农作措施对中国稻田氧化亚氮排放影响的研究进展

农业是全球最主要的温室气体排放源之一,稻田不仅是全球重要的甲烷(CH4)排放源,亦是氧化亚氮(N2O)的重要排放源。灌溉、施肥、耕作等农作措施能够改变稻田生态系统土壤微环境,影响土壤硝化与反硝化过程,进而影响N2O的排放。目前,关于农作措施对农田生态系统N2O排放特征研究很多,但系统地综述农作措施对稻田N2O排放影响的研究还比较少。该文着眼于中国的农业发展趋势,基于稻田灌溉、施肥及耕作等方面的新技术,综合分析新型农作措施对中国稻田生态系统N2O排放的影响及其机制,为相关研究提供参考。在此基础上,提出了中国稻田生态系统N2O排放深入研究的方向:1)加强研究新型农作措施下稻田N2O产生及排放途径;2)系统研究稻田生态系统直接与间接N2O排放的影响及其机制;3)开展农作措施集成技术对稻田生态系统N2O排放影响的研究;4)加强模型模拟的调参验证并进行相关预测分析。

Review on management-induced nitrous oxide emissions from paddy ecosystems

Abstract: Climate change, as one of the most important environmental issues, has become an increasing global concern to scientists, policy makers, and the public. Paddy soils are a dominant source of N2O emissions. Agricultural management practices (e.g., water regime, fertilizers management, tillage) have important impacts on N2O emissions due to the changing microenvironment of paddy fields that can affect the processes of soil nitrification and denitrification. This paper summaried current literatures on the influence of these practices on N2O production and emission and their corresponding mechanisms in rice fields. At present, the generation and the pathway of N2O emission from paddy soils are clarified. Nevertheless, the current information on the action of farming management practices on N2O indirect emission is limited. The fertilizer application rate, the various types of fertilizers, and the varying timing and placement of application have a significant effect on the N2O emissions of paddy fields due to the different supplementation of nitrate and ammonium substrate in the processes of nitrification and denitrification. Generally, N2O emissions increase with increasing nitrogen (N) fertilizer rate. Previous studies showed that applying N fertilizer deeper can decrease N2O emissions compared to surface application. Water regime exerts substantial influence on N2O emission through the changes in oxidation and reduction in paddy soil layers during rice cropping. The mid-season aeration and drying-wetting alternation can stimulate N2O generation and emissions from paddy soils. Tillage and residue management practices can also affect nitrification and denitrification due to the change of soil characteristics. However, cultivation patterns do not have significant impacts on N2O emissions from paddy fields in current studies. Further research is needed to study the long-term effects of cultivations on N2O emissions. Most studies showed that N2O emissions decrease by incorporating biochar into paddy soils, but inconsistent results have also been reported. In addition, models (e.g., DNDC, CENTURY) are good options to simulate the effects of alternative agricultural practices on N2O emission from paddy fields and to identify potential strategies for climate change mitigation. In addition, the different effect of farming management practices on N2O emission may be presented based on the difference of many factors (e.g., climate conditions, soil types). An immense challenge to find ways to reduce N2O emission from paddy soils lies ahead for the scientific community and policy makers. Researchable priorities should be: 1) to implement exhaustive research on mechanisms that new agricultural management practices affect N2O generation and its emission pathways; 2) to assess effect of agricultural practices on the direct and indirect N2O emissions from paddy fields and their mechanisms; 3) to make in-depth studies on characteristics of N2O emission in technologies with integration of various farming practices; and 4) to simulate and forecast impacts of agricultural practices on N2O emissions in paddy ecosystems. Integrated farming approaches that exert a crucial role in the reduction of N2O emissions from paddy soils are necessary to be explored to mitigate the consequences of climate change on our planet.