Influence of carbon-based organic fertilizer on soil microorganisms and vegetable growth in Sb-As co-contaminated soil: a synergistic mechanism of promotion and detoxification.

BACKGROUND

Antimony (Sb) and arsenic (As) co-contamination threatens crop production and food safety. Carbon-based organic fertilizers may simultaneously improve soil fertility, regulate microbial communities, and reduce metal(loid) mobility, but their performance in Sb-As co-contaminated vegetable systems remains unclear.

METHODS

A pot experiment with pak choi was conducted to compare different carbon-based amendments, including magnesium sulfate-loaded biochar-based organic fertilizer (CBOF-M). Soil chemistry, pore-water elements, enzyme activities, rhizosphere microbial communities, plant growth, and elemental accumulation were evaluated.

RESULTS

Carbonaceous amendments reduced Sb mobility but increased As solubility. CBOF-M increased soil carbon, produced the highest plant biomass, reduced Sb translocation to edible tissues, and enriched Bacteroidota and Gemmatimonadota. Structural equation modeling identified an indirect microbiome-mediated pathway and a direct enzyme-mediated nutrient-cycling pathway.

CONCLUSION

Magnesium sulfate-loaded biochar-based organic fertilizer produced a promotion-detoxification synergy, although As mobilization remains a key constraint requiring formulation-specific control.