Estimation of Soil Erodibility and Rainfall Erosivity for the Biemso Basin, Ghana

2012

English

In the agroecological zone of the Biemso basin in the Ashanti Region of Ghana, soil erodibility and rainfall erosivity patterns were estimated. The study aimed at investigating the temporal variability of rainfall erosivity using the Fournier Index Method and assessing the soil erodibility parameters of a Sawah site using the WEPP model. Four plots representing the major land uses in the area for maize, oil palm, natural vegetation and plantain cultivation were selected. Results showed that soil organic matter content ranged from 1.95 to 5.52%; sand ranged from 14.34 to 31.86 %; silt ranged from 31.63 to 68.77%; clay ranged from 16.04 to 20.08% and very fine sand from 3.38 to 8.84%. The derived interrill erodibility (Ki) values ranged from 44.26 to 51.70 kg s m-4 under all land uses considered at the study site and soils in the study area were moderately resistant to erosion by raindrops. The derived rill erodibility (Kr) values ranged from 0.005 to 0.012 s m-1 under all land uses considered at the study site. Rill erodibility values were higher at the foot slopes under all land uses except under Oil Palm land use. Rainfall values exceeded the 20-25 mm threshold value for erosive rains. Erosivity values determined for the study site revealed a moderate erosion risk in the major rainy season (April-July); low erosion risk in the minor rainy season (August-October ) and very low erosion risk in the dry season (November-March). It is recommended that soil and land management practices that would reduce water erosion during the major rainy season should be implemented such as bunding, mulching and contour farming.

Baffour, N. K.; Atakora, E. T.; Ofori, E.; Antwi, B. O.