东北黑土玉米带土壤N2O和N2释放及其对秸秆还田和硝化抑制剂的响应

The Northeast China is one of the main production bases of corn in China, where nitrogen (N) fertilization is the basis for high yield of corn. With the increasing application of N fertilizer, as well as the development of approaches to "improving N utilization, reducing N loss", people are increasingly concerned about the gaseous loss of the fertilizer N applied into the fields, and its response to corresponding nutrient management actions. Due to the limited precipitation, the leaching and runoff losses of fertilizer N in Northeast China is less, and the gaseous N emissions may be the main pathway of total N loss. But until now, the quantity and biological mechanism of gaseous N emissions were still poorly understood. Restricted by the high costs of 15N-labelled fertilizer and the difficulties in detecting N2 emitted from soil, the N balance method and acetylene inhibition method with high uncertainties were usually used to quantify the gaseous N losses from soil. To this end, using in situ injection of 15N isotopic trace (high abundance), as well as high sensitive detection technology of 15N in N2 pool (low abundance), we plan to systematically study the gaseous N losses of fertilizer N as N2O and N2 (fluxes and proportions) in normal field condition, and in nutrient management condition (straw / nitrification inhibitor incorporation) in typical corn fields in Northeast China. In addition, combining field and lab-based soil incubation experiments, we also plan to explore the influence factors and the possible microbial mechanism affecting the release of N2O and N2 from soil. The results of this program, will deepen the understanding of related process and mechanism of N2O and N2 emissions from cropland soil in Northeast China, and will also provide insights into sustainable N management in the study region.

东北是我国玉米的主产地之一，氮肥施用是保证玉米高产的基础。随着氮肥施用量的增加以及相关“减氮增效”措施的应用推广，人们越来越关注施入该区域玉米系统肥料氮的利用和损失情况，及其对有关措施的响应。由于东北年降雨少氮流失有限，肥料氮则主要以气态途径损失，但目前我们对气态氮损失的形态数量和生物学机制还知之甚少。受标记成本和N2测定的限制，过去在量化气态氮损失时大多采用平衡法或乙炔抑制法，结果存在很大的不确定性。为此，本研究拟以东北典型的黑土玉米带土壤为研究对象，运用原位高丰度15N标记并结合室内灵敏的氮气15N丰度检测技术，系统研究在常规推荐施氮和不同农田养分管理（秸秆还田、硝化抑制剂施用）条件下土壤释放N2O和N2的速率比例，并揭示其影响因素和可能微生物机理。本项目研究的结果，在理论上将加深对旱地农田土壤气态氮损失关键过程的理解，在实践上也可为合理评价相关措施在玉米生产中的资源环境效应提供依据。

玉米是我国东北和华北区域种植范围最广的农作物。氮肥施用对于保证该区域玉米高产，维护国家粮食安全意义重大。但长期大量施肥以及不合理的田间管理，导致该区域玉米地土壤对氮素的调控能力不断衰退，氮素损失逐年增加，污染周边环境并影响全球变化。但是目前有关该区域（尤其是东北）玉米地土壤氮循环的研究仍然较少，对玉米生产过程中氮素的气态损失情况也不甚清楚。秸秆还田和硝化抑制剂施用被认为是提高农田养分利用率的重要调控措施，随着该区域环境问题的不断突出，研究了解常规施氮和养分管理条件下肥料氮的利用和损失效率就变得越来越迫切。本项目通过对旱地农田玉米土壤释放N2O和N2的潜力和规律的研究，系统分析了东北和华北区域土壤在不同条件下释放这两种气体的差异，研究了不同微生物途径和不同环境因子的贡献和影响，并探讨了其对施肥、硝化抑制剂添加和秸秆添加的响应。结果发现：1）好氧条件下，东北黑土N2O和N2的排放显著低于华北褐土（相差13-26倍）；厌氧条件下，两种土壤排放这两种气体的差异缩小；好氧条件下，N2O释放的相对比例的N2O/(N2O+N2)为4-68%，厌氧条件下的比例为2-32%；2）不管是好氧还是厌氧条件，土壤pH和有机质含量是影响气态氮损失的重要环境因子；3）秸秆和抑制剂施用显著减少了N2O和N2的排放，尤其以抑制剂在褐土中的效果更为显著（减少N2O和N2排放达67%和86%）；4）田间试验结果发现，氮肥穴施后，东北春玉米生长季土壤排放的N2O为1.4 kg N ha-1，约占氮肥当季氮肥的0.7%，其中来自氮肥的比例为30%，说明非当季肥料氮对N2O的贡献较大，这主要是由于肥料氮进入土壤后与土壤氮存在较大的交互作用。因此，采用短期15N示踪试验估算N2O排放因子将可能存在低估。目前已在Global Change Biology，Soil and Tillage Research等生态环境与土壤类期刊上发表论文2篇，其中第一作者SCI收录2篇，申报专利2项。本项目的研究成果加深了对旱地农田土壤N2O和N2损失关键过程和调控因子的理解，为硝化抑制剂和秸秆还田在田间的应用提供了依据。

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