Quantifying microbial necromass contributions to soil carbon sequestration under diverse cropland management practices: A meta-analysis

Under the dual challenges of global climate change and agricultural sustainability, cropland soils, as critical carbon (C) sinks, have garnered significant attention regarding the stabilization mechanisms of their organic C pools. Existing studies indicate that the stable organic C pool in cropland soils primarily originates from the accumulation of microbial necromass, a process strongly influence by agricultural management practices. However, there remains a notable knowledge gap regarding how various management strategies influence microbially turnover and necromass formation mechanisms. This study integrates 1082 globally distributed paired experimental datasets to establish the quantitative framework linking microbial necromass dynamics with multi-scale management practices. The results showed that the greatest increase in microbial necromass C (MNC) content (42 %) was obtained when mineral and organic fertilizers were combined. Individually, the application of manure, straw, and green manure boosted MNC by 28 %, 9 %, and 31 %, respectively. Conservation tillage and crop rotation increased MNC by 20 % and 14 %, respectively. A pivotal advancement lies in elucidating the lagged formation of microbial necromass relative to living biomass turnover and demonstrating the superior coupling effects of integrated management strategies over singular practices. Interactions among climatic, soil physicochemical and microbial properties regulated the necromass formation pathways and organic C accumulation. Appropriate management strategies can boost C sequestration in cropland soils by facilitating microbial necromass accumulation, offering potential benefits at both regional and global scales.