硝化抑制剂对黑土氮素转化的调控作用与机制

The application of nitrification inhibitor is an important measure to reduce nitrogen losses and to improve fertilizer use efficiency. In the past, most of the research on the inhibitors has been focused on the effect of nitrification inhibitors on fertilizer nitrogen transformation processes, the effect of inhibitors on soil nitrogen transformations have not been reported systematically, which limits the in-depth understanding of the mechanism of inhibitors. In this study, black soil, collected from the northeast part of China, will be used and nitrification inhibition and regulation of nitrogen transformation will be correlated to determine the effects of nitrification inhibitors on soil nitrogen mineralization and immobilization processes by isotopic differentiation of fertilizer nitrogen and soil original nitrogen. The effect of inhibitors on soil gross nitrogen transformation rates and nitrification rates will be analyzed by using 15N isotopic pool dilution to understanding the effects of inhibitors on organic nitrogen mineralization processes and nitrification processes. The effect of inhibitors on soil and fertilizer nitrogen immobilization process, net mineralization process and its relative contribution to N2O emissions will be determined by using 15N isotope tracer technology. Based on the dynamic equilibrium process relationship between nitrogen mineralization and mobilization, the mechanisms of inhibitor effects on soil nitrogen transformation process will be clarified. The effect of inhibitors on N2O emissions will also be evaluated. These results will provide a scientific basis for the rational application of nitrogen fertilizer.

硝化抑制剂的应用是减少农田氮素损失、提高肥料利用率的重要措施。以往的研究主要关注抑制剂对肥料氮素硝化过程的抑制作用，而其对土壤氮素转化过程的调控作用未得到重视，限制了对抑制剂作用机理的深入了解。因此，本项目以东北黑土为研究对象，将硝化抑制作用和氮素转化调控相结合，通过同位素区分肥料氮素和土壤原有氮素，对土壤氮素矿化和同化这两个相互关联的过程的动态变化和关联关系开展系统研究。通过15N库稀释法，研究抑制剂添加对作物生育期内土壤氮总矿化速率和硝化速率动态变化的影响，明晰土壤氮素矿化和硝化过程对硝化抑制剂添加的响应；利用15N肥料示踪技术，分析添加抑制剂条件下土壤原有氮素和肥料氮素微生物同化过程和净矿化速率的动态变化及N2O排放特征。通过分析土壤氮素矿化和微生物同化的动态平衡过程关系，阐明硝化抑制剂对土壤氮素转化过程的调控机理，并以N2O排放特征来评价调控作用效果，为氮肥的合理应用提供理论依据。

硝化抑制剂的施用被认为是提高农田氮素利用率的重要生化调控措施，但对土壤氮素转化过程影响方面的研究较少。因此，本项目以我国东北地区黑土为研究对象，选取硝化抑制剂DMPP，采用15N同位素稀释-原位培养法和稳定同位素分析技术，探讨施用硝化抑制剂后，肥料和土壤氮素在各氮库的分配和平衡过程及N2O排放特征。研究结果显示，抑制剂主要通过减少肥料氮素的损失而起到减排的作用。在玉米苗期，抑制剂显著提高了0-20cm土层肥料来源矿质氮的累积，氮总矿化速率和硝化速率分别减少8.81%和18.02%。从苗期到抽雄期期间，抑制剂促进了0-20cm土层肥料来源有机氮的快速释放过程，为作物生长提供充足的氮源，硝化抑制剂使氮肥更多地以NH4+的形式保持在土壤中，减少了NO3-的积累，这也是减少N2O排放的主要原因。在成熟期，0-60cm土层残留肥料氮、作物吸收肥料氮以及肥料氮的气态损失占所施入肥料的比例分别为29%、65%和16%，抑制剂使肥料氮的利用率提高了23%，其气态损失率降低了47%。说明抑制剂通过调控肥料氮在土壤不同形态氮库的转化过程，有效保障了土壤保氮以及供氮与作物需氮之间的同步性，有利于稳产增产、提高氮肥的利用效率，同时减少肥料氮损失带来的环境问题。