Elemental oxide evaluation of selected soils of varying lithologies in Akwa Ibom State, Southeastern Nigeria

Abstract

A study was carried out to investigate the mineralogical properties of selected soils of Akwa Ibom state with the objectives of identifying the elemental composition, extent of soil development, and the degree of weathering necessary for fertility evaluation and general soil
management. Soils formed from coastal plain sands, beach ridge sands, and alluvial deposits were chosen for the study. Two soil profiles were sited in each of the selected locations, and described using FAO guidelines for soil profile description. The samples were obtained based on their genetic horizons for laboratory analysis of physical and chemical properties using standard methods. In addition, analysis of elemental composition of the soils was determined by energy dispersive x-ray (EDX/EDS). Results showed that the coastal plain sands were dominated by sandy loam (SL) textures, beach ridge sands were dominated by sandy loam (SL), sand(S) and sandy clay loam (SCL), while the alluvial soils ranged from loamy sand (LS), sandy loam (SL) to sandy clay loam (SCL). The results showed that soils of coastal plain sands had mean values of 4.45% CO₂ and 1.49% F₂O, beach ridge sands had 1.73% F₂O and 12.65% Fe₂O₃ while the alluvial soils had 0.97% K₂O, 2.11% CO₂, 2.68% F₂O, 0.89% MgO, 0.07% CaO and 11.71% Fe₂O₃ in the B-horizons. The ‘immobile’ elements showed the highest mean concentration of SiO₂ in coastal plain sands (54.43%) while alluvial soils had the least mean value (40.36%). Comparatively, alluvial soils showed the highest mean concentration of Al₂O₃(14%) while soils of coastal plain sands reported the lowest mean  concentration (3.96%). Results of weathering indices also showed that Ruxton ratio differed among the three selected soils with different parent materials. Mean Ruxton ratio was highest in coastal plain sands (13.7%), followed by beach ridge sands (6.9%), while alluvial soils had the lowest (2.9%). The alluvial soils had the highest fertility status.