Phosphorus sorption characteristics of some selected soil of the Nigerian Guinea Savanna

Abstract

This study evaluated soil samples from the Nigerian guinea savanna areas of Minna, Mokwa and Ankpa for their Phosphorus (P) sorption characteristics. The samples were equilibrated in 30 ml of 0.01M CaCl2 containing various amounts of P as KH2PO4 to give 0, 25, 50, 100, 200, 400, 800 and 1000µg L-1 P for six days at room temperature. Some soil properties as well as P sorption characteristics were studied in the samples. The adsorption isotherm of the samples showed different curves for samples of each soil series. It was evident from the curves that rates of P adsorption increased with increased concentrations of P, but at a certain level of higher concentration, the level of P became almost constant and had no more capacity to adsorb P. P adsorption capacity decreased in the following order Ankpa > Mokwa > Minna. The relative capacity of each soil sample to adsorb P was significantly and positively correlated with the soil’s clay content (r =0.81*), exchangeable acidity (r= 0.96**) and pH (r = 0.98**) but negatively correlated with the soil’s organic carbon content (r = -0.96**). The study showed that Ankpa soil required more P fertilization than the other soil samples for plant growth. Management practices involving the use of organic materials and liming as a basis for P sorption reduction will be useful for crop production in Nigeria especially in the southern guinea savanna agro ecological region.