Effects of Municipal Sludge Application on Composition and Microbial Communities of Mine Waste Rock Soil

• • MS and CMS application increased soil organic matter from 20.38 g/kg (Level 3) to 38.52 g/kg (Level 2), a 89% relative increase, directly improving soil fertility for vegetation establishment in mine waste rock. • • Available nitrogen, phosphorus, and potassium levels improved from Level 4, 6, and 2 to Level 1, 4, and 1 respectively, indicating a significant nutrient boost that supports plant growth and reduces the need for synthetic fertilizers. • • Ryegrass growth metrics (fresh weight, aboveground height, root length, and stem diameter) increased significantly, demonstrating the agronomic efficacy of MS and CMS as soil amendments. • • Microbial community richness and diversity were enhanced only at application rates below 1.5 kg/m²; higher rates suppressed microbial diversity, highlighting a critical threshold for safe application.