The aim of this study was to compare the effects of cowpea green manure and inorganic nitrogen (N) fertilizers on yields of winter wheat and soil emissions of nitrous oxide (N2O). The comparisons included cowpea grown solely as green manure where all biomass was terminated at maturity by tillage, summer fallow treatments with 90 kg N ha−1 as urea (90-N), and no fertilization (control) at planting of winter wheat. Fluxes of N2O were measured by closed chamber methods after soil incorporation of cowpea in autumn (October–November) and harvesting of winter wheat in summer (June–August). Growth and yields of winter wheat and N concentrations in grain and straw were also measured. Cowpea produced 9.5 Mg ha−1 shoot biomass with 253 kg N ha−1 at termination. Although soil moisture was favorable for denitrification after soil incorporation of cowpea biomass, low concentrations of soil mineral N restricted emissions of N2O from cowpea treatment. However, increased concentrations of soil mineral N and large rainfall-induced emissions were recorded from the cowpea treatment during summer. Growth of winter wheat, yield, and grain N concentrations were lowest in response to cowpea treatment and highest in 90-N treatment. In conclusion, late terminated cowpea may reduce yield of winter wheat and increase emissions of N2O outside of wheat growing seasons due to poor synchronization of N mineralization from cowpea biomass with N-demand of winter wheat.

中文翻译：

---

以豇豆为基础的绿肥和施氮肥对冬小麦产量和一氧化二氮排放的响应

本研究的目的是比较豇豆绿肥和无机氮 (N) 肥料对冬小麦产量和土壤一氧化二氮 (N) 排放的影响。2○）。比较包括仅作为绿肥种植的豇豆，其中所有生物量在成熟时通过耕作终止，夏季休耕处理 90 kg N ha-1如尿素（90-N），冬小麦种植时不施肥（对照）。N的通量2在秋季（10 月至 11 月）土壤掺入豇豆和夏季（6 月至 8 月）收获冬小麦后，通过密闭室方法测量 O。还测量了冬小麦的生长和产量以及谷物和稻草中的氮浓度。豇豆产量 9.5 毫克公顷-1枝条生物量 253 kg N ha-1在终止时。尽管土壤水分在掺入豇豆生物质后有利于反硝化，但土壤矿物质 N 的低浓度限制了 N 的排放2O 来自豇豆处理。然而，夏季豇豆处理记录了土壤矿物质氮浓度的增加和大量降雨引起的排放。冬小麦的生长、产量和籽粒氮浓度在豇豆处理中最低，在 90-N 处理中最高。总之，晚终止豇豆可能会降低冬小麦的产量并增加氮的排放2由于豇豆生物量中的氮矿化与冬小麦的氮需求同步性较差，导致小麦生长季节之外的 O。