Fertilization and aridity legacies determine microbial necromass persistence across cropland climates

Microbial necromass-mineral interactions are vital for soil organic carbon (C) persistence, but their response to climate and fertilization legacies in croplands remains unclear. Using six long-term field sites (27–38 years) across a pronounced aridity gradient, we show that stabilization of microbial necromass by short-range ordered (SRO) minerals dominates in humid zones (aridity index, AI < 1.3) but progressively decouples under aridity (AI > 1.3). This decoupling challenges mineral-associated C paradigms in drylands. While climate (AI) governed mineral weathering and SRO abundance, fertilization management can supersede aridity-driven constraints on necromass C accrual. Spatial mapping of 6,060 in situ μ-FTIR spectra revealed reduced organic C degradation in outer aggregate rims under aridity, aligning with diminished microbial processing and necromass-SRO decoupling. Our findings establish soil moisture as a critical regulator of fertilization-induced ecological memory in mineral-necromass interactions, urging climate-tailored practices to enhance soil C resilience in water-limited ecosystems under global aridification.