178 Hoang K T K, 79

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Hoffland E, 134 Holz M, 283 Hong-Zhe L, 146 Honvault N, 145 Hothorn M, 114 Houot S, 107 Hsieh Y F, 197 Huang J, 99

J Janssens I A, 221 Jarosch K A, 166 Jarosch K A, 133 Jate E, 180 Jiang J, 110 Jin J, 285 Jing J, 240

K Kaňa J, 84 Katoh M, 236 Kavka M, 142 Kehler A, 92 Kinoshita R, 36 Krüge I, 265 Ksheem A M A, 268 Kvakić M, 194, 231

L Leinweber P, 77 Lester D, 239 Lester D L, 245 Lester D W, 246 LesterD W, 280 Li H Z, 62 Li L, 174 Li Q, 78 Lo Presti E, 244 Luengo Escobar A, 258

M Maranguit D, 94 María de la Luz Mora, 257, 258 Marlys Andrea Ulloa, 204 Martens S, 230 Maruyama H, 190 Masayuki T, 64

McLaren T, 26 Mercier C, 198 Messiga A J, 105 Mettler-Altmann T, 121 Mezeli M, 41 Michelini D, 172 Millaleo R, 182 Miyajima N, 175 Mongol N, 255 Mora M L, 102, 176 Motte H, 139

N Nakamura S, 233 Nawara S, 35 Nguyen N N, 152 Nichols S, 153 Nishigaki T, 55 Njoroge S, 276 Nobile C, 140 Nussaume L, 160

O Oberson A, 124 Okamura T, 169

P Paredes C, 248 Patra D D, 109 Peng Y, 95 Peñuelas J, 222 Peterson H, 214 Pfahler V, 63 Pistocchi C, 30 Poblete-Grant P, 256 Poon D, 106 Prochnow L, 227 Pypers P, 274

Q Qing-Fang B, 148

R Rahman S, 66 Rakotoson T, 279 Rasheed M S, 50 Razafindrakoto M, 287

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Redouan Q, 171 Reusser J E, 72 Rinasoa S, 243 Riyazaddin M, 200 Ros M B H, 271 Roschitz C, 122 Rose T, 93

S Saito M, 186 Santoro V, 85 Schaap K J, 132 Schneider M, 188 Schryer A, 33 Schwerdtner U, 151 Sega P, 195 Shen J, 278 Shi L, 201 Shimamura E, 192 Siegenthaler M, 70, 157 Simpson R J, 217 Singh A L, 191 Singh D, 121 Stevenel P, 59 Stutter M, 235 Sugihara S, 163

T Tahovská K, 54 Tandy S, 80 Tatewaki Y, 181 Tawaraya K, 126 Tchuisseu Tchakounté G V, 159 Turner B L, 207 Tweedie A, 91

V Valeska Pontigo S, 204 Van Dael T, 112 Van der Bom F J T, 28 Van der Wal A, 264 Vandecasteele B, 241 Vandermoere S, 65 Verbeeck M, 272 Vermeiren C, 111 Vieira B, 67 Vogel C, 53

Vos H M J, 136

W Wang X, 259 Wang Y, 138 Wang Y P, 269 Warrinnier R, 210 Wasaki J, 167 Widdig M, 147 Willekens K, 183 Wissuwa M, 115, 203 Withers P J A, 206

Y Yang S Y, 23 Ylivainio K, 277

Z Zacher A, 96 Zeng F, 58 Zhang L, 48, 143 Zhang S, 89 Zhang W, 165 Zhu J, 119 Zicker T, 237 Zou C, 249

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