Conservation Tillage Increases Carbon Storage by Regulating Mineral‐Mediated Aggregate Stability and Carbon Chemistry

ABSTRACT Widespread adoption of conservation practices is increasingly encouraged to improve soil organic carbon (SOC) storage and mitigate climate change. However, soil texture and mineralogy cause variable SOC responses under conservation tillage. The role of minerals and organic carbon composition in soil aggregation and SOC stabilization remains insufficiently understood. This study evaluated the long‐term effects of conservation tillage (no‐tillage with straw return, NTS) versus conventional tillage (plough tillage with straw removal, CT) on carbon storage across Phaeozems, Calcaric Cambisols, and Calcic Luvisols. Compared to CT, NTS increased the annual average C sequestration rate by 15.3%–76.7% and SOC storage by 10.2%–28.4% in different soil types. NTS also increased macroaggregate percentage and mean weight diameter (MWD), resulting in 17.8%–28.3% larger macroaggregate‐associated SOC and total nitrogen (TN) contents. Notably, the aromatic‐C/aliphatic‐C ratio under NTS increased in bulk soil and macroaggregates, which were positively correlated with larger amorphous iron (Feo) content, Ca 2+ concentration, and specific surface area in different treatments. Phaeozems exhibit the largest SOC storage, along with larger Feo and Ca 2+ contents and aromatic‐C/aliphatic‐C ratio. However, NTS led to the greatest increases in MWD and SOC storage in Calcaric Cambisols, and the greatest enhancement of microbial biomass carbon in Calcic Luvisols. PLS‐PM analysis indicated that although the aromatic‐C/aliphatic ratio directly enhances aggregated stability, Feo and Ca 2+ promoted MWD indirectly by facilitating greater aromatic‐C and polysaccharide‐C. Overall, conservation tillage promoted selective binding of Feo and Ca 2+ to SOC functional groups, thus enhancing soil aggregation and SOC physico‐chemical protection, with calcareous soils showing a stronger response.