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

尽管最近加拿大的大多数经济部门都减少了温室气体的排放，但农业却落后了。这是因为合成氮肥使用量翻倍增加了温室气体一氧化二氮(N2O)的排放。如果我们要发展净不排放温室气体的农业系统，降低氮肥使用的排放量就势在必行。有机食品生产系统被认为与传统系统相比可以减少温室气体净排放量；然而，由于缺乏对其N2O排放的了解，这些系统可靠的温室气体净排放量和生命周期分析受到阻碍。作为土壤生态实验室迈向其长期目标的一部分，即改变粮食的生产方式，使其成为土壤温室气体的净非排放者，这项发现资助计划侧重于N2O排放和六个可实现的短期目标；A)限制加拿大西部许多种植者在秋季施用氮肥的做法的排放量，方法是在冻结之前推迟添加氮肥，以便第二年的排放量更少，b)使用新获得的提高效率的化肥，进一步减少秋季施用的氮素的转化，以减少早春的排放，c)解决对有机生产系统土壤N2O排放的严重程度的认识不足，d)了解有机管理系统中一年生豆类作物耕作对N2O排放的常见做法对N2O排放的贡献，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)克服在应用基于过程的模型作为估计本总干事所审查的做法的N2O排放量的工具方面的限制。该项目的成果是制定了氮管理实践，以减少化肥使用造成的N2O排放，并了解N2O排放对有机食品生产系统温室气体排放的贡献。这些影响可能会逆转加拿大和其他地方化肥使用导致的N2O排放增加的近期趋势，以及更多地以科学为基础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.