Effects of landscape positions on soil physicochemical properties at Shenkolla Watershed, South Central Ethiopia

Abstract Background Understanding the effects of landscape positions on soil physicochemical properties is crucial for improving the soil productivity and to ensure the environmental sustainability. Three land use types forest land, grazing land and cultivated land all within upper, middle and lower landscape positions were selected to determine the effects of landscape positions, land use types and their interaction effects on soil physicochemical properties. Twenty seven soil samples were collected from lower landscape, middle landscape and upper landscape positions at the depth of 0–20 cm in nine replications. In addition, undisturbed soil samples were taken using core sampler from each land use type under upper, middle and lower landscape positions for the ascertainment of bulk density and water retentive capacity. The analysis of variance (ANOVA) was applied to determine variations in soil parameters among landscape positions and land use types. A Generalized Linear Models (GLMs) analysis was conducted to determine the influence of independent (fixed) factors, on the soil properties (response variables). Treatment means comparison was determined using the Least Significant Difference (LSD) at 0.05 level of significances. Results The result indicated that among the soil properties sand (p < 0.001), silt (p < 0.001), clay (p < 0.001), bulk density (p < 0.01), water holding capacity at FC (p < 0.001), water retention at PWP (p < 0.01), Available water content (AWC) (p < 0.01), soil reaction (pH) (p < 0.05), Soil organic carbon (SOC%) (p < 0.01), Total nitrogen (TN%) (p < 0.01), available phosphorus (p < 0.05) and CEC (p < 0.001) have shown a significant variation among the landscape categories. Similarly, variation of sand (p < 0.001), silt (p < 0.001), clay (p < 0.001), bulk density (p < 0.01), water holding capacity at FC (p < 0.001), water retention at PWP (p < 0.001), Available water content (AWC) (p < 0.01), soil reaction (pH) (p < 0.01), SOC (p < 0.01), TN (p < 0.001) available phosphorus (AP) (p < 0.001) and CEC (p < 0.001) were also statistically significant among the land use types. Moreover, lower landscape position and forest land had high mean value of SOC, TN, AP, CEC, EB (exchangeable bases), and available micronutrients, whereas upper landscape position and intensively cultivated land had low mean value of SOC, TN, AP, CEC, EB (exchangeable bases), and available micronutrients. Conclusion Landscape positions, land use types and interaction effects of landscape position and land use types (LSP * LU) significantly affected soil properties. Soil with best quality was found in lower landscape position and forest land, while less quality of soil was found in upper landscape position and cultivated land. Thus, efforts should be made to improve the quality of soil under upper landscape position and cultivated land using biological and physical soil conservation measures.