Abstract

The environmental interactions between plastics and pesticides in agricultural soils remain poorly understood. This 120-day microcosm study evaluated the individual and combined effects of polyethylene (PE), polybutylene adipate terephthalate (PBAT), and glyphosate on alkaline soil. Results revealed a short-term, microbially mediated synergistic degradation between plastics (especially PBAT) and glyphosate, achieving degradation rates of 17.6–28.5% for plastics and 77.2–94.7% for glyphosate. This process was driven by a reconfigured microbial network, characterized by enhanced community complexity, enrichment of dual-function taxa ( Sphingomonas (genus), Pseudomonadota (phylum)), and formation of functional complementary co-enriched Bradyrhizobium (genus) and putative degrader taxa. However, this pollutant-driven microbial specialization triggered a significant ecological trade-off, that accelerated co-degradation was accompanied by a 4.9–11.7% decrease in soil organic matter (OM) and a 25.1–28.6% increase in total nitrogen (TN) accumulation. Co-contamination also increased soil electrical conductivity (EC) by 15.2–17.9% and significantly activated key enzymes including lipase. Further network analysis and KEGG-based functional prediction showed stronger potential microbial associations under co-contamination. These changes may help explain the enhanced degradation of glyphosate and plastic films. However, co-contamination was also accompanied by altered predicted C/N/P cycling potential, soil nutrient imbalance, and increased predicted greenhouse-gas-related functional potential. Partial least squares structural equation modeling (PLS-SEM) analysis revealed that divergent relationships between glyphosate degradation rates and microbial activity under co-contamination with different types of plastics. This work provides a critical theoretical foundation for assessing the combined ecological risks of plastic films and pesticides and for guiding sustainable agri