冬小麦-夏花生种植系统生物固氮效应及氮素优化利用研究

The proper utilization of the biological N fixation of legume crop to decrease the N inputs of the cropping system, which is the critical path to carry out the high N use efficiency of the system. Winter wheat-summer peanut system is one of the most important cropping patterns in North China Plain, ascertaining the impacts of different N treatments on the biological N fixation of peanut and the influencing mechanism of the translocation of N from peanut on the N use efficiency of the following winter wheat are very important to decrease the nitrogen inputs and increase the N use efficiency in the winter wheat-summer peanut system. The winter wheat-summer peanut cropping system is the research object of the study, both field plot trails and microplot experiments are designed for the current study, the 15N isotope-dilution technique is adopted in the study. The measurements of the weight and the activity of peanut nodules at different at growth stages, and the measurements of total nitrogen content and 15N content in the whole plant of both summer peanut and winter wheat, and in soil depth until 200cm, are both conducted in order to obtain the nitrogen fixation effect of peanuts under different nitrogen application levels and therefore reveal the influencing mechanism of the translocation of N from peanut on the N use efficiency of the following winter wheat. At the same time, using STICS model to further analyze the effects of different nitrogen applications on the nitrogen utilization in the winter wheat-summer peanut system, and put forward the optimized nitrogen management mode under different yields target.

合理利用豆科生物固氮减少农田氮素肥料投入，是实现作物生产系统氮素高效利用的重要途径。冬小麦-夏花生是华北地区重要种植模式，阐明不同施氮水平花生固氮潜力、氮素转移及其对冬小麦氮素利用的影响机制，对冬小麦-夏花生系统氮肥节约高效利用意义重大。本研究以冬小麦-夏花生系统为研究对象，综合运用微区试验和小区试验，采用15N同位素标记技术，测定花生不同时期根瘤活性和根瘤重、夏花生和冬小麦收获期全株和0~200cm土体全氮含量和15N含量，研究不同施氮水平下花生固氮效应，揭示花生氮素转移对下茬冬小麦氮素利用的影响机制。同时，利用STICS模型进一步解析不同施氮水平对冬小麦-夏花生系统氮素利用的影响，提出不同目标产量下氮素优化管理模式。

冬小麦-夏花生是华北地区重要种植模式，氮肥过量投入显著影响了花生的固氮效率，导致系统的增产效益和氮素利用效率明显下降。合理利用豆科固氮减少系统氮肥投入，是提升系统氮素利用效率的关键途径。本项目基于3年田间定位试验和盆栽试验，结合STICS作物模型，重点开展了1）不同施氮水平对花生固氮效应的影响，2）花生氮素转移对下茬冬小麦氮素高效利用的影响，3）冬小麦-夏花生系统氮素优化管理等三方面的研究工作。研究结果表明：（1）过量施氮显著制约夏花生固氮效率，随着施氮量增加0-60cm土层NO3-含量升高，花生固氮酶活性下降，3年试验结果表明N0、N50、N100、N150和N200处理下夏花生的平均固氮量分别为95、79、70、45和40 kg N hm-2。（2）过量施氮使得夏花生贪青旺长，收获期籽粒灌浆不足导致产量降低，3年田间试验结果表明N150处理下夏花生单产水平最高。综合考虑经济收益、花生单产水平和氮肥利用效率，夏花生高产高效的适宜施肥区间为144-159 kg N hm-2。（3）花生季对下茬冬小麦存在明显的氮素转移现象；花生秸秆还田和根际沉降氮对下茬冬小麦的氮素贡献受花生季施氮量的影响，两年试验结果表明，不同夏花生施氮量对下茬冬小麦生长发育及其氮素吸收与显著影响，小麦产量随上茬夏花生土壤残留增加而增加，周年施氮量270 kg N hm-2是本研究中系统产量和氮素资源利用效率兼顾的施氮处理。（4）研究结果阐明了不同施氮水平对夏花生生物固氮效应的影响，揭示了不同施氮处理下夏花生对下茬冬小麦氮素转移特性，初步明确了华北地区冬小麦-夏花生系统高产高效的周年推荐施氮量，对优化不同目标产量下华北地区冬小麦-夏花生系统氮素优化管理具有重要意义。