LAND USE TYPE AND LANDSCAPE POSITION EFFECTS ON SELECTED SOIL PHYSICO-CHEMICAL PROPERTIES:THE CASE OF OMANCHO WATER SHADE GURAGHE ZONE SOUTHERN ETHIOPIA

Abstract

Understanding the effects of landscape positions and land use type on soil properties is crucial for improving the soil productivity and to ensure the environmental sustainability. The objective of this study was to assess land use type and landscape position effects on selected soilphysico-chemical properties at Omancho watershed in Guraghe Zone of Southern Ethiopia. Accordingly, thirty six soil samples were collected from lower, middle and upper landscape positions and four land use types ( woodland, grazing land, conserved and non-conserved land) at the depth of 0-15 cm in three replications. Data on selected soil physico- chemical properties were collected and statistically analysed.The result showed that most of measured soil properties were significantly (p<0.05%)influenced by the interaction effects of topographic positions and land use types.The highest values of sand (46.67%) was recorded on non-conserved land of middle position, silt (33.67%) from grazing land at upper position and clay (57%) at lower position of grazing lands. The textural class in the study site was clay. The maximum (1.23gcm-3) and minimum (0.94gcm- 3) soil bulk density (BD) values were recorded under upper position of non-conserved and lower position of conserved land respectively. The total porosity varied from 54 to 64.5 % which was recorded from the upper position of grazing land and the lower position of woodland respectively. The result showed that soil BD and sand fraction decreased from upper to lower position. In contrast, total soil porosity, clay and silt were increased from upper to lower position. Compared to conserved/woodlands, the non-conserved lands revealed the hightest BD and sand fraction. Soil pH was varied between 5.9 and 7.4% from the upper position of non-conserved land and lower position of conserved lands, respectively. The highest base saturation (73.13%) was recorded from the lower position on woodland uses, whereas the least value (46.4%) was recorded from the lower position of non-conserved land. The higher Av.P (1.04mg/kg soil) was recorded from the lower position of conserved land. The higher TN values (0.12%) was recorded from lower position of woodland, whereas the highest OC (1.20%) was recorded from lower positions of conserved land. The highest CEC (55meq/100gr soil) was recorded from the lower position of woodland whereas the least value (45meq/100gr soil) was recorded from the upper position of non-conserved land. Soil chemical parameters (pH, EC, Av.P, OC, TN, CEC) and exchangeable cations (K, Ca, and Mg) were significantly increased from upper to lower position. In general, the soil properties in all land use types were improved from upper to lower landscape positions. Thus, working soil and water conservation practices for all land use types, particularly in the upper land scape positions, are suggested.