Strategies to mitigate nitrous oxide emissions from land applied manure

Nitrous oxide is an important greenhouse gas primarily produced by microbial nitrification and denitrification processes in soil. Emissions of N2O also occur indirectly when N is lost through NH3 volatilization or nitrate leaching and subsequently converted to N2O in another location. Direct and indirect N2O emissions represent an unproductive N loss from agricultural systems and therefore reducing emissions has benefits for greenhouse gas mitigation and improving N use efficiency. This paper reviews strategies for mitigating direct and indirect emissions of N2O from land applied manure. The discussion focuses on cattle and pig manure and includes strategies such as dietary measures, manure treatment, manure application timing, method and rate, tillage, cover crops and nitrification inhibitors. Finally, to illustrate the extent of mitigation potential, two mitigation options (i.e., shifting autumn manure application to spring and incorporating all manure within one day of application) were applied to the swine sector in Ontario, Canada. Emissions calculated for the baseline scenario and mitigation scenarios were compared. Results suggest that if both mitigation strategies were adopted, N2O emissions from field applied manure could be reduced by 17%. It is clear that opportunity for mitigation exists, but further research is needed to reduce uncertainty about the efficacy of mitigation options and barriers to on farm adoption. aper is part of the special issue entitled: Greenhouse Gases in Animal Agriculture – Finding a Balance between Food and Emissions, Guest Edited by T.A. McAllister, Section Guest Editors: K.A. Beauchemin, X. Hao, S. McGinn and Editor for Animal Feed Science and Technology, P.H. Robinson.