Integrated organic-inorganic fertilization enhances soil microbial diversity and mitigates the yield-quality trade-off in pakchoi (Brassica chinensis L.)

The sustainability of agricultural production systems is increasingly constrained by the trade-off between yield and quality, largely driven by declines in soil microbial diversity under conventional intensive management characterized by excessive synthetic fertilizer inputs. This study elucidates the synergistic mechanisms through which integrated low-rate inorganic-organic fertilization (IO1) alleviates this trade-off in pakchoi ( Brassica chinensis L .) by regulating rhizosphere microbial communities. A hierarchical pathway model was developed to quantify the linkages among soil microbial diversity, crop growth dynamics, yield formation, and quality attributes. Compared with inorganic-only fertilization (I1), the IO1 treatment significantly enhanced bacterial Shannon diversity and Chao1 richness, which accelerated the average growth rates of plant height (0.736 cm/d) and leaf area index (0.121 cm 2 /(cm 2 ·d)). As a result, pakchoi yield increased to 5.58 kg/m 2 , representing a 24.77 % improvement over I1. At the mechanistic level, improved microbial functional balance optimized nitrogen metabolic pathways, leading to substantial increases in soluble sugars (64.37 %), soluble proteins (39.21 %), and vitamin C content (82.04 %), while simultaneously reducing nitrate accumulation by 14.78 %. Mantel test results further revealed that bacterial communities primarily governed biomass accumulation through fresh weight dynamics (4.239 g/(plant·d)), whereas fungal communities played a key role in regulating photosynthate redistribution via organic matter catabolism, thereby establishing a "growth prioritization-quality compensation" dynamic equilibrium. Model predictions indicated that each unit increase in bacterial Shannon diversity corresponded to a 0.534 kg/m 2 increase in yield, while each unit rise in the Pielou evenness index resulted in a 2.218 mg/g reduction in nitrate content. Overall, these findings provide a robust theoretical basis for microbial driven precision fertilization strategies aimed at enhancing yield, quality, and sustainability in vegetable production systems.