Abstract: Amendment application combined with vegetation restoration is an economical and effective approach to improve the hostile habitat conditions of bauxite residue sites. In this study, different compound amendments (e.g., wood vinegar, phosphogypsum, mushroom residue, sewage sludge, cow manure, and fish manure) and ryegrass (Lolium perenne) were used as experimental materials for phytoremediation of bauxite residue. A 90-day pot experiment was conducted to investigate the effects of amendment-plant combined remediation on the physicochemical property, enzyme activity, and microbial community structure of bauxite residue. The results showed that single application of wood vinegar and phosphogypsum could regulate the alkalinity of bauxite residue, with pH being decreased by 4.1% and 11.4%, respectively. However, lower nutrient availability hindered the stable growth of plants. The amendment-plant combined remediation decreased pH and exchangeable sodium percentage of bauxite residue from 9.8 to 7.6-7.8 and from 29.3% to 25.9%-28.2%, respectively. Additionally, the amendment-plant combined remediation significantly increased nutrient contents (available nitrogen, available phosphorus, total nitrogen, total phosphorus, and organic matter), enzyme activities (urease, catalase, alkaline phosphatase, and sucrase), and diversity and relative abundance of microbial communities in bauxite residue. The dominant bacterial phyla were Proteobacteria, Actinobacteriota, Bacteroidota, and Firmicutes, while the dominant fungal phylum was Ascomycota. Overall, the amendment-plant combined remediation significantly improved physicochemical property, enzyme activity, and microbial community structure of bauxite residue, which is of great significance in comprehensively indicating the soil formation processes of bauxite residue.

Key words: bauxite residue, compound amendment, vegetation restoration, physicochemical property, enzyme activity, microbial community