Effect of tillage and woody hedgerows in alley cropping on the productivity of an Alfisol

Multipurpose woody species can play an important role in the improvement and maintenance of soil productivity in traditional and planted fallow systems. This study examined the longterm effects of woody species grown in hedgerows in alley cropping and of soil tillage, on soil properties, runoff and erosion, and crop performance. Observations conducted from 1988 to 1993 on a trial established in 1982 on a sloping land is reported in this paper. Six land use systems were compared: Leucaena leucocephala and Gliricidia sepium hedgerows planted at 2 and 4 m interhedgerow spacings and tilled, and no-till and tilled controls without hedgerows.The presence of hedgerows and no-till treatments maintained higher soil organic carbon (Org. C) and exchangeable cations contents. Highest Org. C and exchangeable cations were observed in plots with 4 m Leucaena hedgerows. Treatments with hedgerows also showed lower soil bulk density than the controls. The no-till treatment showed the highest soil bulk density. No relationships were observed between soil bulk density, aggregate stability and infiltration rate. Mean maize yields for the five years showed the following order: 4 m Leucaena > 4 m Gliricidia > 2 m Leucaena > 2 m Gliricidia > no-till > control tilled control plots. Intercropped cassava root yields showed the highest stability in the three cropping seasons in the tilled control and Gliricidia alley cropped plots. Lower cassava root yields were attributed to soil compaction in no-till treatment and to shading with 2 m Leucaena alley cropping