Winter wheat (Triticum aestivum) is one of Switzerland’s most important field crops and requires large quantities of nitrogen (N) to produce a high yielding and high-quality crop. However, N is an expensive input for producers that is prone to environmental losses, thus causing pollution and environmental degradation. Furthermore, the N use efficiency (NUE) of wheat remains low. Our goals were to test whether different N fertilizer splits could maximize grain yield and grain N content (a proxy for grain quality) while improving nitrogen use efficiency, identify key variables in determining yield and N grain content, and to determine if variety- and site-specific fertilization recommendations provide additional benefits to nutrient use efficiency. We designed a four-year study across three sites in Switzerland that incorporated five top Swiss varieties of winter wheat and six different N application regimes applied at BBCH 21, 31, and/or 39 that totaled either 0, 80, or 160 kg N ha⁻¹. In addition to mixed model analyses, we used random forest to identify key genetic, environmental, and management variables in determining wheat grain yield and grain N content. Grain N content and yield were found to be maximized at 8000 kg ha⁻¹ and ≈ 2.24% N. Further, more N is required to increase grain N content compared to yield. With respect to nitrogen use efficiency, we found that the total amount of N applied has a greater effect on NUE compared to the rate of the N splits. In general, the rate of the first and second N applications were most important in determining both yield and grain N content, but the rate of the third N application was important in determining the latter. In general, our results did not show broad support for variety-specific fertilization, however site-specific fertilization holds some promise. Creating a winter wheat fertilization system that reduces negative environmental externalities while retaining high yields and quality remains challenging. However, we found that under the conditions tested here, a N regime of 40-40-80 kg N ha⁻¹ may maximize both yield and grain N content, and under some circumstances, improve nitrogen utilization efficiency. This may provide environmental benefits, as well as monetary benefits for producers. Given the current focus on nitrogen use and regulation, research maximizing the utility of nitrogen applications to ensure high grain yield, grain N content, and nitrogen use efficiency is vitally important. This and future work will help producers grow high-quality crops while lessening the environmental impact.

冬小麦 ( Triticum aestivum)是瑞士最重要的大田作物之一，需要大量的氮 (N) 才能生产出高产、优质的作物。然而，氮对于生产者来说是一种昂贵的投入，容易造成环境损失，从而造成污染和环境退化。此外，小麦的氮利用效率（NUE）仍然较低。我们的目标是测试不同的氮肥分配是否可以最大限度地提高谷物产量和谷物氮含量（谷物质量的代表），同时提高氮利用效率，确定确定产量和氮谷物含量的关键变量，并确定品种和地点是否可以-具体的施肥建议为养分利用效率提供了额外的好处。我们在瑞士的三个地点设计了一项为期四年的研究，其中纳入了瑞士五种顶级冬小麦品种以及在 BBCH 21、31 和/或 39 上应用的六种不同的氮肥施用方案，总氮肥施用量为 0、80 或 160 kg ha ⁻¹。除了混合模型分析之外，我们还使用随机森林来识别确定小麦籽粒产量和籽粒氮含量的关键遗传、环境和管理变量。^{发现谷物氮含量和产量在 8000 kg ha -1}和 ≈ 2.24% N时达到最大。此外，与产量相比，需要更多的氮来增加谷物氮含量。关于氮肥利用效率，我们发现施氮总量对NUE的影响比施氮量的影响更大。一般来说，第一次和第二次施氮量对于决定产量和籽粒氮含量最重要，但第三次施氮量对于确定后者很重要。总的来说，我们的结果并未显示出对品种特异性施肥的广泛支持，但地点特异性施肥具有一定的前景。创建一个减少负面环境外部性同时保持高产和优质的冬小麦施肥系统仍然具有挑战性。然而，我们发现，在此测试的条件下，40-40-80 kg N ha ^-1的氮肥制度可以最大限度地提高产量和籽粒氮含量，并且在某些情况下，提高氮肥利用效率。这可能会带来环境效益，并为生产者带来金钱利益。鉴于当前对氮肥利用和调控的关注，研究最大限度地利用氮肥应用以确保高谷物产量、谷物氮含量和氮肥利用效率至关重要。这项工作和未来的工作将帮助生产者种植高质量的作物，同时减少对环境的影响。