Classification and Suitability Assessment of Soils on a Fine Grained Biotite Schist Toposequence for Maize and Cassava Production in Ife Area, Southwestern Nigeria
The study characterized and assessed the suitability for production of maize and cassava, of soils on a toposequence underlain by fine grained biotite schist in Ife Area and developed management plans with a view to providing information on the suitability of the soils for maize and cassava production in the area. The taxonomic classes of the soils were also indicated. The established toposequence in the study area was delineated into five (5) different physiographic units and a total of five soil profile pits were established, described and sampled at each unit. The soil samples collected from each genetic horizons were subjected to routine analyses. Taxonomic and suitability classification of the soils were carried out. Results showed that the colour, depth and texture of the soils varied in response to changes in slope position and drainage condition. Soil colour ranged from reddish brown to dusky red (5YR 3/2-2.5YR 3/2) in the surface and yellowish red (5YR 4/8) to reddish yellow (7.5YR 6/6) in the subsoil. Texturally, the soils were sandy clay loam in the surface to sandy clay in the subsoil. The solum was moderately acidic to neutral (5.20 – 6.70) at the surface and strongly acidic to moderately acidic (4.40 – 5.70) in the sub soils. They are characterized by low exchangeable bases which were in the order Ca> Mg> Na> K irrespective of slope position with low to moderate organic matter. The effective cation exchange capacity of the soils was positively correlated with pH (0.52**), organic carbon (0.96**) and available P (0.64**). Bedrock thin section confirmed that the soils were derived from the weathering of the fine grained biotite gneisses and mica schist. Soils along the toposequemce were described as ultisols (Order), ustult suborder and as Typic Kanhaplustults (Family level) soil taxonomy. The FAO-UNESCO soil legend equates all the soils under consideration as Luvisols. The results of the actual (a) suitability evaluation showed that the soils are not presently suitable (NS) for commercial cultivation of maize, and cassava in their current condition. However, potential suitability of the soils were ranked moderately suitable (S2) for maize and soils of Olorunda and Oba series were rated marginally suitable for cassava while others still remain (NS) for cassava.This study, therefore, provided evidence for the need to adopt different management practices to suit each soil type at the different physiographic positions as indicated by the agronomic constraints to ensure sustainable use of the soil resources.
