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

尽管加拿大大多数经济部门最近都减少了温室气体的排放，但农业却落后了。这是因为合成氮肥的使用量增加了温室气体一氧化二氮（N2 O）的排放量。如果我们要发展温室气体净非排放的农业系统，减少氮肥使用的排放势在必行。与传统系统相比，有机食品生产系统被认为可以减少温室气体净排放量;然而，由于缺乏对这些系统的N2 O排放量的了解，这些系统的可靠的温室气体净排放量和生命周期分析受到阻碍。作为土壤生态学实验室实现其长期目标的一部分，即改变粮食生产方式，使其成为土壤中温室气体的净非排放者，该发现补助金计划侧重于N2 O排放和六个可实现的短期目标; a）通过将氮肥的添加时间推迟到冻结之前，限制加拿大西部许多种植者在秋季施用氮肥的做法所产生的排放; B）使用新的高效肥料，以进一步减少秋季施氮的氮转化，以减少早春排放，c）解决对有机生产系统土壤N2 O排放量的认识不足，（d）了解在有机管理系统中犁耕一年生豆类作物的常见做法对一氧化二氮排放的影响，e）为有机生产系统研究开发最全面的净温室气体分析，以及f）克服应用基于过程的模型作为估算本DG所研究实践的N2 O排放量的工具的局限性。该计划的成果是N管理实践的发展，以减少化肥使用的N2 O排放，并了解N2 O排放对有机食品生产系统温室气体排放的贡献。其影响可能是最近加拿大和其他地方使用化肥增加N2 O排放的趋势发生逆转，以及更科学地促进有机生产系统的环境效益。

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.