Pedogenesis and Classification of Soils on Contrasting Parent Materials in Taraba State, North East Nigeria: Filling a Taxonomic Gap

This study investigates pedogenic processes and provides systematic classification of soils developed on contrasting parent materials in Taraba State, located in Nigeria's North East geopolitical zone. Despite Taraba State's diverse geology and significant agricultural importance, systematic pedological characterisation and Soil Taxonomy classification of its soils remain largely absent from the published literature, creating a foundational knowledge gap for land use planning and fertility management. Using a toposequential soil survey design, eight pedons were excavated on granitic basement, metasedimentary schist, and alluvial parent materials in Gashaka, Sardauna, and Bali local government areas. Full morphological descriptions and horizon-by-horizon sampling were conducted. Laboratory analyses encompassed particle size distribution, bulk density, pH, organic carbon, total nitrogen, cation exchange capacity, exchangeable bases, aluminium, free iron and aluminium oxides, clay mineralogy by X-ray diffraction, and weathering index calculations. Soil classification was performed under both USDA Soil Taxonomy and the FAO World Reference Base. Findings revealed that granitic basement soils were predominantly Kanhapludults and Plinthudults, reflecting advanced ferralitisation and plinthite formation. Metasedimentary parent materials produced Typic DystruSoil Sciences with high silt content and moderate fertility. Alluvial soils were Fluventic EutruSoil Sciences with high base saturation and moderate-to-high agricultural potential. The study provides the first systematic Soil Taxonomy classification for Taraba State soils and identifies significant pedogenic contributions of parent material chemistry to fertility and classification outcomes. Keywords: pedogenesis, soil classification, parent material, Taraba State, Soil Taxonomy.