|Rotz, Clarence - Al|
Submitted to: Biogeochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/24/2012
Publication Date: 10/23/2012
Citation: Robertson, G.P., Bruulesema, T.W., Gehl, R., Kanter, D., Mauzerall, D., Rotz, C.A., Williams, C. 2012. Nitrogen – climate interactions in US agriculture. Biogeochemistry. DOI 10.1007/s10533-012-9802-4. Interpretive Summary: Nitrogen is an essential element for plant and animal growth, and our ability to harness nitrogen in its reactive forms has fundamentally transformed how we produce food. Fertilizers, manure, and legume fixation are the three main inputs of N to US agricultural soils. Nitrogen is lost from agricultural systems through atmospheric emissions and waterways leaching and runoff contribute to a number of types of environmental pollution. Fertilizer and pressures on producers for higher environmental performance are encouraging. Here we address the sources and fates of N in both cropping systems and animal agriculture and then assess some of the effects of climate change on the US agricultural N cycle as well as the effects of N use on climate. We then summarize a number of mitigation opportunities and current policy efforts before concluding with future research needs.
Technical Abstract: Agriculture in the United States cycles large quantities of nitrogen (N) to produce food, fuel and fiber and is a major source of excess reactive nitrogen (Nr) in the environment. Nitrogen lost from cropping systems and animal operations moves to waterways, groundwater, and the atmosphere. Changes in climate and climate variability may further affect the ability of agricultural systems to conserve N. The N that escapes affects climate directly through the emissions of nitrous oxide (N2O), and indirectly through the loss of nitrate, nitrogen oxides (NOx) and ammonia (NH3) to downstream and downwind ecosystems that then emit some of the N received as N2O and NOx. Emissions of NOx lead to the formation of tropospheric ozone, itself a greenhouse gas that can also directly harm crop productivity. There are many opportunities to mitigate the impact of agricultural N on climate and the impact of climate on agricultural N. Some are available today; many need further research; and all await effective incentives to become adopted. Research needs can be grouped into four major categories: (1) an improved understanding of agricultural N cycle responses to changing climate; (2) a systems-level understanding of important crop and animal systems sufficient to identify key interactions and feedbacks; (3) the further development and testing of quantitative models capable of predicting N-climate interactions with confidence across a wide variety of crop-soil-climate combinations; and (4) socioecological research to better understand the incentives necessary to achieve meaningful deployment of realistic solutions.