Properties, genesis, classification, capability and sustainable management of soils from south-western Nigeria

Abstract

Soils derived from some parent materials in South-Western Nigeria covering 219,580 ha of land were mapped at a scale of 1:50,000 using a combination of conventional and remote sensing methods of soil survey. The aim is to generate detailed information on the properties, genesis and land characteristics of these soils for their sustainable use and management. Seven soil series were identified and classified (Kulfo series, Typic Paleudalf; Ibeshe series, Typic Rhodudalf; Idesan Series, Fluventic Eutrudept; Iweke Series, Typic Udipsamment; Alagba Series, Typic Haphudalf; Ondo Series, Typic Ferrudalf and Fago Series, Typic Plinthudult). Soils of Ondo and Fagbo series contain a lot of iron manganese concretions, quartz stones and gravels. The soils are very strongly acidic (4.50) to moderately acidic (5.70). The soils have moderately low inherent natural fertility with low exchange basic cations (Ca, Mg, K, Na), organic carbon, cation exchange capacity, total nitrogen but moderate to high micro-nutrients (Cu, Fe, Mn and Zn). Soils of the sedimentary origin (Alagba, Iweke, Idesan, Kulfo and Ibeshe) were observed to be more fertile and more variable in soil properties than those derived from the basement complex (Ondo and Fagbo series). Dominant pedogenic processes which influence the rate of soil development within the study area include hydrolytic weathering, lessivation, plinthization, pedoturbation, braunification, induration, leaching, erosion and colluvial deposition. The soils were classified into land capability classes. Only four (I, II, III and IV) out of the eight capability classes were encountered. Recommendations for sustainable use and management of these soils are discussed.