Mineralogical Composition and Distribution in Selected Floodplain Soils of Southeastern Nigeria: Implications for Arable Crop Production

Abstract

Floodplain soils are found on low-area of land where flood water periodically spreads when a river or stream overflow its banks. Floodplain soils of Mgbo-Abaja, Obokofia and Mbutu in Southeastern Nigeria formed under alluvium parent material were investigated and characterized in terms of their physical, chemical and mineralogical properties. Six profile pits (> 150 cm depths) were dug, two each in Mgbo-Abaja (Abakaliki), Obokofia (Egbema) and Mbutu (Owerrinta) study sites. The pits were geo-referenced using handheld GPS receiver, described and sampled from genetic horizons. Soil samples collected were air-dried, sieved and analyzed in the laboratory to determine their physico-chemical properties using standard methods, and mineralogical analysis using x-ray diffractometer. Results indicated that pedons were sandy in nature with low contents of organic carbon, pH, basic cations, cation exchange capacity and base saturation. Minerals in soils showed strong peak values at different intensities: Abakaliki site was dominated with quartz, zircon, magnetite and anatase with percentage abundance of 70%, 7%, 8% and 15% respectively; Egbema site recorded a percentage abundance of 69% and 31 % for quartz and microcline respectively; and Owerrinta site had 86%, 12% and 2% abundance in quartz, kaolinite and rutile respectively. Quartz minerals contribute to good soil structure, drainage and growing environment for crops. Zircon mineral (Mgbo-Abaja site) releases trace elements like zirconium which support various physiological processes in plants. Magnetite mineral (Mgbo-Abaja site) can be utilized for soil mapping and monitoring purposes, contributing indirectly to efficient soil management practices. Rutile and Anatase (Mbutu and Mgbo-Abaja sites respectively) can influence some soil properties such as water-holding capacity, nutrient retention, soil acidity and alkalinity which affect crop growth. Microcline (Obokofia site) which contains feldspar minerals releases K⁺ ions and can contribute to soil fertility, supporting crop productivity. Kaolinite (Mbutu site) has high water-holding capacity that aids in retaining moisture for plants during dry periods, but low in CEC and nutrient-holding capacity, which result in reduced nutrient availability for plants.