Characterization and Taxonomic Classification of Soils in Onigambari Forest Reserve South Western Nigeria

A soil survey of Onigambari forest reserve in Oyo State, Nigeria was carried out. Three soil mapping units Established-Teak-Plantation (ETP), Natural-Forest (NF) and Farm-Land (FL) were identified with observation base on vegetative pattern. Morphological properties of the study area show that the soil unit ETP is deep and texture ranges from loamy-sand at the surface to sandy clay loam in the subsurface. The soil unit NFand FL is not deep due to presence of hard pan but the texture ranges from sandy-loam to sandy-clay and loamy-sand to sandy-clay respectively. Physical properties of the soils showed the bulk density of the soils to be moderately good for growing plant with high porosity. The soils chemical properties indicate that the pH value of the soils in ETP, NF and FL are slightly acidic and organic-matter was very low in the soils of ETP compared to NF and FL soils. The total-nitrogen values of the soils in the area changed irregularly with depth and values ranged from 0.028 to 0.1g kg-1 in ETP, 0.05 to 0.25g kg-1 in NF, the value ranged from 0.03 to 0.26 g kg-1 in FL. 0.03 to 0.26 g kg-1. According to USDA soil Taxonomy system, all the profiles pits in the study area showed distinguishing characteristics of the order Alfisols, therefore the soils are classified as Alfisols. Profile in the Established-Teak-Plantation is classified as Typic isohyperthermic paleustalfs, Profiles Natural-Forest and Farm-Land with petro-plinthic material within 100cm of the soil surface qualified as plinthic isohyperthermic paleustalfs.