CHARACTERISTICS AND CLASSIFICATIONS OF SOILS LOCATED ON TWO TOPOSEQUENCES AT ILE OLUJI, ONDO-STATE

Abstract

The position of a soil on a toposequence affects its morphological, physical and chemical characteristics which in turn determine its productivity with or without fertilizer application. The objective of this study was to characterize, classify and compare soil located on two toposequences that have been formed on precambrian basement complex at Ile-oluji in Ondo State, Nigeria. Pedons were dug on each of the two identified slopes and sampled according to genetic horizon. The study revealed deep pedon in the upper slopes, deep to moderately deep at the middle slope, and shallow at the base of toposequence 1.Pedon 6 which is the base of toposequence 2 is the deepest. The soils were strongly to moderately acidic and exchangeable cations decrease with depth in all Pedons. The dominance of basic cations in the exchange complex is reflected by the soil medium to high percentage base saturation (59.8% to 70%). Total exchangeable bases decreased with depth in all pedons. Soil nitrogen and phosphorus was low corresponding with the low organic carbon content. Effective cation exchange capacity (ECEC) values ranged from 3.46 cmol/kg to 8.27cmol/kg and the values were highest in the ‘A’ horizons of all pedons. Pedon 1,2,4,5 and 6 classify in the great group KandiUdalfs (Sub group Rodic KandiUdalfs) in the USDA Taxonomy and Albeluvisols in the FAO Classification while Pedon 3 classify in the great group Udarent and Sub group Alfic udarents in the USDA Classification and Eutric fluvisols in the FAO Classification