Composting–vermicomposting of leaf litter ensuing from the trees of mango (Mangifera indica)

Litter of the mango (Mangifera indica) tree leaves was composted and then converted into vermicast by the action of the earthworm Eudrilus eugeniae Kinberg. After over nine months of continuous operation the vermireactors with 62.5 animals l−1 generated 13.6 g vermicast per litre of reactor volume (l) per day (d) whereas the reactors with 75 animals l−1 produced 14.9 g vermicast l−1 d−1. This difference in performance of the reactors operating in duplicate at the two different earthworm densities was statistically significant ( 90% confidence level) for most of the nine-month span. The animals grew well in all reactors, increasing their zoomass by 103% and producing 157 offspring. Not a single of the 1100 animals died during the first four months. In the subsequent five months a total of 122 worms died, representing a loss of 2% per month. We attribute this to the normal process of ageing. The ability of the earthworms to survive, grow and breed in the vermireactors fed with composted mango tree leaves, and a rising trend in vermicast output inspite of the death of a few worms after four months of reactor operation, indicate the sustainability of this type of vermireactors. The studies also indicate that even better vermireactor efficiency may be possible by modifying the reactor geometry. Studies on changes in C:N ratio during composting and vermicomposting revealed that whereas composting helped in lowering the ratio due to loss of carbon in bacterial metabolism, vermicomposting had no such effect on the ratio.