AM fungal and rhizobacteria jointly enhance vegetable waste decomposition in soils and harvest environmental and agronomic benefits in dryland

Returning tail vegetable residues to soil plays a critical role in water and nutrient recycling in drylands, yet it remains unclear whether an effective biological strategy can accelerate their decomposition. Here, we show that co-inoculation with arbuscular mycorrhizal fungi (AMF; Rhizophagus irregularis strain GSICC 63801) and plant growth-promoting rhizobacteria (PGPR; Bacillus amyloliquefaciens strain GSICC 32826) significantly enhanced tail vegetable residue degradation and carbon stabilization in a dryland wheat field across two growing seasons. Co-inoculation increased the degradation rate of vegetable waste by 20.6–38.4% relative to non-inoculated controls (CK) and sole inoculation. Co-inoculation produced greater upregulation of β-glucosidase (14–21.1%) and cellobiohydrolase (8.2–11.2%) compared to sole inoculation alone. Despite increasing soil respiration by 22.5–42.9%, co-inoculation improved photosynthetic rate by 35.5–42.6%, root biomass by 25.2–26%, and wheat grain yield by 43.4–50.6%. Relative to CK and sole inoculation, co-inoculation elevated root colonization by 84–94.6% and glomalin content by 18.3–18.6%. Microbial biomass carbon and nitrogen contents also increased by 21.7–24.2% and 31.5–37.9%, respectively. Conversion of labile to stable carbon pools was evidenced by increases in bacterial and fungal microbial residues (25–36.7%) and mineral-associated organic carbon (4.7%), indicating improved transformation of fresh organic inputs into persistent soil carbon fractions. Machine learning and structural equation modeling validated that AMF-PGPR co-inoculation enhanced stable carbon formation via microbial-mediated pathways. AMF-PGPR co-inoculation increased soil organic carbon and total nitrogen content. Thus, AMF-PGPR co-inoculation accelerates vegetable waste decomposition, delivering combined environmental and agronomic benefits for dryland agriculture.