Legume Rotations and Conservation Tillage in Synergy: Yield Gains, Carbon Sequestration, and Climate Resilience.

Leguminous crop rotation (LC) and conservation tillage (CT) are nature-based solutions to mitigate climate change. Previous studies have shown significant variations in crop productivity and soil organic carbon (SOC) under LC and CT, largely influenced by site-specific conditions. However, the mechanisms driving the interactions between LC and CT to enhance compatibility across diverse environmental conditions remain unclear. This study conducted a meta-analysis combined with machine learning, using a high-resolution global database of 271 site experiments to evaluate the impact of LC, CT, and their interaction on crop yield and SOC, clarify the underlying mechanisms, and assess their global potential. Results indicated synergistic effects of LC and CT led to additional increases of up to 13.4% in yield and 8.6% in SOC. These benefits were more pronounced in warm-humid regions, with low initial soil fertility, fine soil texture, and low nitrogen (N) input. Among key factors influencing these interactive effects, N input and the initial soil carbon to nitrogen (C/N) ratio emerged as the top two determinants for crop yield and SOC changes. Globally, integrating LC and CT in farmlands could potentially increase crop production and SOC stock by 16.9% and 7.6%, respectively. Looking ahead, these practices could enhance crop production by up to 400 Tg (24.6%) and SOC stock by 8.4 Pg (10.0%), helping to address climate change under various future scenarios. These results highlight that optimising N input and the initial soil C/N ratio through LC-CT integration achieves a win-win scenario of increased crop yield and enhanced SOC sequestration, with significant potential under future climate conditions. This study provides a scientific basis for developing targeted farmland management strategies tailored to diverse environmental conditions worldwide.