Effects of Municipal Sludge Application on Composition and Microbial Communities of Mine Waste Rock Soil
The rapid population growth and accelerating urban development have made the comprehensive utilization of municipal sludge (MS) an urgent challenge. MS contains substantial organic matter and essential nutrients for crop growth, making it a promising soil amendment for the ecological restoration of mine waste rock. However, research evaluating the impact of MS application on soil health and ecological safety from a soil microbiology perspective remains understudied. Therefore, this study investigated the effects of MS and composted municipal sludge (CMS) on the ecological restoration of mine waste rock soil through pot experiments. High-throughput sequencing technology was employed to analyze changes in soil microbial community structure and diversity. Finally, network analysis and correlation heatmaps were utilized to elucidate the microbial driving mechanisms. The results indicated that after MS and CMS application, organic matter content increased from 20.38 g/kg (Level 3) to 38.52 g/kg (Level 2). The levels of available nitrogen, phosphorus, and potassium rose from Level 4, 6, 2, to Level 1, 4, 1, respectively. Fresh weight, aboveground height, root length, and stem diameter of ryegrass all increased significantly. Venn diagram and heatmap analyses indicated that lower application rates (<1.5 kg/m²) enhanced microbial community richness and diversity. This study confirms municipal sludge as an effective amendment for mine waste rock soil. It is recommended to limit application rates below 1.5 kg/m² in practical mine ecological restoration projects, with particular attention to long-term dynamics of heavy metals and salinity to ensure safe and sustainable land reuse.