Characterization and Classification of Soils of Selected Areas in Southern Ethiopia

Abstract

Characterization and classification of soils previously conducted in southern Ethiopia were not detail and could not give adequate information for further researches. Hence, this study was conducted in Taba, Huletegna Choroko, Tenkaka Umbulo, Kontela, Alage and Jole Andegna, southern Ethiopia, to make detail assessment of morphological and physicochemical properties and investigate the types of soils of the areas for research purpose. Two representative pits of 2 x 2 x 2 m were excavated at each location and the profiles were described in situ. Soil samples were collected from each identified horizon and analyzed for macro- and micro-nutrients status, organic carbon, pH, CaCO₃ and soil texture. The soils in all locations are very deep (>150cm), have well-developed structure and Bt subsurface (argic) horizons (except Alage and Kontela soils) indicating the occurrence of clay translocation within the profiles. Calcium carbonate accumulations were found in Kontela, Alage and Tenkaka Umbulo soils that resulted in occurrence of calcic subsurface horizons. The soils of the study areas have different textural classes varying from sand to clay. The soils in all locations had pH>7.4 and high base saturation (>60%). Generally, the soils contained medium organic carbon (1.5-2.5%) and medium to high total nitrogen (0.2-0.5%) at the surface and low at the subsurface horizons. The cation exchange capacity ranged from medium to very high (5-25 to >40 cmol (+)/kg soil), the medium range being dominant. Iron (Fe), zinc (Zn) and copper (Cu) were low in Tenkaka Umbulo and Huletegna Choroko soils, whereas manganese (Mn) was high at the surface and low in subsurface horizons. In Taba soils, Cu was deficient throughout the profiles, whereas Fe, Zn and Mn were high in the surface and low in subsurface horizons. Soils of Jole Andegna contained low Fe, and high Cu and Mn, whereas Zn content was high in the surface but low in the subsurface horizons. The soils were classified according to the World Reference Base for soil resources as Haplic Calcisols (Humic) in Tenkaka Umbulo, Haplic Lixisols (Siltic) and  Haplic Lixisols (Humic) in Taba, Andic Lixisols (Humic) and  Andic Cambisols (Humic) in Huletegna Choroko, Luvic Calcisols (Siltic) in Kontela, Haplic Calcisols (Chromic) in Alage and Haplic Luvisols (Humic) in Jole Andegna. The varying properties, fertility status and types of soils identified in the study areas provide adequate information to design soil management options and further researches on the soils of each site. Therefore, application of site specific soil fertility management practices and conducting researches, which can improve soil micronutrient status and nutritional quality of crops are essential.

Key words: soil properties, soils horizons, soil profiles, micronutrients, soil types