THE EFFECTS OF LAND USE AND DEPTH ON SOIL PROPERTIES AND QUALITY IN MAWULA WATERSHED, SOUTHWESTERN ETHIOPIA

Abstract

Soil chemical and physical properties of various agro-ecologies are affected mainly by nutrient loss due to changes in land use, and poor land management. The determination of this paper was carried out to study soil physical, chemical and quality properties of land uses and soil depths of Mawula watershed, southwestern Ethiopia. The study considered three lands uses (cultivated, grass, and forest) and two soil depths (0-20 cm 20-40 cm) replicated on purposefully selected three kebeles on the Belg (autumn) season. Eighteen composite soil samples were collected to study the soil physical and chemical properties. The result indicated on ANOVA that forest land recorded significantly (P ≤ 0.05) the highest mean value of clay contents, total porosity (TP),soil organic matter(SOM),total nitrogen(TN),Available phosphorus(Av.P), Available potassium (Av.K), cation exchange capacity (CEC) and exchangeable base; calcium, magnesium, potassium and sodium (Ca, Mg, K, Na).Cultivated land achieved significantly the highest on Sand content, bulk density (BD) electrical conductivity (EC), but the lowest value on clay contents, TP, SOM, TN, Av.P, Av.K, CEC, and exchangeable base (Ca, Mg, K, Na) while Grassland has a medium value obtained overhead properties and also recorded highest silt content, pH value. Furthermore, the finding presented that, sand, TP, SOM, TN Av.P, Exchangeable base (Ca, Mg and K) and CEC significantly (P ≤ 0.05) decrease with depth while clay content and BD significantly increase with depth. However, silt and EC non-significantly decreased from surface to subsurface whereas pH, C: N, Na and PBS increased with increase of soil depth. A soil quality index was affected by the interaction effect of land uses and soil depth. The result showed that, surface of forest land (0.86) was significantly higher than the adjacent land uses of sub surface of cultivated land grass land (0.44). Therefore, crop rotation, adding crop residue to the field, and applying organic fertilizer were recommended to increase the fertility status and improve the quality of farmed land in the watershed.