Effects of different amendments on the quality of coal gangue artificial soil.

The crushing of coal gangue with amendments enables its transformation into usable artificial soil for solid waste recycling. However, current research on the selection, proportioning, and corresponding improvement effects of amendments remains insufficient. In this study, we comprehensively evaluated the improvement effects of different ratios of three amendments (biochar, super absorbent polymer, cow manure) through complete combination testing and principal component analysis combined with a minimum dataset. The results showed that: 1) Among the amendments tested, cow manure exhibited the most significant improving effect on coal gangue. Compared to coal gangue, cow manure application alone or in combination with other amendments notably increased soil indices (total nitrogen, available nitrogen, total phosphorus, available phosphorus, available potassium, phosphatase, catalase, protease, amylase). Available phosphorus increased by 19.7%-290.4%, available potassium increased by 311.1%-744.4%, phosphatase showed increases of 70.2%-320.8%. The application of biochar and super absorbent polymer could also promote the increase of indicators such as total phosphorus, available potassium, catalase, dehydrogenase, and protease, but the enhancement magnitude was lower than that of the cow manure treatment group; 2) The five indicators sorted by weight in the minimum dataset were available potassium, total phosphorus, total nitrogen, protease and dehydrogenase; 3) The combination of super absorbent polymers and cow manure achieved the highest soil quality index. An optimal scheme incorporating 6% biochar, 0.7% super absorbent polymers, and 10% cow manure was identified for effective improvement. These findings provide a theoretical basis and practical guidance for optimizing coal gangue reuse and promoting ecological restoration in mining areas.