Effects of Soil Modification Materials on the Quality of Sandy Soil in Mine Dumps

Large-scale coal mine dumps are formed during the mining process of coal resources. These coal mine dumps comprise impoverished soil, posing significant challenges for vegetation restoration. To address this problem, soil microbial (EM) agents and fly ash have effectively improved soil quality. However, the effects of different application ratios on the quality of sandy soil in coal mine dumps are still unclear. This study aims to explore the applicable ratio for sandy soil in coal mine dumps. This study employed a field-based potted experiment design. A two-factor complete factorial experimental setup was utilized, with four levels of EM microbial agent to sandy soil weight ratio (0 g/kg, 0.1 g/kg, 0.2 g/kg, and 0.3 g/kg) and four levels of fly ash to sandy soil weight ratio (0 g/kg, 25 g/kg, 50 g/kg, and 75 g/kg), and the mixing of EM microbial agents and fly ash with the sandy soil was carried out at different ratios. Subsequently, the study examined the impacts of various dosages on the physicochemical properties of soil within the mine spoil heap, and a soil quality index was derived to quantify these effects. The application of EM microbial and fly ash resulted in significant improvements in the physicochemical properties of the soil compared to the control group. Notably, the combined application of EM microbial agent and fly ash exhibited superior effects on soil physicochemical properties compared to the individual applications of EM microbial agent or fly ash. Specifically, when the EM microbial agent concentration was 0.2 g/kg and the fly ash content was 75 g/kg, the enhancement in soil quality was most pronounced, with a soil quality index of 0.78. Mantel analysis revealed that the growth index and photosynthetic index of Corethrodendron fruticosum were primarily driven by soil total nitrogen and organic carbon. The research results can provide guidance and technical support for soil improvement in mining areas.