Forms and Profile Distribution of Phosphorus in Soils formed on different Parent Materials in different Ecologies of Edo State, Nigeria.

Resumo

Forms and profile distribution of phosphorus in soils formed on different parent materials (cretaceous sediments, shale and quaternary alluvium) in different ecologies (Ekpoma, Ozalla and Illushi) of Edo State of Nigeria were investigated. Soil samples were collected from profile pits sunk on each parent material type. Total and organic phosphorus was determined by standard laboratory procedure while inorganic phosphorus forms by fractionation. Data obtained were analyzed using t-test and correlation analysis. Results showed that the total phosphorus ranged from 402 to 650 mg kg-1, 248 to 662 mg kg-1 and 88 to 345 mg kg-1 in soils of Ekpoma, Ozalla and Illushi with means of 498, 404 and 247 mg kg-1, respectively. Ozalla soils having higher values followed by Ekpoma soils while Illushi soils have lower values.The P forms showed no definite pattern of decrease with increased soil depth except for total P that decreased with increased soil depth in all the soils.The inorganic fractions of the soils occurred in the sequence of Fe-P > Al-P > Ca-P.The inactive residual P constituted 85.91% of the total P in Ekpoma soils, while Ozalla soils and Illushi soils constituted 76.35% and 80.19% of the totalP, respectively. There was a clear dominance of the inactive over the active forms of P, which partly explains the low available P in the soils and it also indicates that plants cultivated on these soils are not likely to obtain an adequate supply of P for good growth and development without P fertilizer application.