Mineralogical Investigation of Some Imperfectly and Poorly Drained Soils of the Nigerian Northern Guinea Savanna Agroecology

This study aimed to investigate the mineralogy of soils with impaired drainage formed within the northern guinea savanna of Nigeria. Soil survey procedure was carried out to identify the two soil individuals (polypedon) namely: imperfectly drained soil (IDS) and poorly drained soil (PDS) that occupied 6,407.68ha (90.96%) and 636.82 ha(9.04%) respectively. In each soil individual, a repre- sentative soil profile pit was dug, described, and sampled from genetic horizons. Soil samples collected were prepared and the <2 μm fractions were subjected to laboratory mineralogical analysis. Evaluation of the soil depth and topography indicate IDS was deep (124 – 151 cm) and situated on nearly level (1 – 2 %) to gently sloping (3 – 7 %) ground on a mid-slope to lower slope position and PDS was also deep (142 – 147 cm) on the lower slope to the floodplain. Kaolinite dominated the clay-sized mineral in PDS. The dominance of kaolinite/kaolinite polymorphs indicates that the soils are mature and highly weathered. However, it was believed to have been brought about partly by erosional and depositional processes which contributed to the variation in mineral composition. The occur- rence and dominance of Zeolite in IDS were attributed to pedogenesis because of its polymorphic platy habit. The presence of Quartz in both soil individuals (IDS and PDS), though in low amount counts for its high resistance to weathering which is indicative of inheritance from the parent material (basement complex)