Abstract

Soil microbial communities are essential for ecosystem functioning, yet their responses to combined abiotic stressors remain unclear, as most studies focus on single-stressor effects. In this work, the combined effects of different drought levels and co-contamination with copper nanoparticles and the fungicide carbendazim on microbial community structure and function in an agricultural soil over 120 days were evaluated. Enzymatic activities, potential nitrification rate, and functional gene abundances (16S and amoB) were measured. Moreover, 16S rRNA metabarcoding was applied to explore microbial diversity and community dynamics comprehensively. Pesticide dissipation kinetics were also assessed. General metabolic and nutrient-cycling enzymes were susceptible to combined stress under SD and ED. Although alpha and beta diversity showed limited differences at the end of the experiment, co-occurrence networks revealed progressive increases in microbial connectivity and negative correlations, indicating structural reorganization. Functional predictions highlighted a shift from nitrogen and phosphorus cycling toward carbon-degradation pathways, suggesting stress-induced trade-offs. Significantly, pesticide dissipation was markedly reduced under SD, with prolonged half-lives and higher residues, reflecting impaired microbial degradation capacity. Collectively, our results demonstrate that drought is the dominant driver of microbial reorganization, amplifying the effects of emerging contaminants on microbial interactions, functional potential, and pollutant fate. © 2025 Elsevier B.V.