PHOSPHORUS ADSORPTION CHARACTERISTICS IN ALAGBA SOIL SERIES UNDER OIL PALM CULTIVATION

The study investigated phosphorus (P) adsorption characteristics in Alagba soil series under oil palm cultivation in Edo State. Soil samples were collected from four (0-30, 30-60, 60-90, and 90-120 cm) depths in three replicates, P sorption was analyzed by varying P concentration (20-100 mg P/kg) and contact time (5-1800 minutes) at constant temperature. The amount of P adsorbed was determined by difference after equilibration, and data were modeled using Freundlich and Pseudo-second order kinetics models respectively. Results showed that P adsorption increased with increasing P concentration and contact time, and was lowest in the topsoil (0-30 cm), possibly due to higher organic carbon and lower clay content at the top soil. Freundlich adsorption capacity (a) ranged from 28.18 to 45.71 mg kg⁻¹, and intensity (n) from 1.98 to 2.75 L kg⁻¹. The pseudo-second order rate constant (K₂) was lowest at 60–90 cm (2.76×10⁻⁴ mg kg⁻¹ min⁻¹) and highest at 90–120 cm (6.6×10⁻⁴ mg kg⁻¹ min⁻¹). Average coefficient of determination (R2) values of 0.767 and 0.972 obtained for Freundlich model and pseudo-second order kinetic model respectively indicates strong model fit to the adsorption data. This study offers improved P management practices in Alagba soil series under oil palm cultivation.