O.A.Orji1 and P.O Abam2
1Crop and Soil Science Department, University of Port Harcourt, Port Harcourt P.M.B.5323 Port Harcourt
2Crop/Soil Science Department, Rivers State University Nkpolu-Oruworukwo, Port Harcourt
Corresponding Author: O.A.Orji
Abstract:
The forms and status of Phosphorus in soils derived from varied parent materials in Cross River State were examined. The study involved soil sampling at 0-15cm depth from five locations representative of soils formed from coastal plain sand (CPS), shale (SH), basement complex rocks (BCR) sandstone (SS) and basaltic rocks (BAR). The soils were analyzed for the various forms of P and routine soil properties using standard procedures. The results obtained indicated that total P varied widely due to the nature of parent materials and ranged from mean value of 76.8mg/kg in sandstone to mean value of 290.9mg/kg in shale with the order of relationship being SH > BAR > BCR > CPS >SS. Organic–P varied widely ranging from mean value of 22. 8 mg/kg in sandstone to 99.7mg/kg in shale and in the order SS < CPS < BCR <BAR < SH. The relative abundance of the active P forms were in the order of Fe–P > Al–P > Ca–P in all the soils except those formed from shale where Ca–P was more abundant. Same trend in distribution was observed for total active and total inorganic–P forms being in the order SS < CPS < BCR < BAR < SH. Available P extracted by the two methods correlated strongly with the other P forms. Bray P–2 method removed larger amount of P than Bray P-1 and the soils varied remarkable in their available P contents. Available P indices of 8mg/kg (Bray-1) and 15mg/kg (Bray–2) showed that soils derived from shale and basaltic rocks were high and well endowed with Plant available P whereas the soils formed on coastal plain sand, basement complex rocks and sandstones were relatively low and deficient in P content and would certainly require P fertilization for optimum crop production. The levels of P in these soils informed the need for proper understanding of the various forms of P to enhance soil P management and judicious fertilizer Usage.
Keywords: Phosphorus forms, Soils, Parent materials, Cross River State, Nigeria.