Characterization and Classification of Soils of a Toposequence in a Derived Savannah Agroecological Zone of Nigeria

Soil properties are anisotropic in nature, hence the need to study soil associations and regional landscapes for sustainable nutrient management and soil profile is an important tool which can be utilized for this purpose.

The objectives of the study are to describe the morphology of the soils of the toposequence, determine their physical and chemical properties, classify them and make an appraisal of their agricultural potentials.

Three slope classes were considered and a total of three profile pits, one on each slope were studied and described in the field morphologically at Eleyin Farms Omu-Aran, Kwara State, Nigeria, which was a newly opened up plantation. Samples of soil were collected from the horizons of the profile pits. The soil samples were analyzed for their physical and chemical properties.

All the three pedons showed appreciable differences in physical, chemical, and morphological characteristics of the soils and their classifications were determined as guided by their characteristics. The textural classes were defined mainly by the sand compositions which decreased from the upper and middle slopes down to the bottom slope, and the clay compositions which increased progressively from the uppermost slope through the middle slope to the bottom slope. Silt compositions did not exhibit any particular pattern.

Thus, sand and clay compositions were more significant and relevant to the textural classification of the soils of the area than silt. The low nutrient status of the soils can be ameliorated by incorporation of organic or farm residues to increase the organic matter content of the soil, and also improve management practices and guided chemical fertilizer use. The soils of the area were classified as Typic Haplustalf (USDA), and Ferric Luvisol (FAO).