Composting efficency of indigenous and introduced earthworms

Abstract

Eight species of earthworm belonging to three families were identified from five different soil types of southern Kerala. The identified species were Megascolex cochinensis, M.konkanensis, M.trivandranus, M.trilobatus, Perionyx, sansibaricus, Pheretima heterochaeta (Megascolecidae), Pontoscolex corethrurus (Glossoscolecidae) and Drawida sp. (Moniligastridae). M.cochinenses and corethrurus were ubiquitous. P. sansibaricus was confined to forest soil and red soil. Forest soil with high water holding capacity, organic carbon content and acidic pH had the highest total count of worms and the highest species diversity. The exotic species Eudrilus eugeniae was more efficient for composting in terms of duration for composting and biomass production. However, the multiplication rate of the indigenous P. sansibaricus was more than that of E.eugeniae. In field conditions, when the same weight of worms was used, the time taken for composting was found equal for E. eugeniae and P. sansibaricus. However, the biomass recovery of earthworm was more in E. eugeniae. Both species performed well in the rainy season, compared to hot summer months. The breeding potential, time required for composting and decomposition rate were significantly superior from june to September. There was posititve correlation between juvenile count and rainfall and negative correlation with maximum temperature with respect to E.eugeniae. In P. sansibaricus adult and juvenile counts expressed positive correlation with rainfall and humidity and negative correlation with maximum temperature. Space was found to be a determining factor in the growth and multiplication earthworms. The cocoons of E.eugeniae required 29+ 1.10 days for hatching. The hatching rate was only 56.25 + 1.19 percent in laboratory condition. The mean number of juvenile hatched /cocoon was 2.88+0.35. The period required to attain reproductive stage was 43.38 + 0.56 days. Cocoons of P.. sansibaricus was elongate and slender. The time required for hatching of cocoon was 16+0.43 days. The hatching rate was 64.06+3.44 percent in laboratory conditions. The juveniles required 38.25 + 0.70 days to become adults. The number of cocoon laid / week was also significantly superior, as compared to E. eugeniae. Vermicompost along with full inorganic fertilizer increased the yield by 21.4 per cent and 19.0 percent in bittergourd and cowpea, respectively. In cowpea, application of vermicompost without inorganic fertilizer was equally effective as that of the recommended manorial schedule. There was significant yield increase when vermicompost was used as a potting mixture in bhindi. However, no significant difference in the biometric characters of plants was observed. Vermicompost along with full inorganic fertilizer increased the yield of bhindi by 15 percent. The effect of in situ vermiculture (250 worms of p. sansibaricus /plot) was on par with that of package of practices recommendations. Neemcake was found beneficial for supporting growth and multiplication of E.eugeniae. Neem cake recorded 102 percent increase in juvenile worm production. Neem leaves and thevetia leaves were equally effective. Mahua cake was not supportive for growth and multiplication. Neem cake was effective in supporting growth and multiplication of P.sansibaricus. Neem cake recorded 52 percent increase in juvenile worm production. Leaves of neem, clerodendron and glyricidia were equally effective in supporting juvenile worm production as that of the control. Calotropis leaves and mahua cake caused significant reduction in adult, juvenile and cocoon production. In a pot culture study, among the treatments, carbofuran, phorate and quinalphos, quinalphos(0.5 kg and 1.0kg ai/ha) was found the least toxic to earthworm and there was total survival after an interval of seven days. The treatments involving earthworms for composting evolved significantly higher Co2 during the period of composting, compared to the control treatment of banana: cowdung mixture without worms. The Co2 evolved by the treatments involving E.eugeniae and P.sansibaricus were on par. Maximum Co2 evolution was observed on the 21st day which was significantly superior to the Co2 evolution estimated at various other intervals. From the 21st day onwards a decline in the CO2 evolution was recorded. The treatment involving earthworms had a significantly higher bacterial, fungal and actinomycetes counts, as against the treatment without worms. The highest fungal count for E.eugeniae was found on the 28th day. Towards compost maturity the fungal counts were more or less steady; however, a slight increase in the count was observed on the 56th day. There was no definite trend with respect to actinomycetes count during the period of composting.