Effects of Amendments on Soil Microbial Diversity, Enzyme Activity and Nutrient Accumulation after Assisted Phytostabilization of an Extremely Acidic Metalliferous Mine Soil

Current criteria for successful phytostabilization of metalliferous mine wastelands have paid much attention to soil physico-chemical properties and vegetation characteristics. However, it remains poorly understood as to how the soil microbial community responds to phytostabilization practices. To explore the effects of amendments on the microbial community after assisted phytostabilization of an extremely acidic metalliferous mine soil (pH < 3), a pot experiment was performed in which different amendments and/or combinations including lime, nitrogen-phosphorus-potassium (NPK) compound fertilizer, phosphate fertilizer and river sediment were applied. Our results showed the following: (1) The amendments significantly increased soil microbial activity and biomass C, being 2.6–4.9 and 1.9–4.1 times higher than those in the controls, respectively. (2) The activities of dehydrogenase, cellulase and urease increased by 0.9–7.5, 2.2–6.8 and 6.7–17.9 times while acid phosphatase activity decreased by 58.6%–75.1% after the application of the amendments by comparison with the controls. (3) All the amendments enhanced the nutrient status of the mine soil, with organic matter, total nitrogen and total phosphorus increased by 5.7–7.8, 3.1–6.8 and 1.1–1.9 times, relative to the mine soil. In addition, there were strong positive correlations between soil microbial community parameters and nutrient factors, suggesting that they were likely to be synergistic. From an economic view, the combination of lime (25 t ha−1) and sediment from the Pearl River (30%) was optimal for functional rehabilitation of the microbial community in the extremely acidic metalliferous mine soil studied.