PHOSPHORUS SORPTION CAPACITY OF KULFO SOIL SERIES IN NIGERIA INSTITUTE FOR OIL PALM RESEARCH (NIFOR), BENIN CITY, EDO STATE

ABSTRACT

Phosphorus (P) is one of the important macronutrients needed by plants. However, sorption results in reduced availability of P for plant uptake. The study was conducted on twelve (12) samples collected from four (4) soil depths: 0-30, 30-60, 60-90, and 90-120 cm, in three (3) replications from the Kulfo soil series of the Nigeria Institute for Oil Palm Research (NIFOR). Physical and chemical properties were determined following standard procedures. The physical properties indicated that the soil's textural class was sandy loam for all depths, except at 0-30 cm, where it was Loamy Sand. The chemical properties of the soils revealed that they were acidic, with a mean pH value of 4.71. Organic carbon (OC) and Total Nitrogen (N) decreased significantly with increasing soil depth. Available P ranged from 0.37 to 0.40 mg kg-1 , with a mean value of 0.39 mg kg-1 . Potassium levels ranged from 0.24 to 0.35 cmolkg-1, calcium from 0.45 to 0.81 cmolkg-1 , magnesium from 0.25 to 0.28 cmolkg-1 , and sodium from 0.08 to 0.09 cmolkg-1 , respectively. The cation exchange capacity (CEC) and Base saturation (BS) did not increase with increasing soil depth and had mean values of 1.29 cmolkg-1 and 67.33%, respectively. The P sorption capacity was determined by equilibrating the samples in thirty (30) ml of 0.01M calcium chloride (Cacl2) containing various concentrations of P as KH2PO4 for six (6) days at room temperature. The model that best expressed P sorption capacities was determined by fitting the adsorption data to the Freundlich, Langmuir, and Temkin models.