ABSTRACT

Information on soil properties and distribution is critical for making decisions with regard to crop production and mitigating land degradations. This study was conducted to examine the effect of topography on soil properties along a toposequence in Ikpa River Basin in Akwa Ibom State, South Eastern, Nigeria. The toposequence was delineated into three physiographic units and a soil profile was established in each of the units. The profiles were described morphologically and soil samples collected from the identified horizons were analyzed for physical and chemical properties. The soils were examined and the influence of topography on their properties, pedogenesis and classification were evaluated. The study showed that landscape position, erosion and drainage significantly influenced variation in soil properties across the toposequence. The soils or the upper and middle slopes were well drained and deep compared with the poorly drained soils of the lower slope whose depth was limited by high water table at the depth of 90 cm. The particle-size distribution revealed dominance of sand fraction in the area (72.33 – 88.32 %). The soils were generally low (K⁺ and Na⁺) to medium (Ca²⁺ and Mg²⁺) in exchangeable bases. However, the soils were moderate in, organic carbon, effective cation exchangeable capacity, available P and high in base saturation. Topography influenced variation of soil types with their classification as Typic Psammentic Hapludults for soils on upper and middle slopes, whereas soils on the lower slope as Typic Endoaquults (USDA Soil Taxonomy).  The soils were correlated as Acrisols (upper and middle slopes) and Fluvisols (lower slope) in World Reference Base.