Evaluation of surface soil quality and land suitability for agricultural soils affected by soil erosion

Abstract Globally, soil erosion is an important environmental factor affecting most agricultural lands, particularly dryland areas where vegetation cover is limited. This study, based on two assessments, was aimed at addressing the physical impact of soil erosion in dryland areas of Kebbi State, Nigeria. Soil erosion was assessed from the visual appearance of different erosion types and their resulting deposition patterns. In the first assessment, six types of soil erosion were evaluated: sheet, rill, gully, winnowing, mass-movement and dry-mechanical. These six types of soil erosion have slight, moderate or severe degrees of impact. Additionally, eight different shapes of rill and gully erosion were classified based on their physical appearance and the nature of their surface soil textures: C, I, J, S, U, V, X and Y. The V, U and Y categories described gully erosion under a uniform sand-silt soil texture, whereas the C, I, J, S and X categories described rill erosion under a sandy loam soil texture. In the second assessment, erosion was classified according to its category and degree of impact for soil quality and land suitability descriptions under the proposed specific visual soil erosion approach (VSEA). The physical soil quality classes Sq1, Sq2, Sq3, and Sq4 or Sq5 describe the surface soil conditions of the study sites at very slight, slight, moderate and highly moderate or severe degrees of impact, respectively. Ls1, Ls2, Ls3, Ls4 and Ls5 are the land suitability classes of good land, moderately good land, poorly good land, very poor land and bad land, respectively. Erosion significantly affected the potential productivity of agricultural soils (226 cm to 555 cm width and 116 cm to 213 cm depth) in the study area. However, important social factors such as poverty, overgrazing, lack of management skills, corruption and poor environmental government policy likely contributed significantly to the initiation and occurrence of surface soil erosion at the affected sites. It was very clear that the physical surface soil was damaged and that sustainable management was necessary.