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Agriculture, Carbon & the climateCO2 & climate change

Moberg et al. 2005

Source of C emissions

http://www.prism.gatech.edu/

• Change in temperature & rainfall• Extreme weather: drought, flood, storms• Food & resource insecurity

March 20, 2013

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Agriculture & the global C budget

CO2 mitigation via agriculture

• Agricultural land as a C sink• Reverse historic losses of SOC

• Immediately implementable• Cost-effective

Attractive mitigation option

• Cap & Trade – Chicago Climate Exchange (CCX)• Ecosystem service subsidies

Policy & rural economy

March 20, 2013

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How is carbon sequestered?• Photosynthesis - plants fix carbon from atmosphere (CO2) • Carbon that remains as plant tissue can be added to the soil as litter

or residue plants die and decompose• Stored in the soil is as soil organic matter (SOM)• SOM is a complex mixture of carbon compounds, consisting of

decomposing plant and animal tissue, microbes (protozoa, nematodes, fungi, and bacteria)

• Carbon can remain stored in soils for millennia, or be quickly released back into the atmosphere through respiration by soil microbes

• Climatic conditions, natural vegetation, soil texture, drainage, and human land use all affect the amount and length of time carbon is stored in soil.

March 20, 2013

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complexity

CornCorn

Soybean

Corn

SoyCloverGrain

Wheat

Corn

alfalfa

Alfalfa

AlfalfaAlfalfa

Oats/alfalfa

CornRotational

GrazingForage

WICST SOC trendsCropping systems

March 20, 2013

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Activity from Reading:

• From the top bubble on page 1624 – can you predict which of the WICST treatments might be more successful in sequestering carbon? Why?

March 20, 2013

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SOC trends at WICST

March 20, 2013

WICST SOC trends

Bars represent ±1 standard error; Pr>|t| , † p<0.1, * p<0.05, ** p<0.01

-20 -15 -10 -5 0 5 10 15 20

**0 to 15 cm15 to 30 cm30 to 60 cm60 to 90 cm

Δ SOC mass

Δ Mg ha-1

Gra

in sy

stem

sFo

rage

syst

ems

*

†

†

**

*

††

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8

Soil C inputs on WICSTARL (‘92-’09) LAC (‘92-’02)

System lbs C/acre-1

Cont. corn 5390 3301Min-till corn-sb 4081 3324Org grain (c-sb-w) 3038 2297Conv. Forage 6075 6353Organic Forage 6377 7145Pasture with managed grazing

5380 5548

eOrganic Webinar

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Group

System description

Estimated Annual C Inputc

Above Ground Below Ground Root / Shoot

------------ (kg ha-1) ------------

GrainCS1 continuous corn 3800 2240 0.58CS2 corn-soybean 2940 1670 0.56CS3 organic grain 2240 1200 0.54

Forage

CS4 conventional forage 3050 3840 1.25CS5 organic forage 3220 4010 1.24CS6 pasture 1590 4570 2.87

Soil C inputs on WICST

March 20, 2013

1840 1850 1860 1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 199020,000

30,000

40,000

50,000

60,000

70,000

80,000

90,000

Year

Simulated Field

Soi

l C,

kg

C/h

a

Simulated Simulated control

fertilized

manured

control fertilized

Field Field manured

Fallow year

Presented at Soil Carbon Sequestration Workshop, Kearney Foundation Soil Science, September 2003

©Applied GeoSolutions, LLC

Winter wheat field

150-Year Simulation for Soil C Dynamics in A Winter Wheat Field

with Different Cropping Practices at Rothamsted Station, UK

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WICST SOC trends

Δ g kg-1 Sign.NT vs. Tilled 2.8 †Forage vs. Grain 3.2 *

------ Estimated C inputs------Tillage Manure Aboveground Belowground

------------------------------------ r -------------------------------------0.10* 0.13** -0.05 0.11**

SOC (g kg-1) correlations

Pr>|t|, ns=not significant, † p<0.1, * p<0.05, ** p<0.01

General SOC (g kg-1) trends

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SOC decreases with tillage– NT: 2.8 g kg-1 > SOC than tilled– Negative correlation: tillage & SOC

Forage systems > grain systems– Forage: 3.2 g kg-1 > SOC than tilled– Positive correlation: manure & SOC

Pasture sequestered the most SOC– Sequestration only in pasture, but limited

WICST SOC trends

March 20, 2013

Presented at Soil Carbon Sequestration Workshop, Kearney Foundation Soil Science, September 2003

©Applied GeoSolutions, LLC

http://ngm.typepad.com/photos/uncategorized/2008/01/02/0103_os.jpg

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Relationship between N2O and Carbon

• Six et al. – N2O fluxes under NT higher than CT in drier environments – opposite trends in humid environments

• Other researchers have found opposite trends – Illustrate situation-specific nature of cropping

systems impacts on SOC storage and N2O emissions

– Show it is important to closely evaluate conditions under which conclusions are drawn

March 20, 2013

DNDC-modeled C sequestration, N2O emissions and their global warming potentials (GWP) for a corn-soybean rotation system with different tillage approaches in Adair County, Iowa from 1994-2014

Critical need for models to assess long-term impacts of management decisions!

C sequestration N2O flux SOC-GWP N2O-GWP Net GWP

kg C/ha/yr kg N/ha/yr kg CO2 equivalent/ha/yr

Intensive tillage

125 11.5 -459 5615 5156

Notill 468 21.1 -1716 10301 8585

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WICST LCA: Embedded Emissions

• Data from the GaBi databases– Seed – Diesel – Fertilizer– Pesticides – Grain Drying – Supplemental heifer feed while on pasture

• N2O, CH4, CO2 computed and converted to CO2 eq in kg/ha/yr

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Embedded components at ARL (kg CO2 eq/ha/yr), 1993-2008

1 2 3 4 5 6cont .corn NT c-sb org c-soy-wht green gold alf org c-oat/alf-alf pasture

grain dairy

0

200

400

600

800

1000

1200

1400

1600

1800

miscpesticmanurefertgraindrydieselkg

CO

2 eq

/ha/

yr

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RUSLE2 Soil loss estimates† (18-yr avg, ARL)

cont corn no-till c-sb org c-sb-w conv alfalfa org alfalfa pasture0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

Tons

/acr

e

† assuming 4% slope, 150 ft run, contours

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Conclusions & ImplicationsAgricultural

• NT, manure, forage crops – beneficial• Perennial grasses in crop rotations

– Grass ley• Perennial functionality

– Cover crops, intercropping

• Organic trends toward greater use of: manure, forage crops, perennial crops, cover cropping, and intercropping

• Overall reduction of tillage and inputs across systems is beneficial

March 20, 2013