keywords: pedological properties, topography, precipitation, landuse
A pedological investigation was carried out on the soils on the foot of the Mambila plateau windward in the guinea savanna, north-east Nigeria. The soils of Ussa in Ussa local government area of Taraba was used for the study. Ussa was selected for the study based on the high amount of precipitation and its toposequence. Based on the criteria of USDA soil taxonomy, the soils were classified as Typic isohyperthermic kandihaplustults and this corresponds to Arenic Acrisol (WRB). Three land use pattern was used in the identification and delineation. The profile pits were sunk and samples were collected based on horizon differentiation. Most horizons had greater than 76% sand, 4.28% silt and 8.07% clay with a distinct clay bulge at the B horizons. The preponderance of sand is attributed to translocation of finer soil particles and the major textural class was sandy loam. The soils have reddish brown as the dominant hue (5YR5/3, 5YR7/6, 10YR6/8, 10R7/4). The bulk density was low with a corresponding high porosity. The soils had strong pH mean value 5.09, 5.06 and 5.18% for the oil palm, arable land and floodplain pedons respectively. Low OC mean values in all the profiles (6.4 g/kg, 4.0 g/kg and 2.8 g/kg for the oil palm, arable land and floodplain pedons respectively). The ECEC has the highest mean value (6.71 cmol/kg) at the oil palm landuse. The available phosphorus ranges from very low to low in all the profiles (3.55 mg/kg, 3.75 mg/kg and 2.61 mg/kg), the base saturation (%) very low (25.10%, 23.01% and 23.38%) with preponderance of Ca and Mg of the basic cation in the exchange site. The mineralogy of the soils was dominated by quartz and kaolinite. Single use of urea fertilizer will increase the chances of acid forming agents (H+). The use of N:P:K (20:10:10) fertilizer and use of integrated soil fertility/nutrient management is recommended.