Soil pH amelioration fosters persistent carbon sinks through mineral stabilization and aggregate protection

The stability of soil organic carbon (SOC) is fundamental for the integrity of agricultural carbon credits but remains challenging to verify and predict. A persistent methodological challenge lies in isolating the specific effect of soil pH amelioration from confounding factors like organic matter inputs. Here, by applying bivariate linear mixed-effects modelling to a global synthesis of 180 field trials, we quantitatively disentangled the effects of pH amelioration on SOC components across a stability continuum from bulk soils to aggregate fractions. pH amelioration enhances bulk SOC stocks by 18 – 20%, with mineral-associated organic carbon and microbial necromass carbon significantly increasing by 11 – 15% and 12 – 19%, respectively. Simultaneously, pH amelioration restructures soil architecture toward enhanced aggregate stability, preferentially enriching carbon within microaggregates (up 44% in alkaline soils). Structural equation modelling confirms that this process is hierarchically driven by pH-induced shifts in microbial biomass and aggregate stability. Our findings suggest that pH amelioration is a fundamental process engineering persistent carbon sinks by directing carbon flow into mineral-stabilized and physically protected pools. This work repositions precision pH management as an essential ecological engineering strategy, and provides a mechanistic foundation for transitioning carbon credit protocols from stock-based accounting to stability-centric verification.