Abstract

In the sub-humid tropical Africa, the pressure of diminishing land resources resulting from the rapidly increasing population has made the traditional fallow systems used for the replenishing soil fertility impossible. Alley cropping has been suggested as an alternative to bush fallowing. This study evaluated the effects of 20 years of different species of hedgerow crops on the physical and chemical properties of soil. Soil physical and chemical properties were studied underPterocarpus santalinoides, Gliricidia sepium, Enterolobium cyclocarpum andLeucaena and leucocephala intercropped with maize (Zea mays L.) at a 20 years old Leventis Foundation Farm, at Ilesa in the south western part of Nigeria. Soil bulk density was significantly reduced under the hedgerow species from a maximum of 1.52 g cm^-3 under control to 1.33 g cm^-3 under Pterocarpus andEnterolobium hedgerows. While the soil cone penetrometer resistance index followed a similar trend, the soil field capacity was lowest under Pterocarpus and highest under Leucaena hedgerows. Soil porosity increased significantly (p < 0.05) from 0.38 under control to a maximum of 0.47 under Pterocarpus, while the hydraulic conductivity at a suction of -0.5 cm was significantly highest Gliricidiahedgerow. Soil pH and other chemical properties were consistently highest underLeucaena and consistently Gliricidia hedgerow. Overall among the screened hedgerow species, G. sepium showed the best promise in terms of improvement in both soil physical and chemical properties.

Key words: Hedgerow, alley cropping, hydraulic conductivity, Pterocarpus, Gliricidia, Leucaena, Enterolobium, cone penetrometer resistance, field capacity.