Inorganic phosphorus fractions extracted by sodium dithionite-citrate-bicarbonate and determined using the malachite green method

Phosphorus (P) fractionation is a common tool used in studies on soil P dynamics.However, the P fraction extracted by sodium dithionite-citrate-bicarbonate (DCB), occluded in iron oxides (P-occluded), is difficult to quantify.This study presents an alternative and simpler method for the quantification of the P-occluded fraction extracted by DCB.Samples were collected from a clayey Oxisol at a depth of 0-0.2 m.The extraction method followed the procedure described by Zhang and Kovar and malachite green method was used for determination.The malachite green method produced satisfactory quantification results, and it revealed a pattern that represents extract P concentrations according to the absorbance level.The method is suitable for simple determinations of P occluded in extracts of DCB.