Legume effects on N2O emissions do not compromise their role in sustainable agriculture: A global meta-analysis

Legumes are central to sustainable agriculture, improving soil quality, suppressing plant diseases, and boosting crop yields. They may also reduce soil nitrous oxide (N 2 O) emissions, a potent greenhouse gas, by reducing dependence on synthetic nitrogen fertilizers. However, biological nitrogen fixation by legumes provides easily decomposable nitrogen-rich residues, which may stimulate N 2 O production through nitrification and denitrification. As a result, the net impact of legumes on N 2 O emissions remains uncertain. To address this knowledge gap, we conducted a global meta-analysis of 1057 observations from 149 studies. We systematically compared N 2 O emissions between legume and non-legume cropping systems, including cover crops, rotations, intercropping, and monocultures. Averaged across the entire dataset, legumes did not significantly alter N 2 O emissions. However, in systems without N fertilization, legumes increased N 2 O emissions by 34.5–54%. Moreover, legumes increased cash crop yield by 17.2% in rotation and cover crop systems. Soil mineral nitrogen content was the most important driver of legume-induced N 2 O emissions ( R = 0.41, p < 0.05). We also identified environmental conditions under which legume-associated N 2 O emissions are elevated: cold annual temperatures (< 10 °C), high annual precipitation (> 800 mm), moderate soil bulk density (1–1.3 g cm −3 ), and low total soil nitrogen (< 0.5 g kg −1 ). Several management strategies could mitigate legume-induced emissions: minimizing tillage, using efficient irrigation systems, incorporating grain legumes into rotations or monocultures, reducing harvest frequency, reducing nitrogen fertilizers inputs to legumes, and managing legume residues through mulching or harvesting rather than incorporation. By clarifying the complex role of legumes in global N 2 O dynamics, this study provides a robust quantitative basis for improving predictive models and informing management strategies that align legume-based agriculture with both climate mitigation and food security objectives.