Evaluation of methods for quantifying bioavailable phosphorus in a ferralsol from Cuba

As part of a research program related to enhance the agronomic effectiveness of P fertilizer, in particular phosphate rock, several methods to assess P availability of phosphate fertilizers were evaluated. Soil samples from pot experiments and a long-term field experiment in a Ferralsol from Ciego de Avila, Cuba, were analyzed using 32P isotopic exchange kinetic method and five chemical methods (Oniani, Bray 1, Olsen, Mehlich 2 and resin-P). Oniani and Bray 1 methods were good descriptors of available phosphorus (P) in soil when water-soluble P fertilizers were used. However, they only provided a static estimation of plant-available P. All the chemical methods used in this paper to evaluate P availability in a Ferralsol amended with Trinidad de Guedes phosphate rocks did not perform well because less than 10% of the P extracted was bioavailable. The 32P isotopic exchange kinetic method provided more reliable and accurate information of various parameters describing soil P status better than the soil P testing methods studied. (author)