COMPARAISON DE DIFFERENTES METHODES D’EXTRACTION DU P ASSIMILABLE EN RELATION AVEC LES PROPRIETES CHIMIQUES ET PHYSIQUES DES SOLS DU QUEBEC

The objective of this study was to compare different available-P extracting methods on 83 Quebec soils. The alkaline Olsen’s method and five acid chemical extractants (Bray-1, Bray-2, new Mehlich, North Carolina double acid DA-4 and DA-10) were compared with each other and with two anion-exchange resin methods. The ratio of P-HCl/P-DAF of Mehlich was used to identify the group of soils with predominant P-Ca forms . Within this soil group, the Bray-2, DA-4 and DA-10 methods extracted more P and they were less correlated with all the other methods (r = 0.01 to 0.48*). The Bray-1 and Mehlich methods showed good relationships with Olsen, F−- and HCO3−-form resin methods (r = 0.80** to 0.89**) for this soil group, with the exception that Bray-1 solution was more affected by the presence of free carbonates. In the soil group containing more than 0.6% oxalate-Al, the Bray-1, Bray-2 and DA-10 methods extracted more P than the Mehlich, DA-4 or Olsen methods. The F−-form exchange resin extracted more P than that in...