Assessment of the Role of Four Species of Earthworm in the Bioremediation of Allelopathic Weeds Salvinia and Ipomoea

Abstract

The study explored for generating vermicompost from Salvinia, Four species of earthworm (E.andrei, P.sansibaricus, L.rubillus and D. Willis) were explored for the direct vermicomposting of ipomoea. The succulent parts of the weed were utilized in high-rate vermireactors without any pre-composting, manure supplementation, or any other form of pre-treatment. All vermireactors were operated uninterruptedly for 160 days. In the first series of experiments vermicomposting of ipomoea was studied with adult earthworms which had been born in cow-dung fed cultures and had grown to adulthood in them. The second series utilized earthworms born and raised in ipomoea-fed cultures. Their next generation was then used for the third series of experiments. These studies enabled us to see whether the second and the third generations display increasing adaptation to the ipomoea feed. The studies revealed that, For each of the four species of earthworms studies by us, successive generations can be raised with ipomoea as the sole feed. secondly, The individuals of all the four species when grown on ipomoea as the sole feed were as healthy and reproductive as the ones grown on animal manure were. Third successive generations got increasingly acclimatized to ipomoea and displayed increasing efficiency in vermicomposting ipomoea. Forth the reproductive ability of all the four species in ipomoea-fed reactors increased as they produced their second and the third generation in it. A comparison between the results of the experiments on vermicomposting of Salvinia with the findings on ipomoea revealed an interesting trend. Even as the quantities of the two weeds converted to vermicompost per unit time by each adult earthworm of a given species were quite similar, the extent of reproduction achieved in ipomoea by all the four species was much lesser than that which was achieved in ipomoea. It indicated that either the adaption to ipomoea vis a vis reproduction is slow and may take several generations to peak, or that some chemicals in ipomoea suppress earthworm fecundity.