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

为了确定加拿大大草原农业景观长期管理的最佳策略，我们需要提高对氮循环过程及其控制因素的理解。拟议的研究计划将研究土地管理实践与农业和环境意义上的氮循环过程之间的关系。重点将放在产生无机氮（即矿化和硝化）和排放氧化亚氮（即反硝化和硝化）的过程上。一氧化二氮是一种温室气体，其全球变暖潜能值是二氧化碳的300倍。在加拿大，农业排放的一氧化二氮占人为排放的70%。特别需要改进对总产氮过程的理解，这是指在给定时间段内从有机氮库中产生的无机氮的总量，以及这些与氮排放过程的关系。迄今为止，很少有研究在景观尺度上考虑总氮产量，而在加拿大大草原上则没有。为了解决在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、深棕色和黑色土壤区耕地和非耕地利用下的氮产量和一氧化二氮排放。稳定的15N同位素技术将用于(1)量化管理对丘陵区土壤总矿化和硝化速率的影响；(2)估计硝化和反硝化作用对氧化亚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.