Geospatial modeling of soil erodibility for sustainable land management planning in Ethiopia

Abstract

Soil erosion is a serious environmental problem worldwide, with over 80% of Ethiopia’s land highly vulnerable to erosion. The Revised Universal Soil Loss Equation (RUSLE) is widely used to estimate soil erosion, and the soil erodibility factor (K-factor) is one of its key components. While past studies in Ethiopia have evaluated soil erodibility, they were mostly focused on small or local areas like watersheds, districts, etc. A national-scale assessment is missing but is important for better understanding and managing soil erosion in the country. This study estimated soil erodibility factors across Ethiopia using the RUSLE Nomograph and Erosion-Productivity Impact Calculatormodel methods, combined with Empirical Bayesian Kriging at a 250 m resolution. The Nomograph method provided more accurate K-factor estimates compared to observed data. We also developed indices, including the Clay Ratio (CR), Modified Clay Ratio (MCR), and Critical Level of Organic Matter (CLOM), to analyze their sensitivity to soil erodibility. Using the CLOM index, we produced a digital map showing the variation of erosion susceptibility across Ethiopia. The national average K-factor value for Ethiopia was estimated to be 0.04 t-ha-h/ha/MJ/mm. In addition, among soil types, Nitisols were the least susceptible to erosion, while Solonetz soils were the most vulnerable. This is the first study to map soil erodibility across Ethiopia nationally, providing valuable information for soil conservation and erosion management efforts. This study presents the first national-scale soil erodibility map for Ethiopia. K-factor estimated was using the widely used Nomograph and EPIC models. CLOM index correlated with soil erodibility under Ethiopian conditions. Soil erodibility factor values were quantified for major soil type in Ethiopia.