Residual polyethylene film loading alters soil quality and maize productivity, with distinct bacterial communities in...

Residual polyethylene (PE) film can alter soil resources and crop production, but its effects across loading levels and at the soil-film interface remain poorly resolved. In a maize field experiment established in 2011 in northwestern China, we assessed soil properties, bacterial communities, nitrogen cycling indicators, and crop performance across five PE loadings (0-600 kg ha^-1). Soil firmly adhering to residual film was pooled across the four film treatments to characterize plastisphere soil. Soil quality and maize performance responded nonmonotonically to loading. Grain yield was 20% higher at 150 kg ha^-1 and 22% lower at 600 kg ha^-1 than in the control. At the highest loading, lower nutrient levels and root biomass coincided with greater soil water content after harvest and lower bacterial network connectivity. Pooled plastisphere communities showed greater diversity and contrasting assembly patterns. Their higher connectivity did not consistently correspond to greater simulated robustness. Plastisphere soil had higher nitrification potential than bulk soil, despite lower summed nitrification gene abundance than at 300 and 450 kg ha^-1. Structural equation modeling linked yield positively to total nitrogen and available phosphorus. These findings identify loading and microbial differentiation at soil-film interfaces as complementary dimensions of residual-film impacts.