Selected physico‐chemical characteristics of soils from the sub‐humid and semi‐arid zones of Nigeria

Abstract

Soil samples obtained from basement complex soils which spread across the major soil areas in northern Nigeria were analyzed for both physical and chemical properties. The soils are slightly acid. Acidity decreased with depth. The textural class ranged from sand in the semi‐arid areas to sandy clay loam in the southern part of the sub‐humid zone. Organic carbon content ranged from 0.17 to 1.5%, whereas nitrogen (N) levels ranged from 0.04 to 0.08% in the surface horizon. The soils have high base saturation indicating low Al3+concentration. The levels of available phosphorus (P) were inadequate for satisfactory plant growth, given a critical level of 15 mg kg‐1 was established for Nigerian soils. A significant correlation (r=0.63) was observed between pH and P on one hand and with clay content (r=0.47) on the other hand. The low values of the silt:silt + clay ratio, used as a weathering index indicated that the soils must have undergone advanced weathering. The magnitude of calcium:magnesium (Ca:Mg) ratio indicated that more calcium than magnesium was available in the soils. More iron than aluminum was extracted from soils by the dithionite‐citrate method. Soils from the sub‐humid zone had relatively higher levels of organic matter and total N than the semi‐arid areas. In the same vein, marginal higher values for sand and base saturation were found in soils from the semi‐arid areas than the sub‐humid zone.