ASSESSMENT OF DITHIONITE AND OXALATE EXTRACTABLE IRON AND ALUMINIUM OXIDES IN SOILS OF IDO-OSI LOCAL GOVERNMENT AREA OF EKITI STATE

Abstract

The nature and content of sesquioxides has become a good tool in making predictions of the pedogenic processes and physicochemical properties of the soils. The study was aimed at investigating the forms, content and distribution of Iron and Aluminium oxides within the horizons in soils of Ido-Osi Local Government Area of Ekiti State. Ten profile pits were dug at the study site. Soils samples was collected from pedogenic horizons and analysed for morphological, physical and chemical properties. The samples was also analyzed for dithionite (d) and oxalate (o) Fe and Al oxides. Also, Fed. Ald, Feo and Alo were correlated with selected soil properties. The soils were generally low in sesquioxides and vary with depth with sub soils higher than top soils in all the pedons. The soils had higher values of Fed than other sesquioxides (Feo, Ald and Alo) indicating that these soils exist in crystalline form. Fed, feo, Ald and Alo ranged in value from 37.04 – 374.07 mg kg-1, 4.56 – 337.11 mg kg-1, 9.33 – 99.00 mg kg-1 and 0.75 – 68.25 mg kg-1. However, their distribution is independent of clay migration as evidenced by the non significant correlation (p≤0.01) between Fed and clay (r = 0.201). All forms of Al in the soils are low especially the oxalate extractable form compared to the dithionite extractable forms. Active Fe (Feo/Fed), Fed/clay as well as silt/clay ratios indicated the soils are moderately weathered, poorly drained and young with low degree of weathering suggesting that the soils may still have some weatherable minerals with some of the nutrients locked up in the parent materials. In general, the soils could sustain intensive agriculture or crop cultivation due to its youthfulness but require liming and organic matter to reduce nutrient sorption and adaptable to poor drainage condition. Keywords: Sesquioxides, Dithionite, Oxalate, pedogenesis.