Submitted to: American Society of Agronomy Abstracts
Publication Type: Proceedings
Publication Acceptance Date: 10/13/2006
Publication Date: 11/12/2006
Citation: Del Grosso, S.J., Follett, R.F., Wallace, J. 2006. Daycent model analysis of net greenhouse gas fluxes for farm fields in eastern virginia. American Society of Agronomy Abstracts on CD ROM. Interpretive Summary:
Technical Abstract: Growing high input crops, double cropping, and reducing or eliminating tillage have been shown to increase soil organic carbon (SOC) levels and these practices have been suggested as means to mitigate anthropogenic greenhouse gas (GHG) emissions. However, all 3 important biogenic GHG’s (CO2, N2O, CH4) must be considered to fairly evaluate the impacts of different land management strategies. Fluxes of all 3 gases are rarely measured in field plots due to practical and monetary constraints. But models that simulate the processes that control GHG fluxes can be readily used to compare how land management affects GHG’s and other variables such as NO3 leaching. The DAYCENT biogeochemical model was tested using crop yield and SOC data from 24 fields representing 3 soil series, different crop rotations, and different tillage intensities. Comparison of observed and simulated crop yields and SOC levels yielded r2 values of 0.74 and 0.61, respectively. DAYCENT was then used to project SOC changes, direct and indirect N2O emissions, CH4 uptake, and NO3 leaching from 2006-2020. Net GHG flux was calculated for 3 tillage alternatives: plow before all crops are planted, plow only before small grains are planted, and never plow. Model results suggest that as tillage intensity decreases, SOC sequestration increases substantially while N2O emissions, CH4 uptake, and NO3 leaching can increase or decrease by small amounts. After converting fluxes of all 3 gases to CO2-C equivalents and accounting for the CO2 emissions associated with production of nitrogen fertilizer, DAYCENT projected that these soils will remain net GHG sinks or neutral under no till until at least 2020 but emit significant amounts of GHG’s if they are regularly tilled.