Growth, reproduction, and life cycle of Eudrilus eugeniae in cocoa and cashew residues

Cocoa and cashew residues are lignocellulosic fibrous materials produced in huge quantities, in West Africa, posing disposal problems thus threatening environmental health. Decomposition of these residues in the field is slow due to their complex chemical composition. Vermicomposting is an eco-friendly technology that converts organic biomass into nutrient-rich organic fertilizers. The growth, reproduction, and life-cycle of Eudrilus eugeniae, in cocoa and cashew residues, were evaluated under laboratory conditions to assess the viability of recycling these residues via vermicomposting. Two hatchlings were introduced into 100 g of cocoa, cashew, and a mixture of both residues after two weeks of traditional pre-composting. Earthworms' weight gain, mortality, sexual maturity, and cocoons production were monitored periodically for 21 weeks. No mortality was observed in any of the residues. The maximum weight gain and the highest growth rate were observed in cashew residues. Net biomass gain per worm was 1.04 +/- 0.29 g in cocoa residues, 1.71 +/- 0.22 g in cashew residues, and 1.19 +/- 0.30 g in the mixture of both residues. The number of cocoons produced per worm per day in cashew residues (0.28 +/- 0.03) was significantly higher than those observed in cocoa residues (0.17 +/- 0.02) and in the mixture of the two residues (0.21 +/- 0.01). Statistically, number of cocoons produced per worm per day in cocoa residues was significantly lower than that obtained in the mixture of the two residues. The results suggested that both cashew and cocoa residues or their 1:1 mixture are viable growth and reproduction media for E. eugeniae, and hence both are potential substrates for vermicomposting with E. eugeniae.