By Mba, Caroline C.
The peels of bitter cassava (Manihot utilissima) root, a major source of food carbohydrate
in the tropics, though rich in nutrients, form toxic wastes lethal to soil invertebrates and can
inhibit root growth. Recent investigations highlighted the ability of the earthworm, Eudrilus
eugeniue (Eug) to partially detoxify the toxic wastes, and transform the cassava peels into
valuable vennicompost. Vermicomposting and field investigations set up to assess the impact
of three agricultural wastes: poultry dropping (Capo), cowdung (Caco), and guava (Psidium
guajava) leaves (Cag) on Eug's ability to vermicompost cassava peel (Cas) and the biofertilizer
value of the vermicomposts produced, highlighted the beneficial effects of the waste
treatments and the efficacy of the biofertilizers in field plots cropped with cowpea. Cag and
Caco induced 55% and 64% greater Eug fecundity than Cas alone while (Capo) induced a 23%
reduction, Caco also induced 39% greater Eug biomass in compost cages. In the cowpea field
all vermicomposts treatments similarly enhanced earthworm surface cast production, but differed
in their effects on the diversity of the earthworm species: Capo and Cag induced 2120%
and 390% greater Irridodrillus spp. (earthworm) cast production. while Cas depressed
Irridodrillus surface activity. Capo induced 34% reduction on Aggrotoreutus nyongii (earthworm
spp.) activity relative to Cas, though the vermicomposts enhanced this earthworm
activity relative to the control. Cowpea aerial biomass increased significantly fivefold,
twofold, and 1.6-fold with Capo, Cas and Cag, over the untreated field plots. Soil CEC was enhanced with Cag, and available phosphorous increased twofold with Capo.