Abstract The objectives of this work were to determine the effects of initiating application of fertilizer nitrogen (N) to winter wheat at different growth stages (GSs) on grain yield and N use efficiency (NUE). A factorial experiment was carried out in two growing seasons (2011 and 2012) with five timings of first N application (GS 24/26 [tillering], GS 30, GS 31, GS 32 or GS 37) and an unfertilized control, two sowing densities (100 and 400 seeds/m2) and a cattle slurry treatment (with or without slurry). The latter was included to simulate variation in soil N supply (SNS). Delaying the first application of N from the tillering stage until GS 30 had no significant effect on grain yield in either year. Further delaying the initial N application until GS 31 caused a significant yield reduction in 2011, in comparison to GS 30 application, but not in 2012. Differences in efficiency of recovery and use of fertilizer N by the crop among the first three application timings were small. There was no evidence to support alteration in the timing of the first application of N in response to low plant density. Slurry application did not influence SNS, so the interaction between SNS and fertilizer N application timing could not be determined. It is concluded that in order to maximise yield and NUE, the first N application should be applied to winter wheat between late tillering and GS 30 and that delaying the first N until GS 31 can lead to yield reductions compared to the yield obtained with earlier application.

中文翻译：

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氮肥施用时机对爱尔兰冬小麦氮素利用效率和籽粒产量的影响

摘要 本工作的目的是确定在不同生育阶段（GSs）的冬小麦开始施氮肥（N）对谷物产量和氮素利用效率（NUE）的影响。在两个生长季节（2011 年和 2012 年）进行了一项因子试验，其中有五个首次施氮时间（GS 24/26 [分蘖]、GS 30、GS 31、GS 32 或 GS​​ 37）和未施肥对照，两次播种密度（100 和 400 粒种子/平方米）和牛泥浆处理（有或没有泥浆）。后者用于模拟土壤氮供应（SNS）的变化。从分蘖阶段推迟到 GS 30 的第一次施氮对任何一年的粮食产量都没有显着影响。与 GS 30 应用相比，进一步推迟初始施氮直到 GS 31 导致 2011 年产量显着下降，但在 2012 年并非如此。前三个施肥时期作物对氮肥的回收和利用效率差异很小。没有证据支持第一次施氮时间因植物密度低而改变。施肥对 SNS 没有影响，因此无法确定 SNS 与施氮时间之间的相互作用。得出的结论是，为了最大限度地提高产量和 NUE，应该在晚分蘖和 GS 30 之间对冬小麦进行第一次施氮，并且与较早施用获得的产量相比，将第一次施氮推迟到 GS 31 会导致产量降低. 没有证据支持第一次施氮时间因植物密度低而改变。施肥对 SNS 没有影响，因此无法确定 SNS 与施氮时机之间的相互作用。得出的结论是，为了最大限度地提高产量和 NUE，应该在晚分蘖和 GS 30 之间对冬小麦进行第一次施氮，并且与较早施用获得的产量相比，将第一次施氮推迟到 GS 31 会导致产量降低. 没有证据支持第一次施氮时间因植物密度低而改变。施肥对 SNS 没有影响，因此无法确定 SNS 与施氮时机之间的相互作用。得出的结论是，为了最大限度地提高产量和 NUE，应该在晚分蘖和 GS 30 之间对冬小麦进行第一次施氮，并且与较早施用获得的产量相比，将第一次施氮推迟到 GS 31 会导致产量降低.