Topographic positions and land use impacted soil properties along Humbo Larena-Ofa Sere toposequence, Southern Ethiopia

Understanding the dynamics and distribution of soil characteristics as influenced by landscape features and land use is critical for making decisions with regards to crop production and other types of proper land use. A field study was conducted to evaluate the relationship between topography position, land use and soil properties along the toposequence of Humbo Larena - Ofa Sere in Wolayita zone, Southern Ethiopia. Five slope classes were considered and a total of five pedons, one on each slope class, were opened and described at the study area. Soil samples collected from identified horizons of each pedon were analyzed for physicochemical properties. Additionally, random surface soil samples (0-20 cm) were collected from adjacent cultivated and grassland soils within a 100 m radius of each pedon; and three composites were made for each slope class. The pedons showed variability in physical, chemical and morphological characteristics of the soils. Field as well as laboratory determinations revealed the dominance of clay fraction in the soils. The existence of buried horizons with abrupt textural and sharp color changes showed the occurrence of lithological discontinuity in the pedon opened at depression. The available P content was higher in cultivated soils, whereas grassland soils had more organic carbon (OC), exchangeable bases and cation exchange capacity (CEC). Two soil types; Rhodic Alisols (Clayic) and Pellic Vertisols (Grumic) were identified in the area. Generally, slope and land use influenced soil properties, suggesting the need for different management practices for varying slope gradients and land uses for sustainable agricultural production. Key words: Toposequence, physicochemical properties, land use, pedon, slope gradient, landscape position, soil classification.