Effects of vermicompost organic fertilizer on sulfamethoxazole removal performance and microbial community structure in farmland soil

【Objective】 This study aimed to investigate the effects of different vermicompost organic fertilizer doses on sulfamethoxazole degradation and the changes in microbial community structure in farmland soil， to screen the optimal dose of vermicompost organic fertilizer for the best degradation effect and types of degrading microorganisms， providing theoretical basis for optimizing the remediation effect of sulfamethoxazole-contaminated farmland soil. 【Method】 Different doses （1%， 2%， 3%， 4%） of vermicompost organic fertilizer were added to investigate the sulfamethoxazole removal efficiency， soil physicochemical properties， enzyme activities， and the changes in soil microorganisms during the remediation of farmland soil， and analyze the correlations between sulfamethoxazole residual concentration， environmental factors， and soil microorganisms. 【Result】 By increasing pH， organic matter content， and humus content， vermicompost organic fertilizer accelerated sulfamethoxazole degradation in farmland soil. Adding 2% vermicompost organic fertilizer yielded the best effect， as the sulfamethoxazole degradation rate reaching 82.8%. After the end of the culture period， the pH was 6.51， the organic matter content was 21.08 g/kg， and the humus content was 14.52 g/kg when adding 2% vermicompost organic fertilizer， showing increases of 7.43%， 3.84%， and 11.35% compared with the vermicompost-free treatment （CK） respectively. Meanwhile， vermicompost organic fertilizer enhanced the activities of peroxidase， urease， and dehydrogenase in soil， and promoted the increase in abundance of the potential sulfamethoxazole-degrading microorganisms， such as Nocardioidaceae， Methylobacteriaceae， Intrasporangiaceae， Xanthobacteraceae， Geobacteraceae， Micromonosporaceae， and Comamonadaceae. Correlation heatmap analysis indicated that Methylobacteriaceae， Nocardioidaceae， Intrasporangiaceae， Geobacteraceae， Nitrobacteraceae， Gemmatimonadaceae， pH， organic matter， humus， urease， catalase， and dehydrogenase were negatively correlated with sulfamethoxazole residual concentrations. 【Conclusion】 Applying vermicompost organic fertilizer to sulfamethoxazole-contaminated farmland soil can improve soil physicochemical properties （pH， organic matter， and humus） and soil enzyme activity to increase the relative abundance of sulfamethoxazole-degrading microorganisms， promoting the sulfamethoxazole removal in farmland soil， with adding 2% vermicompost organic fertilizer yielding the best effect.