Rice Cultivation Duration Drives Soil Organic Carbon Stabilization in Saline–Alkaline Paddy Soils via Mineral-Associated Organic Carbon Accumulation and Biological Pathways

Abstract

Simple Summary Soil salinization severely reduces agricultural productivity and soil carbon sequestration potential. Based on a 12-year rice cultivation chronosequence in saline–alkaline paddy soils of western Jilin, China, we examined soil organic carbon stabilization dynamics and underlying mechanisms. Continuous rice cropping markedly alleviated saline–alkali stress, decreasing topsoil EC by 70.11% and increasing soil organic carbon (SOC) by 63.09%. SOC was progressively converted to stable pools, with topsoil mineral-associated organic carbon (MAOC) increasing by 147.12%. This shift was driven by improved soil physicochemical conditions and enzyme-mediated microbial processes, which facilitated the formation of mineral-protected, aromatic-stabilized organic carbon. Our results confirm that rice cultivation serves as an effective practice to restore degraded saline–alkaline soils and enhance stable soil carbon sinks.