Nutrient availability of earthworm casts collected from under selected woody agroforestry species

Abstract

Pot experiments were carried out to assess the nutrient availability of earthworm casts (wormcasts) of Hyperiodrilus africanus that were collected from plots of Dactyladenia barteri, Leucaena leucocephala and Treculia africana grown on an Alfisol (Oxic paleustalf) as affected by drying and grinding, different periods of pre-incubation of ground wormcasts, and fertilizer application. Experiments were carried out using a double pot technique and rice (Oryza sativa) was used as test crop. Wormcasts had a higher nutrient status than corresponding surface soils. Rice grown on wormcasts produced higher shoot dry weight and showed higher nutrient uptake, lower fertilizer response than rice grown on surface soils. Poor rice growth and nutrient uptake when grown on unground wormcasts are attributed to high bulk density of the wormcasts. Preincubation of the wormcasts did not benefit the crop. Drying and grinding and fumigation of wet wormcasts improved rice plant growth and nutrient uptake.