Soil restoration in rare earth tailings: Synergistic effects of coal gangue-based silicon fertilizers

The growing demand for rare earth elements has intensified environmental concerns in mining areas, particularly with respect to soil contamination by heavy metals and nutrient imbalances. This study investigated the potential of coal gangue-based silicon fertilizers (CG-SF) for the remediation of ion-type rare earth tailings soil (RETS). CG-SF was applied at various concentrations in controlled pot experiments, with ryegrass cultivation used as a bioindicator of soil health. The results demonstrated that CG-SF significantly improved the soil physicochemical properties, increased pH, CEC, and OM content, while enhancing water retention and nutrient availability. Additionally, CG-SF reduced the bioavailability of heavy metals by promoting their immobilization in stable soil fractions. Soil enzyme activities, particularly dehydrogenase, were stimulated, indicating enhanced microbial activity and nutrient cycling. The results of PiecewiseSEM suggested that silicon fertilizer primarily facilitated the ecological restoration of ion-type rare earth mining areas by enhancing the growth of ryegrass and improving soil chemical properties. This study highlights the dual benefits of CG-SF in recycling industrial waste and providing a sustainable, cost-effective solution for soil remediation in mining areas. The findings underscore its potential for large-scale application in ecological restoration and sustainable land management.