PHOSPHORUS SORPTION AS INFLUENCED BY PH IN ORLU SOIL SERIES OF NIGERIAN INSTITUTE FOR OIL PALM RESEARCH (NIFOR) BENIN CITY.

Phosphorus (P) is an important element for plant growth and development, However, P availability is strongly influenced by pH in soils. Hence, this study aims at evaluating P sorption as influenced by pH. This study examined some physical and chemical properties of soil as well as in phosphorus sorption capacity at different pH levels. Soil samples were collected from orlu soil series in Nigeria Institute for Oil Palm Research (NIFOR). Some physical and chemical properties were analyzed using standard procedures in department of soil science and land management resources laboratory, university of Benin. while the influence of pH on sorption was determined by equilibrating the soils with P retention solution containing 1000 mg P L-1 as KH2PO4 adjusted to exactly pH 3.0, 4.6, 7.0 and 8.6 for 24 hours. The P remaining after equilibration was determined using colorimetrically by the nitric vanadomolybdate yellow method using the spectrophotometer at 466nm. The % P retention was calculated from the graph of absorbency against P retention of the standard solution.The result showed that some physical and chemical properties studied were within the normal range suitable for crop production. The result shows that % P sorption varied with depth and was strongly influenced by pH. The P sorption was least at the neutral pH range of 7.0 with a mean value of 12.90 and was highest at very low pH (pH 3) with a mean value of 26.50. It was also high at alkaline pH range (pH 8.6) with a mean value of 13.84 confirming the influence of pH on P sorption in line with several studies stated in literature All the data collected were subjected to statistical analysis using Analysis of Variance of GenStat Statistical Package and means were separated using Duncan Multiple Range Test of the same GenStat package. It is recommended that farmers in the study area should maintain a neutral pH to minimize P sorption.