Using Ecosystem Models to Inventory and Mitigate Environemntal Impacts of Agriculture 2006. Proceedings of Workshop on Agriculture Air Quality: State of the Science

Authors: Del Grosso, Stephen - Steve; PARTON, W - CSU, FORT COLLINS, CO; OJIMA, D - CSU, FORT COLLINS, CO; MOSIER, A - USDA-ARS, RETIRED

Submitted to: Proceedings of the Workshop on Agricultural Air Quality: State of the Science
Publication Type: Proceedings
Publication Acceptance Date: 3/9/2006
Publication Date: 6/5/2006
Citation: Del Grosso, S.J., Parton, W.J., Ojima, D.S., Mosier, A.R. 2006. Using Ecosystem Models to Inventory and Mitigate Environemntal Impacts of Agriculture 2006. Proceedings of Workshop on Agriculture Air Quality: State of the Science. Proceedings of the Workshop on Agricultural Air Quality: State of the Science. In V.P. Anaeja, W.H. Schlesinger, R. Knighton, G. Jennings, D. Niyogi, W. Gilliam, C.S. Duke (eds.) Proceedings Workshop on Agricultural Air Quality: State of the Science, p. 571-574. North Carolina State University, Department of Communication Services, Raleigh, NC, June 5-8, 2006.

Interpretive Summary: Agricultural soils are responsible for at least 50% of nitrous oxide (N2O) emissions and nitrate (NO3) leaching into waterways and a small but significant portion of NOx emissions in the USA. N2O is an important greenhouse gas (GHG) because it has a global warming potential ~300 times that of CO2 and contributes to the destruction of stratospheric ozone (O3). NO and NO2, together known as NOx, are precursors to surface level O3 and contribute to nutrient loading of aquatic and terrestrial ecosystems. NO3 is a primary contributor to eutrophication of lakes, rivers, and coastal waterways. N inputs, weather, soil type, and land management interact to control these N loss vectors. Process-based models that account for these interactions should yield more reliable estimates of these losses than simple empirical models. The process-based model DAYCENT has simulated N2O, NOx, and NO3 losses for agricultural soils in the USA at county level resolution for current land management practices. DAYCENT has also been used to compare different mitigation strategies. Simulations suggest that use of nitrification inhibitors and precision application of N fertilizers can decrease N gas losses and NO3 leaching while maintaining or increasing crop yields. Simulations also suggest that conversion to no till cultivation can sequester C in soil, but that in some systems, no till can lead to higher N gas and N leaching losses than conventional plowing. Therefore, the impacts of different land management practices on greenhouse gas fluxes and NOx emissions and NO3 leaching must all be considered when deciding overall best management strategies for different regions in the USA.

Technical Abstract: Agriculture is responsible for over 50% of global nitrous oxide (N2O) emissions and is also an important source of nitric oxide (NO) and nitrogen dioxide (NO2). N2O is an important greenhouse gas (GHG) because it has a global warming potential ~300 times that of CO2 and contributes to the destruction of stratospheric ozone (O3). NO and NO2, together known as NOx, are precursors to surface level O3 and contribute to nutrient loading of aquatic and terrestrial ecosystems. NOx is also considered an indirect source of N2O because after being emitted from agricultural soils it can be deposited on non-farm land, biochemically converted to N2O, and emitted to the atmosphere. Field data show that N oxide emissions are primarily a function of soil texture, water content, N additions, and land management. These relations have been quantified and implemented in N oxide emission models. Soil disturbance (e.g. plowing) tends to decrease the proportion of NOx compared to N2O emissions and analyses have shown that the majority of agricultural NOx emissions from agricultural soils in eastern Colorado are from rangeland as opposed to cropped soils. However, NOx emissions from energy production, transportation, and industry are higher than agricultural emissions for most counties in eastern Colorado. The authors have developed a methodology to assess N oxide emissions from agricultural soils using empirical and process based models. This methodology has been used for the US inventory of GHG’s and to evaluate different management strategies intended to mitigate environmental impacts of agriculture. US national maps of N oxide emissions from agricultural will be presented and the tradeoffs between N2O and NOx emissions and NO3 leaching into waterways will be explored.