Abstract
The forms and distribution of phosphorus in selected soils formed over different parent materials in Abia State of Nigeria were investigated. Total P varied widely ranging from 175.6 to 1252.45 mg / kg with overall mean of 450.68 mg/ kg. Ajata soils having higher values while Amakama have lower values. The organic P also varied widely ranging from 31.03 to 127.71 mg /kg with a mean value of 61.0 and 92.91 mg/ kg respectively. About 40% of the Total P in the surface horizon (Ap) of the fine-textured soils (Ajata ) are in organic P form while the coarse-textured soils ( Amakama ) 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. The occluded P and Fe-P comprise more than 84% of the total inorganic P. The content of Ca-P and Al-P were very low (<16% of the total inorganic P). The active inorganic P constitutes between 18 and 38% of the total P. There is high content of Al-P in the lower horizons of the Ajata soil. Available P is low with values ranging from 4-21 mg/ kg with a mean value of 11.59 mg /kg. The surface horizon (Ap) contains more available P than the subsurface soil horizons. The multiple correlation analysis revealed that total P correlated negatively with sand and positively with clay, exchangeable Ca, occluded P, organic P, Ca-P, Fe-P. Organic P correlated positively with Fe-P, Al-P and total P. Ca-P correlated negatively with sand and positively with organic carbon, exchangeable Ca, Al-P and total P. Fe-P correlated positively with organic P, Al-P and total P. Al-P correlated positively with Fe-P, Ca-P and organic P. The occluded P correlated positively with clay and exchangeable Ca and negatively with sand and pH.