AUTHOR: OHAERI, JOHN EMEKA (MSc)
DEPARTMENT: SOIL SCIENCE AND TECHNOLOGY
AFFILIATION: FEDERAL UNIVERSITY OF TECHNOLOGY OWERRI
The forms and distribution of phosphorus in selected soils formed over different parent materials in Southeastern Nigeria were investigated. The parent material of the soils are Coastal Plain Sands, Shale, Cretaceous Sandstone, Olivine Basalt, and Crystalline Basement Complex Rock respectively. The locations are Amakama Olokoro, Ajata Ibeku (Abia State), Ogoja, Otiri Ikom and Atimaka Yala Ikom (Cross River State). Representative soil profile pits were sunk in each of the five selected locations guided by the differences in their parent materials of their soils. The morphological properties of the soils were described after which soil samples were collected from each demarcated horizon. The samples were analysed for various forms of phosphorus and other physical and chemical properties of the soil such as particles size distribution, pH, organic carbon total nitrogen exchangeable Ca, Mg, K, Na, Al3+, and H+. Total P varied widely ranging from 175.6 to 1252 mg / kg with overall mean of 387.6 mg/ kg. Ajata and Ikom Red soils having higher values while Amakama and Ogoja have lower values. The organic P also varied widely ranging from 31.03 to 136.49 mg /kg with a mean value of 86.06 mg/ kg. The soils rank in the sequence of Ikom Grey> Ajata> Ikom Red > Ogoja> Amakama. About 40% of the Total P in the surface horizon (Ap) of the fine-textured soils (Ajata and Ikom Red) are in organic P form while the coarse-textured soils (Ogoja, Amakama and Ikom grey soils) have a very low (< 20%) organic P contribution to total P. The inorganic fractions of the soils occurred in the sequence of occluded P> Fe-P> Al-P> Ca-P. The occluded P constitutes between 26 and 68% of the total P in the various soils and 40 to 80% of the total inorganic P.
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