Comparison of erodibility of some hararghe soils using rainfall simulation

Abstract

This paper reports an investigation on the comparative erodibility of three soil types occurring in the Hararghe Highlands, Eastern Ethiopia. Rainfall simulation at an intensity of 75 mm h− 1 was used to investigate runoff generation and sediment yield characteristics of the three soil types. Results were compared with soil erodibility calculated from measured soil characteristics such as silt content, organic matter content, bulk density, pH (H2O) and air-dry aggregates (0.6–0.2 mm). Aggregate stability index and shear strength measurements were used as surrogates for estimating erodibility. The three soil were not significantly different in their sediment yield and runoff generation characteristics. However, sediment yield was highest for the Fluvisol both under dry and wet soil conditions which is in agreement with its lowest shear strength. The high rock-fragment (stone content) of the Regosol had a confounding influence on the actual erodibility of the Regosol, while the relatively low air-dry aggregate (0.6–0.2 mm) content and high very fine sand and silt content of the Fluvisol rendered it to high sediment yield. Aggregate stability index was more in agreement with predicted erodibility than shear strength while shear strength was better related to sediment loss.