Insights of the co-existing fertilizers enhance metolachlor persistence in soil: perspectives from mobility, metabolism, and microbiome

Co-existence of fertilizers in farmland might change the biodegradation of pesticides. The effects of nitrogen (N), phosphorus (P), potassium (K), compound fertilizers (NPK), chicken manure (CM), plant ash (PA) on the environmental behaviors of metolachlor (MET) were investigated. The sorption of MET was reduced by N and NPK at 1 mg/g, but enhanced by CM and PA at 10 mg/g in soil, while the vertical migration was inhibited by the four fertilizers. The fertilizers inhibited biodegradation and prolonged the half-life of MET above 3 times. To explore the microbial mechanism, correlation analysis revealed that 9 potential MET-degrading genera were reduced by fertilizers, thus inhibiting the metabolic pathways [MET oxanilic acid (MOA) and ethane sulfonic acid (ESA)] and prolonging the persistence of MET. In summary, nitrogen fertilizers may increase the soil residual of MET, whereas CM and PA reduce the risk by immobilization and inhibiting metabolic transformation.