1. Carbon Budget of Mature No-till Corn/Soybean Ecosystem in the North Central Region of the United States
Carl J. Bernacchi
Steven E. Hollinger
Illinois State Water Survey, Champaign, IL
Tilden P. Meyers
NOAA Atmospheric Turbulence Diffusion Division, Oak Ridge, Tennessee

2. Why Corn and Soybean?

3. Agricultural Land and C-sequestration
Soils of native prairie were high in Soil Organic Carbon (SOC)
Only ~40% of SOC still remains
Can we increase SOC in the soils of Midwestern agriculture?
Donigian, et al. (1994), U.S.EPA, Athens, GA
Lal, R., 2004, Science, 304,

4. Rising Atmospheric CO2
Controlling atmospheric CO2 is the focus of domestic and international efforts
Improvements in energy
More efficient technology
Improved fuels
Kyoto protocol
Sequester C
Sell C-credits

5. Focus on No-till No-till farming has many benefits Lower costs
Minimize erosion
Better soil moisture
More pest predators, earth worms
Higher SOC (?)

6. Measuring SOC
Soil measurements and models are traditionally used, but:
Soil measurements are prone to uncertainties over time and space
Models require validation
Augment the wealth of soil measurements / models with a different technique

7. Using Eddy Covariance to Estimate C Sequestration
Eddy Covariance is a method in which fluxes of CO2, water, and energy can be measured directly
Measurements represent a large area
Measurements are made continuously throughout the year

8. CO2 fluxes to measure NEE
Net Ecosystem Exchange = net total amount of C transferred between the atmosphere and an ecosystem over a given period of time
Pn = Net photosynthesis
Ra = Autotrophic Respiration
Rh = Heterotrophic Respiration

9. Bondville Ameriflux
Tower

10. Experimental Method 6 years of continuous eddy covariance measurements
Corn/soybean rotation agro-ecosystem
3 years of corn data
3 years of soybean data
3 complete rotation cycles
Data collected and back-filled (modeled) as needed

11. Carbon Sequestration Potential
If the amount of CO2 ENTERING the ecosystem is greater than the amount of CO2 LEAVING the system, then carbon is being sequestered

12. NEE over Six Years

13. Local C Fluxes
Carbon
Sink

14. Large C-Sink, however…
A large amount of C is removed from the field (yield)
100% of grain C is consumed annually
Does yield explain all of this sink?

15. How much C is removed from the no-tilled field?
Grain C

16. Regional C sink assessment
An Intensive Campaign (NACP) has been proposed to do the most comprehensive C budget ever for a certain region of the U.S.
Midwest defined as an ideal location
Relatively few urban areas
Single ecosystem type dominates
A Regional Intensive Campaign requires as much information as possible for each ecosystem type

17. Regional C Budget
Here in the Midwest, a large amount of C is fixed into grain
The grain is removed from the field
100% of grain harvest is utilized
Only ~20% of the total grain consumption occurs in the Midwest

18. Assessing the Regional C Budget
Have
Three years of NEE data for corn, soybean
Precise yield data for these years on the exact field
Yield data for each state in the U.S.
Grain consumption statistics
Need
NEE data for all states
Assumptions
Our field is representative of all fields

19. Ecosystem Harvest Index (EHI)
Grain carbon (Cgr) was measured via combine yield monitors
Growing season NEE (NEEg) was measured using eddy covariance
EHI was then used as a proxy for NEE over the whole Midwest

20. Midwestern Carbon Fluxes (MMT)
C Fluxes (MMT)
Maize
Soybean
Total
Growing season
-154.7
-59.3
-214
Fallow season
49.5
65.0
114.5
Midwest Consumption
13.9
4.3
18.2
Net Midwest
-91.3
10.0
-81.3

21. Regional C sink assessment

22. Conclusions
Locally, Midwestern corn/soybean ecosystem represents a large C-sink to the atmosphere
Globally, most of the C-sink is found in grain
Accounting for all Grain C, ecosystem is still a sink (C sequestration potential exists)

23. Conclusions (cont’) Regionally, a huge C sink exists
Most C stored in grain is consumed out of the region
Over 81 MMT of C is fixed in this region

24. Acknowledgements
Office of Science (BER), U.S. Department of Energy, Grant No DE-FG02-03ER63685
National Oceanic and Atmospheric Association (NOAA)
John Reifsteck