PHOSPHORUS SORPTION CHARACTERISTICS OF SOME SOILS OF THE RUBBER BELT OF NIGERIA

The phosphorus-sorption capacity of 30 soils from th Rubber Belt of Nigeria were evaluated. The method used involved equilibrating 3 g soil in 30 mL 0.01 M CaCl2 containing various levels of phosphorus (P) at room temperature. From the P-isotherm curve, the standard P-requirement (SPR) of the soil was determined. The values vary from low to medium and range from 10.5 mug/g soil to 153 mug/g soil. The langmuir equation was applied to the data from which the P-adsorption maximum was calculated. The values were fairly high and range from 125 mug/g soil to 750 mug/g soil. The standard P-requirement correlated significantly with the oxides of iron (Fe) and aluminum (Al), organic carbon, and clay content, while the adsorption capacity correlated significantly with the oxides of Fe and Al.