Assessing Soil Biological Activity as an Indicator of …sarc.calpoly.edu/pdfs/events/2017 Field...
Transcript of Assessing Soil Biological Activity as an Indicator of …sarc.calpoly.edu/pdfs/events/2017 Field...
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Alan FranzluebbersEcologist, Raleigh NC
Assessing Soil Biological Activityas an Indicator of Soil Health
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The problem
$N2O
Fossil-fuel energy
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The reality
Available Nitrogen (kg ha-1)
RelativeYield
(fraction)
0.0
0.2
0.4
0.6
0.8
1.0Assume 200 bu/a corn- grain with 1.5% N = 168 lb N/a- stover with 1.0% N = 112 lb N/a- total N need is 280 lb N/a
From 412 samples in NC- inorganic N = 57 + 78 lb N/a (0-12” depth)
Might assume the difference would be from inorganic fertilizer input
- organic N = 4532 + 2877 lb N/a
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Nitrogen availability to cropsFertilizer –>
.Surface-soil inorganic N
.
Surface
1’ depth
2’ depth
3’ depth
4’ depth
.
.
.
.
.Deep-profile
residual inorganic N......
Mineralizable nitrogen
a.ka. biologically active nitrogen
Loss mechanismsRunoffLeachingVolatilizationDenitrification
Limits to availabilitySoil temperatureSoil moistureRoot accessibilityBinding to claysBinding to organic matter
Additional inputsBiological N fixationCompostPrecipitation / dustIrrigation water
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What is soil biology
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http://www.chromographicsinstitute.com/2013/02/some-notes-about-soil-frdr-elaine-ingram/
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Surface residues important
Roots important
Fueling soil biological activity
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What do soil organisms need?
Suitable habitat Something to hold onto Water Oxygen Balanced pH
Carbon sources to consumeAccess to nutrients
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Fractions of soil organic carbon
Total Organic C
Particulate Organic C
SMBC
CMIN PlantResidue C
} Active
} Slow
} Resistant
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Soil microbial activity biologically sequesters N into
organic matter
Nitrogen and carbon mineralization have a complex relationship in the short-term…
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Soil Organic Carbon Accumulation (lb C / acre / year)0 250 500 750 1000
Soil OrganicNitrogen
Accumulation(lb N / acre / year)
0
25
50
75
100
Hayed bermudagrassHayed bermudagrass
Unharvested grass (CRP)
Hayed bermudagrass
Unharvested grass (CRP)
Grazed lightly to moderately
Hayed bermudagrass
Unharvested grass (CRP)
Grazed lightly to moderately
Soil organic C and N are closely associated in the long- term
Franzluebbers and Stuedemann (2010) Soil Sci. Soc. Am. J. 74:2131-2141
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Franzluebbers et al. (1995) Soil Sci. Soc. Am. J. 59:1618-1624
…most farm fields will be in some steady-state condition due to family-farm management
Thus, balancing the short- and long-term effects
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Soil process relationships
Franzluebbers et al. (1999) Soil Sci. Soc. Am. J. 64:613-623
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Days of Incubation0 7 14 21 28
CumulativeCarbon
Mineralization(mg . kg-1 soil)
0
100
200
300
400
5000-10-cm depth
10-20-cm depth
20-30-cm depth
The flush of CO2 following rewetting of dried soil
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…reveals the soil’s underlying biological and sustainable yield
…possible to reduce nutrient inputs and improve yield sustainability
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Preliminary results – all sites
Variable WatkinsvilleGA
ColumbiaMO
MandanND
ScottsbluffNE
BrookingsSD
Flush of CO2 75 21 58 13 5
CMIN0-24 d 95 6 108 9 9
SMBC 43 6 14 7 2
POXC 14 10 18 6 5
Protein 1 1 9 1 0
Treatment F value
Variable WatkinsvilleGA
ColumbiaMO
MandanND
ScottsbluffNE
BrookingsSD
Flush of CO2 10 11 14 16 10
CMIN0-24 d 8 19 10 19 10
SMBC 15 25 21 25 22
POXC 17 11 9 18 11
Protein 59 69 23 87 50
Coefficient of variation (CV, %)
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Days of Incubation0 7 14 21 28
CumulativeCarbon
Mineralization(mg . kg-1 soil)
0
100
200
300
400
5000-10-cm depth
10-20-cm depth
20-30-cm depth
Some key considerations
Representative sample of field of influence
Defined soil depth
Oven-dried sample (55 °C, 3 d)
Sieved coarsely to <4.75 mm
Rewetted to 50% WFPS
Accurate determination of CO2 – alkali trap / titration
The flush of CO2 following rewetting of dried soil
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Data from Franzluebbers et al. (2007) Soil Till. Res. 96:303-315
The flush of CO2 is an indicator of soil microbial activity
Flush of CO2 following Rewetting of Dried Soil(mg CO2-C
. kg-1 soil)0-3 d
0 100 200 300 400 500 600
BasalSoil
Respiration(mg CO2-C
. kg-1 soil . d-1)
0
10
20
30
40
50BSR = -2.3 + 0.07 * Flushr2 = 0.96
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Data from Jangid et al. (2008, 2010, 2011) Soil Biol. Biochem. 40:2843-2853; 42:302-312; 43:2184-2193
The flush of CO2 relates well to soil microbial biomass C
Flush of CO2 following Rewetting of Dried Soil(mg CO2-C
. kg-1 soil)0-3 d
0 100 200 300 400 500
SoilMicrobial
Biomass C(mg . kg-1 soil)
0
300
600
900
1200
1500SMBC = 162 + 2.45 * Flushr2 = 0.76
Georgia
Kansas
Michigan
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Flush of CO2 following Rewetting of Dried Soil(mg CO2-C
. kg-1 soil)0-3 d
0 200 400 600 800
Net NitrogenMineralization(mg . kg-1)0-24 d
0
50
100
150
200
>30% clay contentNMIN = 2.2 + 0.245*Flushr2=0.79, n=116
>30% clay contentNMIN = 2.2 + 0.245*Flushr2=0.79, n=116
20-30% clay contentNMIN = 1.8 + 0.275*Flushr2=0.83, n=172>30% clay contentNMIN = 2.2 + 0.245*Flushr2=0.79, n=116
20-30% clay contentNMIN = 1.8 + 0.275*Flushr2=0.83, n=172
<20% clay contentNMIN = 5.6 + 0.237*Flushr2=0.63, n=123
>30% clay contentNMIN = 2.2 + 0.245*Flushr2=0.79, n=116
20-30% clay contentNMIN = 1.8 + 0.275*Flushr2=0.83, n=172
<20% clay contentNMIN = 5.6 + 0.237*Flushr2=0.63, n=123
Across all soil texturesNMIN = 2.4 + 0.263*Flushr2=0.80, n=411
Data from M.R. Pershing (2016) NC State thesis
From multiple locations and depths within 61 different fields throughout North Carolina
The flush of CO2 shows association with N availability
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Available Nitrogen (kg ha-1)
RelativeYield
(fraction)
0.0
0.2
0.4
0.6
0.8
1.0
Goal of enlarging the biologically active N pool without causing
N leakage
Inorganic nitrogen Surface soil Residual in profile
Organic nitrogen Long-term stable Biologically active
Accounting for
Available Nitrogen (kg N ha-1)
Idealized response to nitrogen
Sites with low N availability and high N fertilizer response
Farm profit
Sites with high N availability and low N
fertilizer response
Environmental impact
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Not all fields have the same available N
Available Nitrogen (kg ha-1)
RelativeYield
(fraction)
0.0
0.2
0.4
0.6
0.8
1.0
Inorganic nitrogen Surface soil Residual in profile
Organic nitrogen Long-term stable Biologically active
Accounting for
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Consider this evidence…Plant N uptake in semi-controlled greenhouse experiments
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Plant dry matter production in minor relationship with total organic C
Pershing (2016) NC State University MS thesis
Soil from 30 sites in NC + VA(0-10, 10-20, 20-30 cm depths each)
Total Organic Carbon(g C . kg-1 soil)
0 10 20 30 40 50 60 70
PlantDry MatterProduction
(mg DM . g-1 soil)
0
2
4
6
8
DM = 2.2 + 0.041 (TOC)r2 = 0.22
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Plant dry matter production with no relationship to humic matter
Humic Matter(g . 100 g-1 soil)
0 2 4 6 8 10
PlantDry MatterProduction
(mg DM . g-1 soil)
0
2
4
6
8DM = 2.9 + 0.006 (HM)r2 = 0.00
from NCDA labPershing (2016) NC State University MS thesis
Soil from 30 sites in NC + VA(0-10, 10-20, 20-30 cm depths each)
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Plant dry matter production in moderate relationship with residual inorganic N
Residual Inorganic Nitrogen(mg NH4-N + NO3-N
. kg-1 soil)
0 20 40 60 80 100
PlantDry MatterProduction
(mg DM . g-1 soil)
0
2
4
6
8
DM = 2.2 + 0.060 (RIN)r2 = 0.33
Pershing (2016) NC State University MS thesis
Soil from 30 sites in NC + VA(0-10, 10-20, 20-30 cm depths each)
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Plant dry matter production in strong relationship with net N mineralization
Net N Mineralization(mg N . kg-1 soil)0-24 d
0 40 80 120 160
PlantDry MatterProduction
(mg DM . g-1 soil)
0
2
4
6
8
DM = 1.6 + 0.031 (NMIN)r2 = 0.76
Pershing (2016) NC State University MS thesis
Soil from 30 sites in NC + VA(0-10, 10-20, 20-30 cm depths each)
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Plant N uptake in strong relationship with plant available N
Plant Available Nitrogen(residual inorganic + mineralizable)
(mg N . kg-1 soil)0-24 d
0 50 100 150 200
PlantNitrogenUptake
(mg N . kg-1 soil)
0
50
100
150
200PNU = 6.2 + 0.55 (PAN)r2 = 0.89
Pershing (2016) NC State University MS thesis
Soil from 30 sites in NC + VA(0-10, 10-20, 20-30 cm depths each)
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The flush of CO2 in strong relationship with plant available N
Plant Available Nitrogen(residual inorganic + mineralizable)
(mg N . kg-1 soil)0-24 d
0 40 80 120 160 200
Flushof CO2
FollowingRewetting
of Dried Soil(mg C . kg-1 soil)0-3 d
0
200
400
600
800Flush CO2 = -23 + 3.2 (PAN)r2 = 0.88
Pershing (2016) NC State University MS thesis
Soil from 30 sites in NC + VA(0-10, 10-20, 20-30 cm depths each)
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Plant N uptake in strong relationship with the flushof CO2
Flush of CO2 Following Rewetting of Dried Soil(mg CO2-C
. kg-1 soil)0-3 d
0 200 400 600 800
PlantNitrogenUptake
(mg N . kg-1 soil)
0
50
100
150
200PNU = 12 + 0.16 (Flush)r2 = 0.88
Pershing (2016) NC State University MS thesis
Soil from 30 sites in NC + VA(0-10, 10-20, 20-30 cm depths each)
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Field calibration to N requirements
Example of 3 strips fertilized with 0, 69, and 125 kg N ha-1 at sidedress
- Corn grain and silage in North Carolina and Virginia
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Location of corn N trials
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1 2 3 4
Soil sampling- 8 cores from each of 4 replicate locations
Soil analysesFlush of CO2, net nitrogen mineralizationRoutine soil testing for pH, P, K, other elements (NC Dept Agric)Bulk density, particle size, total C-N, microbial biomass C, inorganic N
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Rep 4Rep 3Rep 2Rep 1
1140’
84
0’
Rockingham Co VA – 2016MD
North field(conventional)
South field(biological)
32-row strips of each sidedress N rate
0 N
140 N
70 N
0 N
70 N
140 N
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Cost-return scenarios
Condition
Thresholdreturn
needed(lb grain/lb N)
Low N ($0.50/lb N) and high grain ($5.60/bu) 5
Low N ($0.50/lb N) and low grain ($2.80/bu) 10High N ($1.00/lb N) and high grain ($5.60/bu) 10
High N ($1.00/lb N) and low grain ($2.80/bu) 20
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Nitrogen Rate (lb N/a)(at sidedress)
0 50 100 150
CornGrainYield(bu/a)
125
150
175
200
Rep 1
Rockingham Co VA – 2016MD North field (conventional)
Optimum N(lb N/a)
ThresholdL M H5 10 20
140 140 108
Rep 2
140 140 0
Rep 3
140 140 0
Rep 4
140 140 112
Average
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Rockingham Co VA – 2016MD South field (biologicals)
Optimum N(lb N/a)
ThresholdL M H5 10 20
Nitrogen Rate (lb N/a)(at sidedress)
0 50 100 150
CornGrainYield(bu/a)
150
175
200
225
250
Rep 1
140 140 0
Rep 2
140 140 0
Rep 3
140 140 0
Rep 4
69 53 36
Average
140 122 28
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Yield data from across farms in NC and VA
Total of 36 fields in NC + VA
Flush of CO2 (mg CO2-C . kg-1 soil)0-3 d
0 200 400 600 800
RelativeCorn Grain Yield
withoutSidedress N
(fraction)
0.0
0.2
0.4
0.6
0.8
1.0
r2 = 0.64n = 32
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Total of 32 grain fields in NC + VA and 11 silage fields in VA
Similarity in yield response between both grain and silage
Flush of CO2 (mg CO2-C . kg-1 soil)0-3 d
0 200 400 600 800
RelativeCorn Yield
withoutSidedress N
(fraction)
0.0
0.2
0.4
0.6
0.8
1.0
r2 = 0.64n = 43
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Flush of CO2 (mg CO2-C . kg-1 soil)0-3 d
0 200 400 600 800
Sidedress NitrogenRequired to Achieve
Optimum Corn Grain Yield(lb N/bu grain)
0.0
0.2
0.4
0.6
0.8
1.0 NR = 1.05 - 0.0015 * Flushr2 = 0.29
n = 36
Adjustment of N per bushel of grain…
Total of 36 fields in NC + VA
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Flush of CO2 (mg CO2-C . kg-1 soil)0-3 d
0 200 400 600 800
Sidedress NitrogenRequired to Achieve
Optimum Corn Silage Yield(lb N/ton silage)
0
2
4
6
8
10N = 7.2 - 0.014 * Flush
r2 = 0.44n = 11
Total of 11 fields in VA
Adjustment of N per ton of silage…
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Preliminary analysis for recommendation domain
Soil-Test Biological Activity
Very Low
LowMedium
HighFlush of CO2 (mg CO2-C
. kg-1 soil)0-3 d
0 200 400 600 800
Sidedress NitrogenRequired to Achieve
Optimum Corn Grain Yield(lb N/bu grain)
0.0
0.2
0.4
0.6
0.8
1.0 NR = 1.05 - 0.0015 * Flushr2 = 0.29
n = 36
Very High
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Wheat grain evaluations in North Carolina- 5 sites in 2015, 4 sites in 2016, and 10 sites in 2017
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Location of wheat N trials
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Flush of CO2 following Rewetting of Dried Soil(mg CO2-C kg-1 soil)0-3 days
0 200 400 600 800
Relative WheatDry Matter Yield
withoutN fertilizer
compared with135 kg N ha-1
(fraction)
0.0
0.2
0.4
0.6
0.8
1.0
Relative Yield = 1.14 * e-0.0048 * Flush
r2 = 0.48
Wheat yield response in NC
Total of 9 fields in western NC
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Autumn stockpiling of tall fescue- 19 sites in 2015 and 35 sites in 2016
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Location oftall fescue N trials
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Flush of CO2 following Rewetting of Dried Soil(mg CO2-C
. kg-1 soil)0-3 d
0 200 400 600 800
Net NitrogenMineralization
(mg . kg-1 soil)0-24 d
0
50
100
150
200
250NMIN = -23 + 0.40 * Flushr2 = 0.77
Flush of CO2 following Rewetting of Dried Soil(mg CO2-C
. kg-1 soil)0-3 d
0 200 400 600 800
Net NitrogenMineralization
(mg . kg-1 soil)0-24 d
0
50
100
150
200
250NMIN = -23 + 0.40 * Flushr2 = 0.77
Tall fescue nitrogen trials
Pehim-Limbu et al. (unpublished data)
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Asssssssss ss ssssssss ssssssssssss ss ssss ssssssssss
Pehim-Limbu et al. (unpublished data)
Nitrogen Fertilizer Rate (kg N . ha-1)0 50 100 150
ForageDry Matter
Yield@ 15% moisture
(kg . ha-1)
0
1000
2000
3000
An example from site near Butner NC
Tall fescue nitrogen trials
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Cost-return scenarios
Condition
Thresholdreturn
needed(lb forage/lb N)
Low N ($0.50/lb N) and high hay ($200/ton) 5
Low N ($0.50/lb N) and low hay ($100/ton) 10High N ($1.00/lb N) and high hay ($200/ton) 10
High N ($1.00/lb N) and low hay ($100/ton) 20
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Soil-Test Biological Activity(mg CO2-C
. kg-1 soil)0-3 d
0 200 400 600 800
Tall FescueYield Response
to Initial Dose of N(kg DM . kg-1 N)
0
10
20
30
r2 = 0.80
Tall fescue nitrogen trials
Pehim-Limbu et al. (unpublished data)
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Soil-Test Biological Activity(mg CO2-C
. kg-1 soil)0-3 d
0 200 400 600 800
Tall FescueYield Response
to Initial Dose of N(kg DM . kg-1 N)
0
10
20
30
40Composite analysis of 19 sites in 2015/16
Mean + standard deviation at each siteStrenth of fit of means (r2 = 0.80)
Coefficient of variationFlush of CO2 = 12 + 8%Yield response = 106 + 44%
Tall fescue nitrogen trials
Pehim-Limbu et al. (unpublished data)
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Flush of CO2 following Rewetting of Dried Soil(mg CO2-C
. kg-1 soil)0-3 d
0 200 400 600 800
Nitrogen Rateto Achieve
Optimum Yield(kg N . ha-1)
0
30
60
90
120
150
NR = 10 + 502 * e(-0.0159 * Flush)
r2 = 0.26, n = 80
Tall fescue nitrogen trials
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Tall fescue nitrogen trials
Soil-test biological activity
(mg CO2-C kg-1 soil 3 d-1)
Nitrogen fertilizer to achieve optimum yield
(lb N/a)
<200 55 + 45200-400 8 + 18
>400 13 + 30
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Available Nitrogen (kg ha-1)
RelativeYield
(fraction)
0.0
0.2
0.4
0.6
0.8
1.0Sites with high N
availability and low N fertilizer response
Goal of enlarging the biologically active N pool without causing
N leakage
Flush of CO2 (mg . kg-1 soil)0-3 d
Sites with low N availability and high N fertilizer response
The flush of CO2 as a predictive soil test
Farm profit
Environmental impact
A working hypothesis…
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Incubating soil in sealed jar with alkali to absorb CO2
Components
o 1-L canning jar with lid
o Two 60-mL graduated bottles with 50 g soil wetted to 50% WFPS (***)
o One 30-mL screw-cap vial containing 10 mL of 1 M NaOH to absorb CO2
o One 25-mL vial containing 10 mL water to maintain humidity
*** One bottle pre-incubated for 10 days prior to CHCl3
fumigation to estimate soil microbial biomass C
One bottle incubated for 24 days to determine cumulative C and N mineralization
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Soil biological activity is a key indicator for productivity and environmental quality
The flush of CO2 possesses many qualities of a robust soil test Rapid Inexpensive Reproducible Suitable for a wide range of soils Correlating to nutrient needs of crops