Management of nitrogen (N) fertilizer is critical to avoid the environmental consequences of both over-fertilization and excess reactive N in the system, and chronic under-fertilization and soil mining. Split N application seeks to improve nitrogen use efficiency in both small-holdings and large-scale mechanized farms, but lack of conclusive evidence on its benefits restricts the adoption of this practice. Here we report a global meta-analysis of split N application in wheat using 129 studies with 2661 comparisons. Split N in 3–4 applications improved yield by 7.0 % and grain protein by 5.2 % in relation to single application. The effect of split N on yield was larger for winter wheat than for spring wheat, while split N improved grain protein in both winter and spring wheat. Its effects on both yield and grain protein were larger under conventional tillage, in humid climate especially for winter wheat, in coarse textured soils, on less fertile soils, and at high N rate. Splitting N in 3–4 applications would increase annual production of winter wheat by 12.9 M t grain and 1.3 M t protein globally. By identifying the conditions where split N application is more likely to deliver agronomic benefits, our study would contribute to the targeted adoption of this practice.

氮 (N) 肥料的管理对于避免系统中过度施肥和过量活性氮以及长期施肥不足和土壤开采造成的环境后果至关重要。Split N 应用旨在提高小型农场和大型机械化农场的氮使用效率，但缺乏关于其益处的确凿证据限制了这种做法的采用。在这里，我们使用 129 项研究和 2661 项比较报告了对小麦中分离氮应用的全球荟萃分析。与单次施用相比，分次施用 3-4 次氮肥使产量提高了 7.0%，谷物蛋白质提高了 5.2%。冬小麦施氮肥对产量的影响大于春小麦，而施氮肥对冬小麦和春小麦的籽粒蛋白质均有改善作用。在常规耕作、潮湿气候（尤其是冬小麦）、质地粗糙的土壤、不太肥沃的土壤和高氮肥下，其对产量和谷物蛋白质的影响更大。在 3-4 次应用中分解氮将使全球冬小麦的年产量增加 12.9 M t 谷物和 1.3 M t 蛋白质。通过确定施氮肥更有可能带来农艺效益的条件，我们的研究将有助于有针对性地采用这种做法。