Abstract

In the agroecological zone of the Biemso watershed area in the Ashanti region of Ghana, an estimination of soil erodibility and rainfall erosivity patterns was conducted. The study investigated the temporal variability of rainfall erosivity using the Fournier Index Method and assessed the soil erodibility parameters of sawah site using WEPP technology. Results obtained from the study showed that soil organic matter content ranged from 1.95 to 5.52%. The derived interrill erodibility (K_i) values ranged from 44.26 × 10⁵ to 51.70 × 10⁵ kg s m^-4 under all land uses considered in the study site and that soils in the study area were moderately resistant to erosion by raindrops. The derived rill erodibility (K_r) values ranged from 0.005 to 0.012 s m^-1 under all land uses considered in the study site. Rill erodibility values were higher at the foot slopes under all land uses except under Oil Palm land use. Rainfall values exceed the 20 to 25 mm threshold value for erosive rains. Erosivity values determined for the study site revealed a moderate erosion risk in major rainy season (April to July); low erosion risk in minor rainy season (August to October) and very low erosion risk in dry season (November to March).

Key words: Soil erodibility, rainfall erosivity, agroecological zones.