Nitrogen (N) losses from croplands substantially contribute to global N pollution. Assessing the reduction in N losses through improved N management practices is complex due to varying site conditions, such as land use, climate, soil properties and local farming methods. In this Article, we conducted a meta-analysis to evaluate the effects of improved practices on N loss reduction, analysing data from 1,065 studies with 6,753 pairs of observations comparing standard and optimized practices. Without considering site-specific conditions, optimized management practices can reduce N₂O emissions by 3–39%, NH₃ emissions by 15–68%, N run-off by 21–37% and N leaching by 19–52%. After considering local conditions and current practices, average reductions on a global scale were 31% for N₂O, 23% for NH₃, 18% for N run-off and 17% for N leaching. The effectiveness of N loss reduction was mainly influenced by optimized management practices and, to a lesser extent, site conditions. The results of this study underscore the importance of implementing optimized, site-specific management to effectively reduce N losses from global croplands.

农田的氮 （N） 损失是造成全球氮污染的重要原因。由于场地条件不同，例如土地利用、气候、土壤特性和当地耕作方法，评估通过改进氮管理实践减少的氮损失是复杂的。在本文中，我们进行了一项荟萃分析，以评估改进做法对减少氮损失的影响，分析了 1,065 项研究的数据，其中 6,753 对观察结果比较了标准实践和优化实践。在不考虑特定地点条件的情况下，优化的管理实践可以将 N₂O 排放减少 3-39%，NH₃ 排放减少 15-68%，氮径流减少 21-37%，氮浸出减少 19-52%。在考虑了当地条件和当前做法后，全球范围内 N₂O 的平均减少量为 31%，NH_{23 为 3}%，N 径流为 18%，N 浸出量为 17%。减少氮损失的有效性主要受优化管理实践的影响，在较小程度上受场地条件的影响。这项研究的结果强调了实施优化的、针对特定地点的管理以有效减少全球农田氮损失的重要性。