Mining wastes are of environmental concern due to the potential threat to the surrounding environment and public health. Revegetation of mining waste is required to achieve long term stabilization and simultaneously improve ecosystem services and rural economies. In this study, mining waste was collected from a lead mine tailings pond and a pot experiment was conducted to investigate the potential of mycorrhiza and other amendments to assist plant growth on lead mining waste and their influence on soil microbial activity. In addition to control (unamended tailings) treatment and arbuscular mycorrhiza fungi (AMF) treatment, the mine tailings were also amended with two levels of biosolids (BS) (equivalent to 25 and 40 dry tone/acre) alone or in combination with other amendments such as AMF, biochar (BC), and humic substances (HS) to grow willows, poplars, and miscanthus. Each treatment and plant species was replicated 6 times. After approximately 6 month growth period, the plants were harvested and the aboveground biomass was determined. Plant roots were then collected for biomass determination along with sampling of fresh fine root tips for AMF colonization estimation. Bulk and rhizosphere soil samples were collected for dehydrogenase activity (DHA) testing to measure microbial enzymatic activities, which are considered good indicators of changes in soil quality.
Results/Conclusions
The control treatment resulted in very low biomass production and severe nutrient deficiency symptoms for all three plant species. Adding AMF alone did not significantly enhance plant growth for any of the three species. However, BS application resulted in a highly significant increase in biomass compared to control treatment for the three species. Combination of BS+AMF further increased biomass production for all three plant species. The most significant influence of BS+AMF treatment was determined with miscanthus species resulting in (>50 fold) increase in dry biomass compared to control treatment. Combination of BS+HS further increased willows biomass (>22 fold) compared to control. AMF colonization was observed on all three plant species with high infection rates in all treatments except the control. BS+BC treatment had a high AMF infection rate even though this treatment did not receive AMF inoculum. Adding only AMF did not significantly improve soil DHA compared to the control which had very low DHA measurement for the three plant species. Soil DHA increased significantly in the rest of the treatments. A negative correlation between AMF root colonization rate and soil DHA was found indicating that AMF competing with soil microbes.