Pedon-Scale Characterization and Classification of Soils at the Teaching and Research Farm, Nnamdi Azikiwe University, Awka, Nigeria

The Teaching and Research Farm of the Faculty of Agriculture, Nnamdi Azikiwe University, Awka, is a source of crop trials, teaching and soil science research, but the horizon-level information of its soils is lacking. This study characterized and provisionally classified three pedons (P1, P2 and P3) selected across the farm’s soil–landscape units. The profiles were described according to the Food and Agriculture Organization (FAO) guidelines and samples from each horizon were analysed for physical and chemical properties. The profile depths varied from 83 to 150 cm with the A–AB–Bt field-horizon sequences. The particle-size results indicated predominantly sandy-loam textures with the reported sand contents of 572–712 g kg⁻¹ and clay contents of 108–208 g kg⁻¹. However, the reported particle-size fractions for P1 Bt2 sum to 1,060 g kg⁻¹ and need to be verified. The bulk density varied from 1.19 to 1.76 Mg m⁻³, and pH in water from 5.44 to 6.10. Available phosphorus ranged from 0.96 to 4.27 mg kg⁻¹; the reported organic carbon and total nitrogen values and units need to be confirmed against the laboratory records. Effective cation exchange capacity ranged from 3.08 to 5.33 cmol(+) kg⁻¹, while ECEC-based base saturation was 65–84%, aluminum saturation 9.2–28.3%, and exchangeable sodium percentage below 4%. The low-chroma matrices and red mottles in the lower horizons of P1 and P3 suggest periodic redox conditions. Provisionally, P1 and P3 were considered possible Hapludults (Ultisols) and Acrisols in the World Reference Base (WRB), while P2 was considered an Inceptisol and Cambisol candidate. These placements are not definitive since the diagnostic-horizon criteria and classification-specific chemical data were not fully confirmed. The findings provide pedon-scale baseline information and identify priorities for verifying the soil data and assessing the nutrient, subsoil-strength and drainage constraints.