Growth and elemental uptake of Rhodes grass (Chloris gayana) grown in a mine waste-contaminated soil amended with fly ash-enriched vermicompost

Vegetation cover in mine waste-affected soils is necessary to ensure sustainability of these fragile ecosystems. This study evaluated the potential of fly ash-enriched vermicompost (FV) to improve growth of Chloris gayana in a gold mine waste-affected soil. The treatments in the study were based on optimizing phosphorus supplied as vermicompost at 20 mg P and 40 mg P per kilogram soil which were compared to triple super phosphate (TSP) applied at 40 mg P/kg. The 40-mg P/kg FV treatment resulted in 38.4%, 164% and 182.5% significant increase in shoot height, shoot biomass and root biomass, respectively, relative to the control. The increased biomass was reflected in the plant tissue analysis where 40 mg P/kg FV had high P, Ca, Mg and K, though not significantly different to the 20-mg P/kg FV treatment. Amendment effect had no influence on plant tissue N, Pb, Cd and As. Chloris gayana uptake of Fe, Mn, Zn and Cr was significantly reduced with addition of the vermicompost, whereas Cu and B were significantly increased in the 40-mg P/kg FV treatment relative to the control though the increases did not exceed the critical concentration limits of these elements. Therefore, re-vegetation of mine waste-contaminated soils can be achieved with addition of FV at a rate of 40 mg P/kg FV. However, more studies may need to be done under field conditions to further evaluate the effectiveness of such vermicomposts in improving the re-vegetation capacity of mine waste-contaminated soils.