SOIL COSOIL CO22 AND N AND N22O EMISSIONS FROM AN O EMISSIONS FROM AN

AGRICULTURAL WATERSHED AS INFLUENCED BY AGRICULTURAL WATERSHED AS INFLUENCED BY LANDSCAPE POSITION AND AGROFORESTRY LANDSCAPE POSITION AND AGROFORESTRY CONSERVATION MANAGEMENT PRACTICESCONSERVATION MANAGEMENT PRACTICES

Neal J. BaileyNeal J. BaileyDepartment of Soil, Environmental, and Department of Soil, Environmental, and

Atmospheric SciencesAtmospheric Sciences

IntroductionIntroduction

Agroforestry is the practice of intentionally Agroforestry is the practice of intentionally growing woody plants within a cropping system growing woody plants within a cropping system and is reputed for having economical and and is reputed for having economical and environmental benefits environmental benefits

The agroforestry system along with the grass The agroforestry system along with the grass contour strips were established in 1997 on the contour strips were established in 1997 on the Greenley watershed siteGreenley watershed site

Greenley Paired Watershed

GR

AF

CR

Vegetative filter strips increase nutrient Vegetative filter strips increase nutrient retention and infiltration rates (Udawatta et al. retention and infiltration rates (Udawatta et al. 2002; Garrity 2004)2002; Garrity 2004)

Agroforestry and grassland systems accumulate Agroforestry and grassland systems accumulate soil organic matter over time (Kaur et al. 2000; soil organic matter over time (Kaur et al. 2000; Corre et al. 1999)Corre et al. 1999)

Carbon and nitrogen are major constituents of Carbon and nitrogen are major constituents of soil organic matter (Sharrow and Ismail 2004)soil organic matter (Sharrow and Ismail 2004)

IntroductionIntroduction

IntroductionIntroduction

Agroforestry and grass filter strips may Agroforestry and grass filter strips may contribute to the mitigation of the increased contribute to the mitigation of the increased levels of atmospheric carbon dioxide (COlevels of atmospheric carbon dioxide (CO22), and ), and

reduce the levels of nitrous oxide (Nreduce the levels of nitrous oxide (N22O) O)

production production

Research regarding the effects of landscape Research regarding the effects of landscape

position and temperate conservation position and temperate conservation management practices on the efflux of COmanagement practices on the efflux of CO22 and and

NN22O in an agricultural watershed is limitedO in an agricultural watershed is limited

IntroductionIntroduction

Atmospheric concentrations of COAtmospheric concentrations of CO22 and N and N22O have increased considerably since 1750O have increased considerably since 1750

COCO22 has increased approximately 31% has increased approximately 31%From ca. 280 ppm to 360 ppmFrom ca. 280 ppm to 360 ppm

NN22O has increased approximately 17%O has increased approximately 17%From ca. 270 ppb to 315 ppb (IPCC, 2001)From ca. 270 ppb to 315 ppb (IPCC, 2001)

IntroductionIntroduction

All soils produce both COAll soils produce both CO22 and N and N22O through the nutrient cycling processO through the nutrient cycling process

However, the production rates can be exacerbated by agricultural practicesHowever, the production rates can be exacerbated by agricultural practicesCOCO22 – tillage and drainage – tillage and drainage

NN22O – application of fertilizer N O – application of fertilizer N

Major sources of soil CO2

Major sources of soil CO2

Plant root respirationPlant root respiration Corn field between 7- 43 percent of total soil Corn field between 7- 43 percent of total soil

respiration (Rochette et al. 1999)respiration (Rochette et al. 1999) Tall Grass Prairie and pasture grass 40 and 53 Tall Grass Prairie and pasture grass 40 and 53

percent, respectively (Kucera and Kirkham, percent, respectively (Kucera and Kirkham, 1971; Robertson et al., 1995)1971; Robertson et al., 1995)

Oak forest 52 percent (Kelting et al., 1998)Oak forest 52 percent (Kelting et al., 1998)

Major Pathways of Soil N2O Formation

NO3- NO2

- NO N2O N2

Denitrification

Nitrification

NH4+ NH2OH

N2O

[HNO]

NO

NO2- NO3

-

NO2NHOH

N2O

Linn and Doran (1984)

Objectives

Determine the effects of landscape position and Determine the effects of landscape position and conservation management practices on:conservation management practices on: Efflux rates of COEfflux rates of CO22 and N and N22OO Distribution of total soil carbon and nitrogenDistribution of total soil carbon and nitrogen

Establish potential of soils collected in each Establish potential of soils collected in each watershed for production of COwatershed for production of CO22 and N and N22O under O under

controlled laboratory conditions controlled laboratory conditions

Materials and Methods- FieldMaterials and Methods- Field

Paired watersheds, Greenley Research Station in northeast MissouriPaired watersheds, Greenley Research Station in northeast Missouri Management system in each watershed:Management system in each watershed:

Cropped-only (CR)Cropped-only (CR) Cropped, interspersed with grass contourCropped, interspersed with grass contour

strips (GS)strips (GS) Cropped, interspersed with grass-tree contour Cropped, interspersed with grass-tree contour strips (AF)strips (AF)

Landscape positions within each watershed were: summit, backslope, and footslope Landscape positions within each watershed were: summit, backslope, and footslope

Materials and Methods- FieldMaterials and Methods- Field Surface soil COSurface soil CO2 2 efflux was measured in the field efflux was measured in the field

by using a portable infrared COby using a portable infrared CO22 analyzer fitted analyzer fitted

with a closed chamberwith a closed chamber NN22O efflux was measured with a Buck Scientific O efflux was measured with a Buck Scientific

Model 910 gas chromatograph equipped with an Model 910 gas chromatograph equipped with an electron capture detector (ECD) after soil surface electron capture detector (ECD) after soil surface NN22O samples were collected in vacuum storage O samples were collected in vacuum storage

bottles and transported from the field bottles and transported from the field

Gas flux sampling occurred from April to Gas flux sampling occurred from April to October, 2004 before and after N fertilizer October, 2004 before and after N fertilizer applicationapplication

Soil water content and temperature were Soil water content and temperature were determined at the 0 to 5 cm depth at each COdetermined at the 0 to 5 cm depth at each CO22

and Nand N22O efflux measurement O efflux measurement

Materials and Methods- FieldMaterials and Methods- Field

The incubation was conducted for 43 days with The incubation was conducted for 43 days with packed cores at a bulk density of 1.2 g cmpacked cores at a bulk density of 1.2 g cm -3-3

Treatments for incubation:Treatments for incubation: Management soils (GR, CR, and AF)Management soils (GR, CR, and AF) WWater-filled pore space of 40, 60, 80, and 100 ater-filled pore space of 40, 60, 80, and 100 percentpercent

Nitrogen rate equivalent to the field application Nitrogen rate equivalent to the field application of 180 kg N haof 180 kg N ha-1 -1 (0.6g KNO(0.6g KNO33

- - core core-1-1) or 0g KNO) or 0g KNO33--

corecore-1-1

Materials and Methods- IncubationMaterials and Methods- Incubation

Total organic C Total N Bulk density Landscape position GS AF C Landscape position GR AF CR GS AF C GR AF CR GR AF CR

----------- % ----------- ---------------------------- % % ----------- ------------------------ Mg mMg m--3 3 -----SummitSummit 1.95 2.45 1.95 0.187 0.246 0.164 1.16 1.07 1.22 BackslopeBackslope 2.25 2.35 2.20 0.220 0.245 0.187 1.11 1.02 1.16 FootslopeFootslope 2.6 2.4 1.9 2.55 2.40 1.85 0.233 0.221 0.145 1.12

1.09 1.23

Distribution of Soil Properties- FieldDistribution of Soil Properties- Field

Total organic C Total N

LSD(0.05) -------- 0.28 --------- -----------0.051-----------

Two transects were sampled in November of 2003 in Two transects were sampled in November of 2003 in each watershed to determine Deach watershed to determine Dbb, TN, and TC, TN, and TC

LSD(0.10) ----------0.10-----------

0 40 80 120 160

AF BSCR BSGR BS

0

40

80

120

160

0 40 80 120 1600

40

80

120

160

% Water-Filled Pore Space- Field% Water-Filled Pore Space- Field%

WF

PS

% W

FP

S

DAA

DAA

LSD (0.05)

Summit Backslope

Footslope

NSNSNSNSNS NSNS NS NSNS NS NS

NSNS NSNSNSNS NS NS NSNS

%WFPS = (%w)(ρb)/(1- ρb /ρs)

Surface COSurface CO22 Flux - Field Flux - FieldC

O2

eff

lux

((µµ

mo

l m

mo

l m

-- 22se

cse

c-- 11))

CO

2e

fflu

x ((

µµm

ol

mm

ol

m-- 22

sec

sec-- 11

))

0 40 80 120 160

0

10

20

30

0

10

20

30 Summit Backslope

Footslope

Days after N application

NSNS NS NS NS NSNS NSNS NS NS

NSNS NS NS NS NS NS NS NS NS

NSNS NS NSNS NS NS NS

DNMRT(0.05)

Grass-tree contour strip Cropped-only Grass contour strip

Grass-tree contour strip Cropped-only Grass contour strip

Cumulative CO2 - Field

LSD(0.05)

Estimated microbial contribution

Accumulated CO2

Management Management

DAA

CO

2 f

lux

(µm

ol

m-2 s

ec-1)

kg C

O2-C

m-2

11

22

33 33

22

11

1010

2020

3030

00 4040 8080 120120 160160

NS NS NSNSNSNSNSNS

LSD(0.10)

Landscape position

Accumulated CO2

kg C

O2-C

m-2

33

22

11

LSD(0.05)

Surface NSurface N22O Flux- FieldO Flux- Field

Days after N application

0

400

800

Grass-tree contour strip Cropped-only Grass contour strip

0

400

800

Summit Backslope

Footslope

N2O

eff

lux

(g

N(g

N22OO

-- N h

aN

ha-- 11

da

yd

ay-- 11

))N

2O

eff

lux

(g

N(g

N22OO

-- N h

aN

ha-- 11

da

y

da

y -- 11

))

NS NS NS NS NS NS NS NS

NS NSNS NS NS NS NS NSNSNSNSNSNS

DNMRT(0.05)

0 40 80 120 160

NS NS NS NS NS NSNS

Cumulative N2O- Field

N2O

flu

x (g

N2O

-N h

a-1 d

ay-1)

DAA

Management

kg N

2O

-N h

a-1

10

20

30Accumulated NAccumulated N22OO

LSD(0.05)

Landscape position

Accumulated NAccumulated N22OO

10

20

30

LSD(0.05)

0 5 10 15 20 25

CO2 Flux- Incubation

DAYDAY DAYDAY

CO

CO

22 e

fflu

x (

mg

CO

eff

lux

(m

g C

O22-

C k

g-C

kg

-1-1 s

oil

Da

y s

oil

Da

y-1-1))

80% WFPS

60% WFPS40% WFPS

100% WFPS

LSD (0.05)

CO

CO

22 e

fflu

x (

mg

CO

eff

lux

(m

g C

O22-

C k

g-C

kg

-1-1 s

oil

Da

y s

oil

Da

y-1-1))

N2O Flux- Incubation

0

20

40

60

80

100

AF NAF NO NCR NCR NO NGR NGR NO N

0

400

800

1200

1600

0 5 10 15 20 25

0

4000

8000

12000

0 5 10 15 20 25

0

2000

4000

6000

LSD (0.05)

DAYDAY

NN22O

eff

lux

(O

eff

lux

(µ

gN

µg

N22O

-N k

g s

oil

O-N

kg

so

il-1-1 D

ay

Da

y-1-1))

NN22O

eff

lux

(O

eff

lux

(µ

gN

µg

N22O

-N k

g s

oil

O-N

kg

so

il-1-1 D

ay

Da

y-1-1))

DAYDAY

NS NS NS NS NS

80% WFPS

40% WFPS 60% WFPS

100% WFPS

CO2 and N2O Accumulated- Incubation

CO2 N2O

% WFPS % WFPS

LSD (0.05)

mg

Nm

g N

22O-N

kg

so

ilO

-N k

g s

oil-1-1

15

30

60

45

mg

CO

mg

CO

22-C

kg

so

il-C

kg

so

il-1-1

400

800

1200

80 1006040 80 1006040

Both landscape position and management Both landscape position and management system affected soil COsystem affected soil CO22 and N and N22O fluxO flux

Possible factors affecting differences in flux Possible factors affecting differences in flux were spatial and temporal variation in soil water-were spatial and temporal variation in soil water-filled pore space, distribution of soil total filled pore space, distribution of soil total organic C, total N, applied N fertilizer, and water organic C, total N, applied N fertilizer, and water extractable organic carbonextractable organic carbon

Improved understanding of these factors will Improved understanding of these factors will assist in predicting and managing greenhouse assist in predicting and managing greenhouse gas flux in agricultural watershedsgas flux in agricultural watersheds

ConclusionsConclusions

MU Center for AgroforestryMU Center for Agroforestry Dr. Peter MotavalliDr. Peter Motavalli Dr. Robert Kremer, USDA-ARSDr. Robert Kremer, USDA-ARS Greenley Research Center (Dr. Kelly Nelson, Greenley Research Center (Dr. Kelly Nelson,

Randall Smoot and Matt Jones) Randall Smoot and Matt Jones) Dr. Ranjith UdawattaDr. Ranjith Udawatta Dr. Mark EllersieckDr. Mark Ellersieck Eduardo NavarroEduardo Navarro Dr. Stephen AndersonDr. Stephen Anderson Dr. Randall Miles and Steve TroesserDr. Randall Miles and Steve Troesser

AcknowledgementsAcknowledgements