Characterisation and classification of valley-bottom soils in Southwestern Nigeria: Implications for land degradation neutrality

Abstract

Valley-bottom (hydromorphic) soils in southwestern Nigeria support vital ecosystem services but remain poorly characterised for sustainable use. This study examined nine pedons from three sites (Iwofin, Osuru, and Debjik) near Ogbomoso, Oyo State, to 1.5 m depth and analysed their morphological, physical, and chemical properties following FAO protocols. Soils were predominantly sandy (surface sand: 69.5 – 77.9 %), with bulk density 1.41 – 1.54 g cm⁻³ and porosity above 40 %, indicating minimal compaction. The soils were slightly acidic to near-neutral (pH 5.49 – 6.20), with low organic carbon (0.97 – 1.85 g kg⁻¹) and total nitrogen (0.11 – 0.20 g kg⁻¹). Available phosphorus and cation-exchange capacity were low to moderate, dominated by calcium. Principal component analysis identified organic carbon, clay, and available phosphorus as key fertility determinants. These results provide baseline data for land-use planning in Oyo State. Overall, low organic matter and nutrient reserves highlight the need for integrated soil fertility management (ISFM), organic-matter restoration, and conservation-based practices to enhance productivity and support Nigeria’s Land Degradation Neutrality targets.