Profile Distribution of Crystalline and Amorphous Sesquioxides in Talc Overburden Soils of Southern Guinea Savanna Ecology in Nigeria

The stage of development of soils developed over talc overburden in two locations (Ejiba and Odo- Ogbe) within the Southern Guinea Savanna Agro-ecology of Kogi State, Nigeria, were evaluated using the dithionite and oxalate extractable Fe, Al oxides and the ratios of silt: clay and silt: silt +clay of the soils. Soil samples collected from the pedogenic horizons of nine profile pits dug in the two sites were analyzed using standard procedures. The soils had higher values of dithionite- extractable Fe and Al oxides (Fed, Ald) than oxalate- extractable forms (Feo, Alo), indicating that these soils had a higher content of the crystalline forms of these sesquioxides. The pattern of profile distribution of the sesquioxides and clay-sized particles were similar, resulting in a significant correlation (P<0.5) between Fed and clay content of the soils (r = 0.736 for Ejiba and 0.533 for Odo-Ogbe). The plinthite (Fe-Mn concretions) content of the soils at the first location (Ejiba) was significantly (P<0.01) correlated with the Fed (r = 0.537). The ratio of Feo/Fed, as well as the pedogenic Fe oxide content of the soils, indicated that the soils were at an advanced stage of development. There were, however, conflicting results in the evaluation of the stage of development of the soils using the silt: clay and silt: silt + clay ratios. While the silt: clay ratio indicated a low to moderate stage of development, the silt: silt + clay indicated an advanced stage of soil development in agreement with the Feo/Fed ratio and pedogenic Fe content of the soils. It was concluded that using the Feo/ Fed, silt: silt + clay ratios, as well as the pedogenic Fe oxide content of the soils, gave a better evaluation of the stage of soil development.