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

为了确定加拿大草原农业景观长期管理的最佳战略，我们需要提高我们对N循环过程和控制这些过程的因素的理解。拟议的研究计划将审查土地管理做法与具有农业和环境意义的氮循环过程之间的关系。重点将放在那些产生无机氮的过程(即矿化和硝化)和那些排放一氧化二氮的过程(即反硝化和硝化)。一氧化二氮是一种温室气体，其全球变暖潜力是二氧化碳的300倍，在加拿大，农业占人类排放的一氧化二氮的高达70%。特别需要更好地了解总氮生产过程，它指的是在特定时间段内有机氮库产生的无机氮总量，以及这些与氮排放过程的关系。到目前为止，很少有研究考虑景观尺度上的总氮生产，也没有人知道在加拿大草原上有这样的研究。为了解决氮循环知识方面的这一差距，拟议的研究计划将比较萨斯喀彻温省棕色、暗棕色和黑土区耕作和非耕作土地使用情况下的氮素生产和一氧化二氮排放。稳定的15N同位素技术将被用来(1)量化管理对旱作农田总矿化和硝化速率的影响，(2)估计硝化和反硝化对一氧化二氮排放的相对重要性。

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.