P status and sorption capacities of some native rangeland soils in northern Nigeria

Abstract

A study was conducted to determine the phosphorus (P) status of some soils carrying native pastures in northern Nigeria. Sorption capacities and forms of P in these soils were also studied. Consequently, soils developed from basement complex were obtained from nine locations in the zone for the study. Total P and available P contents of these soils were low. Available P ranged from 4.18 to 9.65 mg kg' while total P ranged from 133 to 235 mg kg ' with a mean of 187.8 mg kg '. Organic P accounted for about 7.65 to 21.8% of the total P. The relative abundance of the P forms was in the order; Residual P> Organic P> Fe-P>Ca-P > AI-P. There was a clear dominance of the inactive over the active forms, which partly explains the low available P in the soils. The sorption of added P varied with the soils, and was generally high. The P sorption capacity was positively related to the clay content (r= 0.71, P< 0.05) and Fe20 3 content (r— 0.70, P= 0.05). The low contents of total and available P in these soils is an indication that plants growing on these soils are not likely to obtain an adequate supply of P for good growth and development without P fertilizer application.