Characterization of Soils along a Toposequence in Gununo Area, southern Ethiopia

Abstract

Six soil profiles of different landscapes, representing convex crest, top-slope, mid-slope and depression, were studied along a toposequence, to assess the influence of topography and management practice on soil characteristics in the Gununo area of S. Ethiopia. The soil profiles on the convex crest, at the low side of the terrace on mid-slope and depression had deep, dark surface layers as compared to the others, and the continuous deposition of soil material on the depression had led to lithological discontinuity. Clay migration and coatings were observed in the subsurface layers of the pedons, except in the pedon in the depression. Generally, the soil structure was angular to sub-angular blocky with varying grades. The dry consistency of the soils in the surface layers was by and large slightly hard, whereas the moist consistency was invariably friable. The wet consistency indicated various degrees of stickiness and plasticity. The soils were slightly to moderately acidic (pH <6.4), with CEC ranging from 21.3 to 44 cmolc kg-1 and high in exchangeable Mg on the surface layers. The organic C and total N were low to medium, although the C:N ratio was almost optimal. The available P of the surface layers was low to very low (2.2–4.6 mg kg-1), except for the soils of the pedon on the convex crest, which had 7.8 mg P kg-1, whereas exchangeable K contents were below the critical limit in some of the pedons. The results revealed that slope and management practices influenced soil properties, suggesting the need for development and/or adoption of appropriate management options for varying slope gradients.