Soil Vulnerability to Water Erosion in the Baobolong Watershed, Nioro du Rip, Senegal: A Soil Science and Principal Component Analysis Approach

Abstract

Agricultural sustainability has become a major challenge in West Africa due to soil degradation exacerbated by anthropogenic and climatic pressures. Water erosion causes considerable land loss on denuded soils and recently cleared slopes of the Nioro du Rip region in Senegal.  This soil study conducted in the Baobolong watershed aims to characterise the physical and chemical properties of soils in relation to their sensitivity to water erosion. Several soil sampling missions were organised in the Nioro du Rip area, and five (5) transects were developed. For physicochemical analyses, the granulometric analysis, carried out using the Robinson method, combines sieving (sandy fraction) and decantation (silt, clay). Principal component analysis (PCA) was applied to identify correlations between variables and highlight the factors determining the organisation and spatial dynamics of soils. The results show a predominance of loamy textures, low organic matter content, variable saturation levels, and high to very high erodibility (K > 0.45). PCA highlights four structuring factors (F1, F2, F3 and F4 with values 46.7%, 25.1%, 9.4%, and 7.2%, respectively), including organic matter decomposition and acidification. These data underscore the risks to the sustainability of local agricultural systems. The variability of soil profiles in terms of depth and physico-chemical properties is influenced by the topography, which determines water and erosion dynamics. The soils derive from a uniform parent material, clayey sandstone.