Characterization and classification of soils of upper Hoha sub-watershed in Assosa District, Western Ethiopia

Abstract

Characterization and classification of soils is a major tool for understanding the nature and status of soils. The objective of the study was to characterize, classify and map the soils of Upper Hoha sub-watershed according to the World Reference Base for Soil Resources [1]. Seven representative pedons were opened in Upper Hoha sub-watershed at different landscape positions. Accordingly, the surface soils of Pedon 2, 3, and 7 consisted of Mollic horizons; whereas Pedon 1, 4, 5 and 6 had Umbric horizons. The subsurface diagnostic horizons identified for the opened pedons were Nitic, Cambic, Ferralic, Plinthic and Pisoplinthic horizons. Pedon 1, 2, 4, 5 and 7 contained a Nitic horizon; whereas, Pedon 3 and 6 had Cambic horizons. Also Pedon 3, 4 and 6 had Plinthic, Ferralic and Pisoplinthic subsurface horizons respectively. The surface soils of Pedon 1, 2 and 4 showed anthric properties which is affected by long-term plowing; and Pedon 2, 5 and 6 showed sideralic properties in the subsurface soils which had lower CEC <24 cmolc kg−1 clay. Pedon-3 and 7 showed abrupt textural difference in clay content between surface and subsurface horizons; in particular, Pedon-7 had colluvic materials deposition. As a result, soils of Upper Hoha sub-watershed were classified in reference soil groups of Nitisols, Cambisols and Plinthosols with their corresponding qualifiers.