Conservation Tillage-Mediated Rhizosphere Microbial Community Remodeling Drives Soil Organic Carbon Accumulation and Nitrogen and Phosphorus Transformation in Farmland

Conservation tillage has an influence on the cultivation and sustainable utilization of farmland. However, the microbial mechanism driving soil nutrient cycling in conservation tillage and its regulation pathway remain unclear. Based on a positioning experiment in black soil areas, this study systematically compared the effects of no-tillage (NT) and moldboard tillage (MT) combined with different straw returning amounts (straw non-returning, NS; straw half-returning, HS; straw full-returning, TS) on the composition of soil carbon (C), nitrogen (N) and phosphorus (P) and focused on the role of microbial community structure succession and functional changes in soil nutrient cycling. Microbial community remodeling driven by tillage measures was mainly regulated by C and N components. Bacterial modules 2 and 4 and fungal modules 1 and 2 were key for regulating the C, N and P cycle, of which 87 bacteria and 45 fungi taxa represented the core driving microorganisms. The total amount of no-tillage straw return reduced the formation and accumulation of labile organic carbon fractions by enriching yeast-like fungi and inhibiting the expression of complex organic matter decomposition genes. Tillage mainly promoted the accumulation of labile organic carbon fractions and nutrient release by regulating the bacterial community, while no-tillage straw returning promoted the accumulation of total organic carbon and organic nitrogen fixation by promoting the fungal community. This study revealed the biological pathway of conservation tillage that drives soil nutrient cycling by regulating key microbial communities. It also provides a microbiological basis for sustainable soil management in black soil areas.