Effect of Agricultural Management on ¹⁴C-Erythromycin Transformation in Soil: Linking Antibiotic Fate with Microbial Community Dynamics

Erythromycin, a widely used macrolide antibiotic, frequently enters agricultural soils through organic amendments (e.g., manure, sludge) and wastewater irrigation. However, the influence of agricultural management practices on the fate of such antibiotics in soil is poorly understood. In this study, we employed 14C-erythromycin to explore its transformation and fate under different agricultural management practices, including chicken manure amendment, activated sludge amendment (surface or mixing applications), and flooding. Erythromycin was rapidly mineralized in the unamended soil (t1/2 = 7.5 days, 91.8% at 120 days). However, the addition of chicken manure or flooding significantly inhibited the mineralization (47.3 and 69.0% at 120 days, respectively), promoted bound residue formation, and extended its half-life to 23.7-36.8 days. In contrast, activated sludge amendment enhanced erythromycin transformation with mixing applications (t1/2 = 7.2 days), while the surface application had limited effect (t1/2 = 8.0 days). High-throughput sequencing analysis revealed that these practices significantly altered soil microbial communities, and in particular, fluctuations in the abundances of Proteobacteria, Firmicutes, and Actinobacteria may have influenced erythromycin transformation. These findings underscore the urgent need to understand the environmental fate and risks of antibiotics under different agricultural practices and identify management practices that can effectively reduce antibiotic persistence and protect environmental health.