agriculture, carbon & the climate co 2 & climate change moberg et al. 2005 source of c...
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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
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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.
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complexity
CornCorn
Soybean
Corn
SoyCloverGrain
Wheat
Corn
alfalfa
Alfalfa
AlfalfaAlfalfa
Oats/alfalfa
CornRotational
GrazingForage
WICST SOC trendsCropping systems
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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?
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SOC trends at WICST
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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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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
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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
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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
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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