Associations between soil microbiomes and carbon stabilization under long-term no-till farming systems in the Argentine Pampas

Soil microbial communities play a key role in carbon (C) cycling in agroecosystems; however, their long-term responses to contrasting management practices remain poorly understood in agricultural soils. In this study, we evaluated the effects of more than 20 years of no-till farming (NTF) and conventional tillage (CT) on soil physicochemical properties, bacterial and fungal community composition, and inferred functions related to C and nutrient cycling in the Argentine Pampas. We show that NTF increased total organic carbon (TOC) stocks in surface soils and promoted edaphic conditions associated with C stabilization, including higher cation exchange capacity and structural stability. Bacterial communities exhibited high functional redundancy and were primarily structured along sodium-related parameters, whereas fungal communities were more sensitive to management, with NTF favoring ligninolytic and symbiotic fungi that contribute to necromass formation and long-term carbon stabilization. In contrast, CT enriched opportunistic fungal guilds associated with disturbance and short-term nutrient turnover. Phylogenetic analyses revealed community assembly dominated by environmental filtering in both microbial domains. Overall, these results highlight the central role of fungi as mediators of soil C stabilization and suggest that conservation practices such as NTF enhance microbiome contributions to ecosystem services and climate change mitigation in intensively managed agroecosystems.