Pedogenic Forms of Iron and Manganese and Its Implication on Soil Genesis Over a Lithosequence in Nigeria

The citrate-bicarbonate-dithionite extractable iron and manganese oxides (Fed and Mnd), oxalate extractable iron and manganese oxides (Feox and Mnox), sodium pyrophosphate extractable iron and manganese oxides (Fep and Mnp), active iron and manganese oxide ratios (Feox/d and Mn ox/d) and Clay/dithionite iron ratio (clay/ Fed) were evaluated in soils derived from schist and older granite in two agroecological zones to evaluate the influence of parent materials on soil development and identify major pedogenic processes in the study area. Significant differences were observed in means of most of the properties studied between the parent materials except for means of Fed and Mn ox/d that were not significant. There were higher values of Fed, Feox, Fep, Mnd, Mnox and Mnp (2.276, 0.511, 0.350, 0.085, 0.017 and 0.016% respectively) in soils formed on schist. There was a correlation between the forms of iron and manganese with gravel, clay, pH and exchangeable cations. the major pedogenic processes in the soils are, co-translocation of Fe with clay by elluviation and illuviation, plinthization and co-migration of clay with Mnd. This study revealed that parent materials influence pedogenesis in the soils studied and the extent of pedogenesis varied on the lithosequence.