Phosphorus forms in soils of Oban Hills, Akamkpa, Cross River State, Nigeria

W Ubi,Mw Ubi,Au Akpanidiok,O Ibor

doi:10.4314/gjass.v13i1.4

Abstract

Oban Hills is located at Akamkpa in the Southern Senatorial District of Cross River, State, Nigeria. Phosphorus (P)-rich soil from the Hills is expected to have an effect on retention and distribution in the highly acidic soils surrounding the area inundated for several years. Phosphorus forms in the soils of the Hills varied with the year of deposition with the highest fraction being Ca-P. The low soil pH in the Oban Hills soils suggests that Ca-P may exist in a partially dissolved form and will be the primary source of P for vegetations around the area. The cation exchange capacity andpH of surface material from the Hills suggest a dominance of primary minerals. Based on the amount of P available it seems that the Hills soils play a role in the overall P availability to the surrounding vegetation. A significant (P<O.05) decrease in HCI soluble P with depth was observed in the OB2 soil site, where the greatest amount of HCI-soluble P was found in the 0-15cm soil depth. The bicarbonate P varied with sites (OBI, OB2 and 0B3), and depth, but the OB3 had the highest value.KEYWORDS: Phosphorus, Soils, Oban Hills, P-fixation, P-distribution

Highlights

Soils derived from Oban Hills have been a rich source of nutrients for many agricultural crops; the major limitations of the soils are phosphorus (P) fixation, aluminum toxicity and high acidity (Holland et al, 1989)
Much work to investigate P forms present in soils of Oban Hills have not been done except the “Land Evaluation and Agricultural Recommendations” carried out by Holland et al (1989) for Cross River National Park, Oban Division
The P fractionation method used in this study enabled us to identify variations in predominant inorganic P pools including soluble surface-adsorbed, as well as P bound to Ca and Fe/Al in Oban Hills derived and resulting soils, which allowed us to determine P availability to the vegetation

Summary

Introduction

Soils derived from Oban Hills have been a rich source of nutrients for many agricultural crops; the major limitations of the soils are phosphorus (P) fixation, aluminum toxicity and high acidity (Holland et al, 1989). Soil P fractionation methods extract operationally defined P pools from various types of soils by sequentially removing them with different chemical reagents This method has been used as a tool to identify predominant inorganic P pools in soils, which include water-soluble, Al-P, Fe-P, occluded and Cabound P forms (Hedley et al, 1982; Maguire et al, 2000; Ubi et al, 2009). The P fractionation method used in this study enabled us to identify variations in predominant inorganic P pools including soluble surface-adsorbed, as well as P bound to Ca and Fe/Al in Oban Hills derived and resulting soils, which allowed us to determine P availability to the vegetation

Objectives

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Results

Conclusion