Effects of Tillage Practices on Soil Organo-Mineral Complexes and Organic Carbon Distribution Under Continuous Maize Cropping in the Black Soil Region of Northeast China

Organo-mineral complexes are intimately involved in protecting the stability of soil organic carbon (SOC), as they are influenced by environmental factors such as pH and redox conditions, as well as by the implementation of appropriate management practices. Nevertheless, the mechanism between environmental factors and the fractions of organo-mineral complexes, as well as their response to tillage practices, remain poorly understood. This study investigated the effects of rotary tillage (RT), plow tillage (PT), and no-tillage (NT) on organo-mineral complexes (water-dispersible G0 fraction, sodium-dispersible G1 fraction, grinding-dispersible G2 fraction) and their organic carbon (OC) in the black soil region of Northeast China in 2002 and 2022. Compared to 2002, the content of organo-mineral complexes and their OC in 2022 increased by 5.54% and 3.15%, respectively. Relative to PT, RT and NT increased the organo-mineral complex content by 0.39% and 8.40%, and increased the OC content by 9.41% and 20.56%, respectively. Between 2002 and 2022, tillage measures led to greater contributions of organo-mineral complexes to soil carbon sequestration. RT and PT primarily enhanced the contribution rate of the G0 fraction, whereas NT resulted in enhanced contribution rates for both the G0 and G1 fractions. This suggests NT is most conducive to transforming SOC into stable organo-mineral complexes. Redundancy and correlation analyses identified exchangeable Ca²⁺ in G1, pH, clay, TP, along with iron and aluminium oxides, as key environmental factors influencing the transformation pathways among the complexes fractions.