Microbial Community Structure and Metabolic Pathways Influence the Enrichment of Stable Dissolved Organic Matter Under Long‐Term Conservation Tillage Practices in Sloping Farmlands

ABSTRACT

Long‐term conservation tillage (CT) practices profoundly influence soil carbon sequestration, yet their molecular‐level effects on dissolved organic matter (DOM) stability and associated microbial mechanisms in erosion‐prone slopes are poorly characterized. Here, we integrated ultrahigh‐resolution mass spectrometry and amplicon sequencing in a typical global erosion zone (red‐soil hills, southern China) after 20‐year CT practices. Results showed CT practices significantly elevated soil organic matter and transformed DOM composition toward lipid‐, protein‐ and lignin‐like compounds. Microbial diversity substantially increased, with bacterial and fungal genera rising by 23.4%–35.9% and 46.2%–124.4%, respectively. DOM molecular profiles correlated strongly with microbial community structure and metabolic pathways, particularly aromatic degradation, carbohydrate metabolism and pentose phosphate pathway. These findings indicated that long‐term CT practices, especially contour tillage combined with straw mulching, enhanced DOM stability and soil carbon sequestration through microbial regulation. This provides a science‐based and transferable strategy for combating land degradation and supporting climate adaptation in vulnerable landscapes worldwide.