Characterization and Taxonomic Classification of Some Basement Complex Soils in Kwara State

The soils of the Oyun Local Government Area of Kwara State were studied with the aim of characterizing and classifying them to provide the needed inputs into the Agricultural Transformation Agenda of the Government. Six soil mapping units were identified and designated YN1, YN2, YN3, YN4, YN5 and YN6. The soils were all formed on basement complex rocks, had deep weathered pedons and lateritic layers at depths less than 100 cm deep. Most of the soils were imperfectly to poorly-drained with sandy loam texture while structural aggregates were still poor to weak. The soil units were low in cation exchange capacity, basic cation (Ca, Mg, K), total nitrogen, available phosphorus and organic carbon. The soil units were low in available micronutrients Cu and Zn but high in Fe and Mn. The soil mapping units are therefore, low in their inherent fertility status. The classification of the soils mapping units of the survey areas shows that nearly all the mapping units were classified as Alfisols at the order level, indicating a fairly matured soils with well developed horizonation and fairly moderate base saturation. At the suborder level, they were mostly classified as Ustalf because of their ustic moisture regime. Soils on the narrow inland valley floors (YN1) however, classified as Entisols indicating a youthful soil development. The soils were mostly Luvisols and Lixisols at the group level in WRB while the Entisols were placed as Fluvisols and Cambisols.