Gross nitrogen cycling processes and nitrous oxide emissions in cultivated and non-cultivated hummocky soil landscapes

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To determine the best strategy for long-term management of agricultural landscapes in the Canadian Prairies, we need to improve our understanding of N-cycling processes and those factors controlling them. The proposed research program will examine the relationship between land management practices and N-cycling processes of agricultural and environmental significance. The emphasis will be on those processes that produce inorganic N (i.e., mineralization and nitrification) and those that emit nitrous oxide (i.e., denitrification and nitrification). Nitrous oxide is a greenhouse gas that has 300 times the global warming potential of carbon dioxide and in Canada, agriculture accounts for up to 70% of human-induced nitrous oxide emissions. There is particular need for improved understanding of gross N-producing processes, which refers to the total amount of inorganic N produced from the organic N pool in a given time period, and how these relate to N-emitting processes. To date there have been few studies considering gross N production at the landscape scale and none known of in the Canadian Prairies. To address this gap in N-cycling knowledge, the proposed research program will compare N production and nitrous oxide emissions under cultivated and non-cultivated land uses in the Brown, Dark Brown, and Black soil zones of Saskatchewan. Stable 15N isotope techniques will be used to (1) quantify management effects on gross mineralization and nitrification rates in hummocky till landscapes and (2) estimate the relative significance of nitrification and denitrification to nitrous oxide emissions.