Reduction of bioavailability of heavy metals during vermicomposting of phumdi biomass of Loktak Lake (India) using Eisenia fetida

Abstract

Vermicomposting of phumdi biomass is a good alternative for protecting Loktak Lake and is advantageous for agriculture purposes. Research was carried out on bioavailability and leachability of nutrients (Na, K, Ca and Mg) and heavy metals (Zn, Cu, Mn, Fe, Ni, Pb, Cd and Cr) during vermicomposting of phumdi biomass for 45 days using Eisenia fetida earthworm. The bioavailability of heavy metals was determined in the form of water soluble and diethylene triamine penta-acetic acid (DTPA) extractable. The toxicity characteristic leaching procedure test was performed to determine the leachable heavy metals during the vermicomposting process. The concentration of nutrients increased during the process; whereas the concentration of water soluble, DTPA extractable and leachable heavy metals decreased significantly in all the trials. The vermicomposting of phumdi biomass by Eisenia fetida was very effective for the reduction of bioavailability and leachability of selected heavy metals. The leachability test confirmed that prepared vermicompost is not hazardous for soil, plants and human health. The possibility of using earthworms to mitigate the metal toxicity and to enhance the nutrient profile in phumdi biomass vermicompost, is advantageous in sustainable land renovation practices on a low-input basis.