Earthworm Cast Biomass Under Three Managed Ecosystems: Implication for Soil Fertility

Abstract

The study was conducted to determine earthworm cast biomass under three managed ecosystems, Gmelina, Cashew and Banana plantations at Federal University of Agriculture, Abeokuta and its impact on the soil physicochemical parameters. Seven, five and four plots of 3 m² each were sampled in Gmelina, Cashew and Banana plantations respectively. Each plot was laid out in form of a grid and seven quadrats of 44 cm x 44 cm each were sampled in each plot. On-field Cast weights were determined to the nearest gram using a top loading mechanical balance and the cast biomass was calculated from these. The nutrient and mineral properties of both earthworm casts and parent soils were determined using standard methods of AOAC. The % OC (4.61), %OM (7.96), sulphate (38.37), pH (7.78), total nitrogen (0.27), Mn (0.47) and Fe (7.23) were significantly higher (p<0.05) in the earthworm casts under Gmelina plantation compared with the cashew and banana plantations. Cu and Fe concentrations in the parent soil under Gmelina plantation were significantly higher (p<0.05) than under cashew and banana plantations while Mg and Mn concentrations showed no significant difference. Compared with the parent soil, %OC, %OM, Mn and Fe obtained from earthworm casts were significantly higher (p<0.05) under all three plantations. Earthworm cast biomass under the Gmelina plantation (15483.63g/m²) was significantly (p<0.05) higher than that obtained under the cashew (13270.83g/m²) and banana (8828.13) plantations. The present results showed that earthworm activity is better supported under Gmelina than cashew and banana plantations In addition, the higher cast biomass and nutrient level in the parent soil under Gmelina plantation signifies a significantly higher nutrient level which, expectedly means that the Gmelina plantation soil will be more fertile than the soil in cashew and banana plantations.

Key Words: Earthworm cast, Gmelina, Cashew, Banana, physicochemical