Sesquioxides Distribution of Soils of Contrasting Land Units in Egbema, Southeastern, Nigeria
Sesquioxides provide information about several physicochemical properties of the soil including the age, drainage condition, ion retention amongst others. Duplicate soil samples were collected from three depths (0-15, 15-30 and 30-45 cm) of three land units (natural levee, floodplain and upland) in Egbema, southeastern, Nigeria. and analyzed for dithionate ( d ) and oxalate ( ox ) Fe, Al and Mn. Also the Fe d , Al d , Mn d , Fe ox , Al ox and Mn ox were correlated with selected soil properties. Soil Fe d , Al d and Mn d contents ranged from 7800-20400 and 2200-21900 mg kg -1 , 200-300 and 100-400 mg kg -1 and12000- 20000 and 6000-18100 mg kg -1 while Fe ox , Al ox and Mn ox ranged from 10000-20000 and 10100-16600 mg kg -1 , 100-200 and 100- 300 mg kg -1 and 600-1200 and 10000-14000 mg kg -1 in the top and sub soils respectively. Whereas, dithionate extractable Al and Mn  were higher than the oxalate extractible, the reverse was the case for Fe  indicating the prevalence of Fe in the amorphous highly reactive fraction. Active Fe, Al and Mn ranged from 0.98-1.28 and 0.55-4.90, 0.33-0.67 and 0.50-2.00 and 0.30-1.00 and 0.56-1.83 in the top and sub soils respectively indicating that their reactivity was stronger in the sub than the top soil. Mean active Fe was higher than the threshold values of 0.54 signifying that the soils are young and poorly drained with the youthfulness and low drainage conditions degreasing as floodplain > natural levee > upland. Soil properties especially sand, silt, clay, silt/clay ratio, TN, OM, P, Ca, K, Mg, Na, H, ECEC and % BS affected soil sesquioxide concentrations. In general, the soils may support intensive production of such crops as rice that tolerates waterlogging and could also retain large amounts of toxic materials or other pollutants from crude oil pollution into insoluble and non available forms due to their high reactivity. Keywords: Sesquioxides, Distribution, Soils, Land units and Nigeria