Characteristics and Classification of the Soils of Gonde Micro-Catchment, Arsi Highlands, Ethiopia

Abstract

Samples were collected from genetic horizons of representative soil profiles to study the morphological and physicochemical characteristics and to classify the soils of Gonde micro-catchment in Arsi highlands (Ethiopia) located at 70° 32’ 24” to 70° 34’ 28” N and 39° 13’ 15” to 39° 19’ 02” E. The study identified Humic Eutric Nitisols, Humic Epidystric Nitisols, Humic Orthidystric Nitisols, Humic Umbrisols and Grumic Mesotrophic Vertisols. Vertisols were found on flat slopes with imperfect drainage. Nitisols occupied the rolling and undulating slopes marked with reddish, very deep and well-drained soils. Umbrisols were distributed on the summit and shoulder positions of the landscape. Variability in soil characteristics largely depended on drainage, topography and land use patterns. Uncultivated Humic Umbrisols showed darker colour, soft consistence and lower bulk density values, whereas cultivated Nitisols had high bulk density values and reddish brown colours. The texture of surface horizons ranged from loam in Umbrisols to clay loam in Vertisols and Nitisols. Organic carbon was highest in Vertisols (6.35%) and ranged from 2.76–4.35% in Nitisols. Total nitrogen varied from 0.24–0.69% for the surface horizons. The highest cec (49 Cmolc (+) / kg of soil) was recorded in A horizon of Umbrisols and the lowest (21 Cmolc (+) / kg of soil) in Humic-Epidystric Nitisols. The exchangeable K was in high range, while available P was low to medium ranging from 1.18–8.04 mg/kg for surface horizons. All studied soils were acidic (pH 5.1–5.6). In general, soils had low base saturation suggesting that the soils of the study area were more constrained by low fertility condition than physical properties alone.