Characterization and Classification of Soils Along Three Toposequences in Njikoka Area, Anambra State, Nigeria

Abstract

The study aimed to characterize and classify soils in the Njikoka Area of Anambra State, Nigeria. Three toposequences (TA, TB, and TC) from three different communities: Abagana, Nimo and Enugu-ukwu were selected and divided into upper (US), middle (MS), and lower (LS) slopes using a Digital Elevation Model (DEM). Nine pedons were described following FAO guidelines, and 64 samples were collected for analysis. The soils were well-drained, with predominant dark reddish brown and reddish brown horizons. Soil structure varied from weak fine granular to moderately medium angular and subangular blocky structures, while texture varied due to variations in sand, silt, and clay fractions. Soil acidity ranged from extremely acidic to slightly acidic. Organic matter, total nitrogen, available phosphorus, and exchangeable bases were generally low to very low. Potassium content ranged from very low to moderate, while exchangeable acidity, base saturation, and cation exchange capacity (CEC) varied from very low to high. The trend in chemical fertility was MS > US > LS for TA, US > MS > LS for TB, and LS > MS > US for TC soils. Based on the USDA soil classification, TA soils were identified as Typic Hapludults (US), Typic Kandiudults (MS), and Aquic Arenic Hapludults (LS). TB soils were classified as Grossarenic Kandiudualf (US) and Typic Kandiudults (MS and LS), while TC soils were categorized as Vertic Hapludults (US), Grossarenic Hapludults (MS), and Grossarenic Kandiudults (LS).