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2010 Annual Report

1a. Objectives (from AD-416)
To assist ARS in producing the U.S. Agriculture and Forestry Greenhouse Gas Inventory and assess the impacts of different crop management practices at the national scale. These efforts will facilitate collaborative efforts between ARS and CSU to continue simulation model development, testing, and refinement of input data to predict the impacts of changing climate and management on greenhouse gas (GHG) emissions, crop yields and soil carbon content.

1b. Approach (from AD-416)
Major products so far include the 2nd edition of the USDA GHG inventory published in 2008 and development of the GRACEnet data entry template. Major improvements in the 2nd edition of the inventory include more refined partitioning of GHG sinks and sources, better quantification of uncertainty and more accurate emission estimates, and quantification of mitigation potentials. Model improvements, tests, and applications used to generate data for the inventory have been reported in 12 journal and several presentations at meetings and symposia. The DAYCENT model was used to perform life cycle analysis for different biofuel cropping systems and initial tests were conducted to implement high resolution NRI data for future GHG inventory simulations. In addition to producing and improving future editions of the USDA GHG Inventory, general goals for the next 5 years include evaluating biofuel cropping systems and investigating how changes in land use and climate impact crop yields and GHG fluxes. Production and improvement of the U.S. Agriculture and Forestry Greenhouse Gas Inventory requires applying and improving the models used to calculate emissions and their associated uncertainty ranges. Use of more refined model input data, further comparison of model outputs with field measurements, and increased computing capacity lead to more accurate national scale estimates and better characterization of the regional and temporal patterns of emissions. ARS will interact with CSU to incorporate programming expertise, high capacity computing clusters, and data collection into the inventory analyses. CSU will assist ARS in evaluating the impacts and feasibility of different cropping systems, including biofuels by implementing and testing the ability of models to represent the impacts of improved N management technologies and perform regional analysis to identify local best management practices.

3. Progress Report
ARS and Colorado State University have incorporated programming and computer systems into GHG inventory and mitigation analyses. A rigorous methodology to quantify uncertainty in soil nitrous oxide emissions using the DayCent biogeochemical model was recently developed. This improved methodology resulted in more reliable emission estimates and are described in the 2010 EPA Inventory of U.S. Greenhouse Gas Emissions and Sinks and in a journal article (Del Grosso et al. 2010). The new methodology was also used to generate emissions estimates for the 3rd edition of the U.S. Agriculture and Forestry Greenhouse Gas Inventory to be published by USDA in 2010. The DayCent model has been shown to accurately represent biomass yields for biofuel cropping systems (Davis et al. 2010) and a manuscript describing regional simulations to assess the potential of biofuels to mitigate greenhouse gas emissions from the Mississippi basin is in preparation. These simulations suggest that converting land in the basin currently used for corn ethanol cropping to perennial biofuel crops could reduce greenhouse gas emission by approximately 40% while increasing ethanol yields by up to 80%. DayCent has also been run nationwide to quantify the impacts of various mitigation strategies in different region of the U.S. and a manuscript is in preparation describing the results of these simulations. ADODR monitoring was conducted via phone calls, e-mails, and on-site meetings.

4. Accomplishments