Evaluation of Soil Oxide Mineralogy in Different Bedrock Lithologies in the Southern Guinea Savannah of Nigeria

Agriculture has very important social and economic footprint in Africa. Its soil resource is however threatened by degradation resulting from mismanagement, due to lack of knowledge on important soil functional properties such as mineralogy, which impact many soil processes. This study was therefore conducted to access variations in soil oxide mineralogy in soils formed from differing bedrock lithologies. Soil sampling was carried out on soils from three different bedrock types; basement complex rocks, recent alluvium, and Nupe sandstone in Kwara state, southern Guinea Savannah of Nigeria. Data was subjected to analysis of variance to determine significant differences in treatment means (p<0.05), and correlation analysis was performed to determine relationships between measured variables. Elemental oxide composition of soils from the different bedrock materials were found to be significantly different. Soils from all three bedrock types had very high amounts of silica by mass (>80 %). The highest mean percentage of 90.59 was recorded in recent alluvium-derived samples, while the least value of 80.75 % was recorded in basement complex-derived samples. Aluminum and iron oxides were the most saturating metal oxides in all the bedrock types, and significantly higher values of 5.65 % and 2.71 % for Al2O3 and Fe2O3 respectively were recorded in basement complex-derived soils. Dissimilar trends of mineral oxide relationships were observed in soils from the different lithologies, which are likely a result of bedrock characteristic, environmental and hydrologic factors. The relationships established between oxide minerals in this study could serve as a foundation for subsequent investigations into mineral interactions in the soils