Abstract:

Optimized management of legume green manure and nitrogen (N) fertilizer can enhance soil biological health and support sustainable crop production, yet how their interaction reshapes soil microbial communities and network complexity remains unclear. We hypothesized that 30% N reduction combined with mixed legume green manure improves soil quality and wheat yield by enhancing nutrient, enzyme activity, and microbial network complexity. To test this, a split-plot field experiment was conducted with two N rates (225 kg N ha~1, N2; and 158 kg N ha 1, a 30% reduction, N1) and two green manure systems (common vetch monoculture, CV; common vetch x hairy vetch, CV x HV). Our findings revealed that compared with N2CV, the N1CV x HV increased topsoil organic carbon, total nitrogen, available nitrogen, and urease activity. Higher urease activity indicates enhanced N mineralization potential, while the enrichment of key bacterial phyla (e.g., Proteobacteria and Myxococcota) directly participates in nitrogen transformation and indirectly enhances nitrogen availability through microbial lysis, supporting greater organic matter decomposition and nitrogen turnover capacity. N1CV x HV enriched nitrogen metabolism pathway, potentially linking network complexity to enhanced N transformation. These complementary microbial shifts and higher network complexity might jointly enhance soil nitrogen supply and wheat yield, resulting in significantly higher SOI and grain yield under NICV x HV than N2CV. We conclude that 30% N reduction with mixed legume green manure increases wheat yield by enhancing soil nutrients and bacterial network complexity. This study provides mechanistic insights into how integrated nutrient management builds healthier, more productive soils for sustainable intensification of cereal systems.