Soil resource filtering links microbial functional strategies to maize productivity under long-term tillage and residue management

Long-term tillage and residue management alter soil resource environments, but how these contrasting resource contexts relate to microbial functional configurations and crop productivity remains unclear. We evaluated an eight-year field experiment in a maize Mollisol agroecosystem in Northeast China, comparing conventional ridging with residue removal and stubble cleaning, wide–narrow row management with high-stubble retention and reduced tillage, no-tillage with high-stubble and root retention, and moldboard plowing with root-stubble incorporation after aboveground residue removal. Soil physicochemical properties, shotgun metagenomes, and maize yield were integrated to quantify two axes of metagenomic functional potential: carbon processing (R/L), expressed as selected oxidative/aromatic C-processing functions relative to polysaccharide-hydrolysis functions, and phosphorus cycling (O/I), expressed as selected phosphatase-related functions relative to intracellular P-turnover functions. Long-term management differentiated bacterial community composition and Kyoto Encyclopedia of Genes and Genomes (KEGG) Orthology (KO) functional profiles, with soil organic matter and available phosphorus representing major soil resource gradients. Available phosphorus was negatively associated with both strategy indices, whereas O/I increased with soil organic matter, indicating asymmetric alignment between resource status and C- and P-related functional allocation. Wide–narrow row management and no-tillage maintained relatively high maize yields but differed in dominant functional configurations: the former aligned with lower R/L under higher available phosphorus, whereas the latter aligned with higher O/I under higher soil organic matter. Exploratory path-model synthesis further suggested that maize yield was more closely associated with these functional configurations than with microbial biomass carbon. These results indicate that long-term tillage and residue management can create distinct soil resource contexts under which alternative microbial configurations align with maize productivity.