Effect of Earthworm Activity on Soil Properties in Different Land Use Systems in Abakaliki.

A study was carried to determine the effect of earthworm activity on soil properties in four different land use systems comprising , alley cropping system, forest, fallow and continuous cropping lands in Abakaliki, Ebonyi State, Nigeria. Earthworm casts and their dry weights were highest in the forest than in any of the other land use systems. Casting activity changed the soil particle size distribution towards a higher silt content than in the non-ingested soils in the forest soils. The soil bulk density was lowest in the forest soil (1.18 g M-3) and 1.04 g M-3 in the casts from the forest soils relative to the non-ingested soil in 2007 and 2008 respectively. Total porosity, water-stable aggregates and soil moisture content were highest in the earthworm casts than in the non-ingested soils. Water- stable aggregates were linked to the organic matter content. In 2008, the casts from the forest with the highest organic matter had 23% increase in water-stable aggregate over the levels in the non-ingested soils. Infiltration processes were highest in those land use systems with higher number of earthworm casts. Organic matter increased in the casts with time in the forest, fallow, and alley cropping system but decreased in the continuous cropping. Soil pH in the casts of the alley cropping system remained moderately acid in 2007 and 2008 (pH 5.7 and 5.8) but in the casts of the forest and the continuous cropping it remained very strongly acid and extremely acid respectively. Available P was in the order of alley cropping > fallow > forest > continuous cropping soils. In all, soil nutrients content were highest in those land use systems with the greatest number of earthworm casts.