Development of Greenhouse Neutral Cropping Systems: Soil N2O Emissions from N Fertilizer Management and Organic Production Systems

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Despite recent emission reductions of greenhouse gases by most economic sectors in Canada, agriculture is lagging. This is because doubling in synthetic N fertilizer use has increased emissions of the greenhouse gas, nitrous oxide (N2O). Lowering emissions from N fertilizer use is imperative if we are to develop agricultural systems that are net non-emitters of greenhouse gases. Organic food production systems are thought to decrease net GHG emissions compared to conventional systems; however, reliable net GHG emission and life-cycle analysis of these systems is hindered by lack of understanding of their emissions of N2O. As part of the journey of the Soil Ecology Laboratory toward its long-term goal of changing how food is produced to be a net non-emitter of GHGs from soil, this Discovery Grant program focuses on N2O emissions and six attainable short-term goals; a) limiting emissions from the practice that many growers use in Western Canada to apply N fertilizer in fall by delaying the addition to just prior to freeze-up so emissions the following year are less, b) use newly available enhanced efficiency fertilizers to further reduce N transformations of fall-applied N to reduce early spring emissions, c) address the poor understanding of the magnitude of soil N2O emissions from organic production systems, d) develop an understanding of the contribution of the common practice of plough down of annual legumes in organically managed systems to N2O emissions, e) develop the most comprehensive net GHG analysis for an organic production system study, and f) overcome the limitation in application of a process-based model as a tool to estimate N2O emissions for the practices examined in this DG. The outcomes of this program are the development of N management practices to decrease N2O emissions from fertilizer use and understand the contribution of N2O emissions to greenhouse gas emissions from organic food production systems. The implications are a likely reversal in the recent trend for increasing N2O emissions from fertilizer use in Canada and elsewhere, as well as a more science-based promotion of the environmental benefit of organic production systems.