Changes in microbial properties after manure, lime, and bentonite application to a heavy metal-contaminated mine waste

Organic materials improve soil properties conducive to plant growth and may be necessary to stabilize lead (Pb) and zinc (Zn) mine wastes. Composted beef manure was applied to mine wastes at two sites at 45 and 269 Mg ha(-1) with and without lime and bentonite. Switchgrass (Panicum virgatum) was established as a vegetative cover. Compost significantly increased waste nutrient content, pH, and available water, and decreased heavy metal availability. The largest total phospholipid fatty acid (PLFA) increase was in the high compost treatment, with values of 80.3 and 30.2 (site A) and 84.9 and 23.1 (site B) mu mol kg(-1) soil for treated and control, respectively. However, high rates of compost (269 Mg ha(-1)) were generally required to increase bacterial and fungal communities beyond the control. The high compost-treated waste exhibited increased arylsulfatase, phosphatase, and beta-glucosidase enzyme activities. Observed increases in pH may have resulted in lowered enzyme activity in the low compost treatment. Results suggest that an organic matter addition above 45 and up to 269 Mg ha may be needed to support and sustain microbial activity and biomass in mine waste materials, at least over the two year period evaluated. Published by Elsevier B.V..