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

  • Rafael Silva Guedes Universidade Federal Rural da Amazônia
  • Antonio Rodrigues Fernandes Universidade Federal Rural da Amazônia
  • Luís Reynaldo Feracciú Alleoni Universidade de São Paulo
  • Marcos Yassuo Kamogawa Universidade de São Paulo
  • Marina Colzato Universidade de São Paulo


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.


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