Agricultural wastes improve soil quality and enhance the phytoremediation efficiency of economic crops for heavy metal-contaminated soils in mining areas

In recent years, global attention has increasingly focused on soil heavy metal (HM) contamination. However, there remains a paucity of studies examining the interaction effects of agricultural wastes as amendments in HMs contaminated soil, particularly concerning the utilization of economic crops for soil remediation. This study investigates the impacts of various agricultural wastes (soybean meal, peanut bran, oak leaves, and coffee grounds) on soil properties, plant growth, and HMs accumulation in economic crops (sugarcane and cassava) through pot experiments. The application of these amendments resulted in significant increases in soil pH, soil organic matter (SOM), and cation exchange capacity (CEC) content. Moreover, catalase and urease activities in sugarcane planting soil were enhanced by 2.73-32.53% and 84.07-132.74%, respectively, with differing effects observed in cassava planting soil. Applications of oak leaves and coffee grounds inhibited soil invertase activity (by 28.78-61.95%), whereas soybean meal and peanut bran stimulated invertase activity (by 28.18-122.05%). Overall, these amendments reduced the bioavailability of HMs in the soil, with soybean meal demonstrating the most significant reduction in the effective state HMs content in sugarcane planting soil. The pot experiment results demonstrated that soybean meal and peanut bran, as soil amendments, improved soil quality, and promoted the growth of sugarcane and cassava. Additionally, they also increased the accumulation amount of Cd, Pb, and Zn in the plants, thereby enhancing the effectiveness of phytoremediation in HM-contaminated soils. Consequently, this study provides practical insights for soil safety and cleaner production in HMs contaminated karst farmland.