Affects of adding coal gangue and coal slurry on the fertility of sandy soil and alfalfa yield

The large-scale discharge and accumulation of coal gangue and coal slurry not only occupy land, but also cause resource waste, and there is an urgent need for large-scale ecological utilization. The proportion of clay minerals and quartz in coal gangue and coal slurry from different production areas varies, and due to significant differences in composition, their comprehensive utilization pathways are also different. In this study, coal gangue and coal slurry rich in clay minerals are used as ecological restoration mineral materials, and different proportions of coal gangue and coal slurry are added to sandy soil in Horqin Sandy Land. Medicago sativa L. is used as the test plant to conduct pot experiments to explore the effects of coal gangue and coal slurry on the soil fertility, bioavailable phosphorus（BBP） components and alfalfa yield of the aeolian sandy soil in Horqin Sandy Land, providing a reference for the resource utilization of coal gangue and coal slurry and the restoration of sandy land. The results show that compared with the blank control（CK） without adding coal gangue and coal slurry, the addition of coal gangue and coal slurry improves soil physicochemical properties and increases soil bioavailable phosphorus content and alfalfa yield. Compared with the treatment of coal gangue or coal slurry alone, the improvement effect of the combination of the two is better. Under the condition of adding 10% coal gangue and 15% coal slurry, the soil comprehensive fertility index（IFI） and alfalfa yield is the highest, with an increase of 169.93% in IFI value and 76.38% in alfalfa yield. The content of four bioactive phosphorus（BBP） components, hydrochloric acid extracted phosphorus（HCl-P）, citric acid extracted phosphorus（Citrate-P）, enzyme extracted phosphorus（Enzyme-P）, and calcium chloride extracted phosphorus（CaCl₂-P）, is significantly increased by 36.23%, 26.30%, 246.07%, and 210.28%, respectively. Correlation analysis show that there is a good positive correlation between IFI value and alfalfa yield. Redundancy analysis show that Enzyme-P is a key factor in evaluating this improvement method, with a contribution rate of up to 87.0% to alfalfa yield and soil organic matter content. The mixed addition of coal gangue and coal slurry rich in clay minerals can significantly improve soil fertility and plant yield in sandy areas, and Enzyme-P content is the most critical factor affecting alfalfa biomass accumulation. This study provides a scientific basis for the resource utilization of coal gangue and coal slurry, as well as the improvement of sandy soil.