Comprehensive chemical leaching, phytoremediation, organic amendment and nitrification inhibitor enhancing tailing soil remediation and ecosystem multifunctionality

Unreasonable mining and excavation of rare earth caused considerable threats to agricultural production and local ecology. This study explored the optimized combination of chemical leaching, phytoremediation, organic amendment and nitrification inhibitors to decline lead (Pb) contents in mining-affected soils but to enhance soil ecosystem multifunctionality. In comparison to control (CK) in the citric acid-leaching group, soil available Pb contents were significantly decreased by 15.7%, 17.5% and 18.4% in the ryegrass + camellia shell (RS), ryegrass + camellia shell + nitrification inhibitor dicyandiamide (RSDC) and ryegrass + camellia shell + nitrification inhibitor 3, 4-dimethylpyrazole phosphate (RSDM) treatments, respectively. Meanwhile, soil Firmicute ratios of the RS, RSDC and RSDM treatments were higher than those in the CK treatments, indicating that an increase in soil Firmicute ratio could improve soil health. Co-presences of shell and nitrification inhibitor significantly increased the height and weight of ryegrass in the double-distilled water and citric acid-leaching groups, and they also promoted soil ecosystem multifunctionality notably. Although the ryegrass did not survive in the citric acid and EDTA-2Na + citric acid-leaching groups, the shell amendment and nitrification inhibitor additions notably improved soil Shannon diversity indices and biotic community network stabilities. Soil pH, β-glucosidase, urease, microbial community diversity, Firmicute and Actinobacteriota ratios were negatively related to soil available Pb contents. Our study indicated that the combination of citric acid-leaching + ryegrass + organic shell + DCD was an optimal strategy for decreasing heavy metal risks and enhancing soil ecosystem health in abandoned mining areas. • Optimizing combinations reduced Pb content but enhanced ecosystem multifunctionality. • Leaching agent citric acid was selected based on trade-off of plant growth and Pb removal. • Organic amendment and nitrification inhibitors notably increased soil multifunctionalities. • Shell and nitrification inhibitor additions promoted biotic community network stability. • Soil pH and Firmicute were significantly negatively relate to available Pb content.