Challenges & Opportunities For Mitigating N2O Emissions In Cropping Systems Of The Upper Midwest U.S.

Nitrous oxide (N2O) is often the dominant greenhouse gas (GHG) in agricultural production systems, and will continue to be important for the foreseeable future due to its strong ozone-depleting as well as global warming potential.   Emissions of N2O from cropping systems are also highly sensitive to soil water dynamics and temperature, and therefore the response of N2O to variable weather and changing climate is not easily predicted or managed.  Using data from our own and other studies, we discuss how traditional N management strategies designed to improve overall N use efficiency (e.g. modification of timing, source, or placement) do not always reduce N2O emissions, and how the challenges of reducing N2O emissions are often related to variable and/or extreme weather conditions.  For example, use of split applications, specialty fertilizer products, or improved placement do not always reduce, and in comes cases can actually increase, N2O emissions.   We also present recent data demonstrating the importance of nitrite dynamics, measured separately from nitrate dynamics, for improved insight and more effective mitigation of N2O emissions.  Additional findings are discussed which suggest N2O mitigation approaches that may be more robust to climate and weather effects and provide some directions for further study.