Characterization and Evaluation of Inland Valley Watersheds for Sustainable Agricultural Production: Case Study of Semi-deciduous Forest Zone in the Ashanti Region of Ghana.

Abstract

As a part of efforts to effectively utilize inland valleys of Ghana for sustainable agricultural production while also protecting and conserving the environment, the bio-physical nature of a benchmark site in a semi-deciduous forest zone was characterized using the integrated transect method. Different valley types, first-, second-, and third-order inland valleys, were identified within the valley system. The main soil types identified were Ferric Lixisol, Ferric Luvisol and Haplic Gleysol in the upland, fringe and valley bottoms, respectively. The soil reactions for both the upland and lowland soils were slightly acid (pH 4.8-5.9) in the topsoil to strongly acid (pH 4.0-4.3) in the subsoils. Available P (Bray 1) was lower in the upland and lowland soils. Effective cation exchange capacity (ECEC) and levels of exchangeable Ca, Mg, and K were higher for the valley bottom soils than the upland soils. The total nitrogen levels of both upland and lowland soils, however, were higher in the topsoils but lower in the subsoils (0.84- 0.02%). Generally, the soil fertility status of the lowland soils was slightly higher than the fertility status in the uplands. The upland soils were well drained, while the valley bottom soils were poorly drained. The water table exhibited a cyclical movement of surfacing in the rainy season and going into a trough in the dry season. The valley bottoms are used mainly for cultivating rice in the wet season and vegetables in the dry season, while the uplands are used mainly for cereals, root and tubers, and plantation crops. The percentage of the land overall covered by primary and secondary forest was estimated to be less than 20%. The main identified constraints on the utilization of the inland valley watersheds are soil degradation in the uplands and water control and soil fertility maintenance in the valley bottoms.