Tillage practices affect the synergetic relationship between soil organic carbon and crop yield under straw return

Straw returning is a pivotal strategy to enhance soil organic carbon (SOC) concentration and crop yield. However, the synergy between these two outcomes and its spatial variability under different tillage practices remain poorly quantified. Therefore, we conducted a meta-analysis using 1767 paired observations from 222 studies in China, including 726 SOC comparisons and 1041 yield comparisons, with 428 observations contributing to both analyses. Observations with complete baseline soil data were then combined with harmonized gridded spatial predictors to generate scenario-based adaptation maps. Our findings demonstrate that straw return significantly increased SOC concentration by 10.66% and crop yield by 7.96% compared to straw removal, with a significant positive correlation between the two responses. The strength of this synergy, however, was strongly modulated by crop type and tillage practice, and differed between topsoil and subsoil layers. Notably, subsoiling (SS) and no-till (NT) more frequently produced simultaneous benefits for both SOC and yield, whereas conventional tillage (CT) and rotary tillage (RT) showed greater variability. However, these estimates carry uncertainty due to uneven observational coverage for certain crops and the inherent limitations of grid-based environmental data. Our findings suggest that strategic combinations of straw return with appropriate tillage and crop selection can effectively reconcile SOC concentration with productivity goals. We conclude that region-specific adaptation is essential for sustainable agricultural management under straw return.