Integrating legumes into cropping systems enhances soil carbon and nitrogen content while reduces the soil carbon-to-nitrogen ratio: A global meta-analysis

The source data of "Integrating legumes into cropping systems enhances soil carbon and nitrogen content while reduces the soil carbon-to-nitrogen ratio: A global meta-analysis ". Legume integrated into cropping systems (LIS) offer a promising strategy to mitigate the decline in soil fertility caused by continuous agricultural intensification. Assessing the effects of LIS on soil carbon and nitrogen dynamics, as well as the influence of site-specific factors globally, is crucial for developing regionally tailored cropping system strategies. Therefore, we conducted a global meta-analysis of 1199 observations from 173 field experiments to evaluate LIS impacts on soil carbon and nitrogen under diverse management practices and environmental conditions. Our results showed that LIS significantly increased the soil organic carbon (SOC) and soil total nitrogen (STN) content by 4.60% and 7.90%, respectively, while reducing the soil carbon-to-nitrogen ratio (SCN) by 2.37%. Changes in SOC and STN due to legume integration were positively correlated with mean annual precipitation (MAP) and mean annual temperature (MAT), but negatively correlated with initial SOC (SOCi) and initial C:N ratio (CNi). Integrating legumes as cover crops led to greater increases in SOC and STN, whereas the reduction in SCN was more pronounced when legumes were used as main crops. Moreover, SOC and STN increased when legumes replaced fallow or gramineous soil, whereas SCN significantly decreased only when legumes replaced gramineous systems. Furthermore, the benefits of LIS on SOC and SCN were amplified by greater crop diversity. Overall, these findings provide a comprehensive understanding of how legume integration improves soil nutrient status and supports the development of more sustainable agricultural practices.