Optimized agricultural management reduces global cropland nitrogen losses to air and water

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. Increased agricultural nitrogen inputs lead to elevated nitrogen losses and may result in detrimental environmental impacts. This study uses meta-analyses to evaluate and predict changes in nitrogen losses to air and water in response to sustainable nutrient, crop and soil management practices.