A comparative study of four methods used for the extraction of soil phosphorus, is presented. The methods were: a) IAC method, based on the extraction of, 5cm³ of soil with 50ml of 0.05N H2SO4; b) a modified Bray I method, based on the extraction of 2.5cm³ of soil with 50m1 of a solution 0.03N in NH4F and 0.025N in HCl; c) Olsen's method, based on the extraction of 2.5cm³ of soil with 50ml of 0.5N NaHCO3 solution at pH 8.5; d) an anion exchange resin method based on the extraction of 5cm³ of soil with 2.5cm³ of an anion exchange resin contained in a polyester netting bag, by shaking in 50ml water. For each method, the correlation coefficients between soil phosphorus and the response to phosphorus fertilization of 16 field experiments of cotton and 16 field experiments of corn were, respectively, 0.683, 0.650, 0.391 and 0.802, indicating the superiority of the anion-exchange resin method for the assessment of soil phosphorus availability.