Impact of Type and Rate of Application of Biochar on Earth Worm (Eisenia felida) and Some Chemical Properties of a Savannah Haplic Acrisol in Ghana

Abstract

The use of biochar as soil amendment to improve the fertility and productivity of soil and to sequester C is attaining interest in Ghana. However, little is known about possible adverse impacts on soil biota in the Tropics. Two sequential incubation mesocosm experiments respectively were used to determine the toxicity of biochar prepared from corn cob (CCB) and poultry manure (PMB) on Eisenia fetida earthworms and also the interactive effect of biochar and earthworm on earthworm casting activity and selected soil properties.

After 42 days of incubation, significant (p < 0.05) and inverse relationship was found between biochar application rates and earthworm survival which negatively correlated in the range of (r = – 0.90 to – 0.95, p < 0.01) and (r = – 0.88 to – 0.94, p < 0.01) for CCB and PMB respectively. Fifty percent survival of earthworm was observed at respective biochar application rates below 78 t ha^-1 for CCB and that of PMB was 52 t ha^-1.  After 56 days of incubation, casting activity correlated negatively with increasing biochar concentrations (r = -0.66, p < 0.01) with casting activity reducing by 68.4 % to 77.9 % in CCB amended soils and 79.6 - 81.3 % in PMB amended soils. It was also demonstrated that biochar and earthworm synergistically increased pH, mineral nitrogen, available phosphorus, total organic carbon, cation exchange capacity and microbial biomass carbon significantly in the mesocosm.