Abstract

Adsorbed or precipitated phosphorus can be susceptible to dissolution depending upon environmental conditions. This work evaluated both the partitioning and availability of the inorganic forms of P bound to Al, Fe and Ca in samples of a clayey Dystrophic Red Latosol (Oxisol) (DRL) with different land use history, fertilized with Arad reactive natural phosphate in Goias State, Brazil. The inorganic fractions of Al-P, Fe-P and Ca-P and the contents of Mehlich-1, ion-exchange resin, citric acid and Olsen extracted available P were determined in DRL. Plants grown in soil previously cultivated produce more beans than plants grown in soil not previously cultivated. The fractions Al-P and Fe-P represent the main inorganic forms in clayey DRL, being phosphorus availability closely related with the fraction Al-P. The distributions of the inorganic fractions of P in the soil fertilized with reactive phosphate were Fe-P = 45%, Al-P = 40% and Ca-P = 15%. The phosphorus content determined by alkaline extraction (Olsen Method) was closely related to levels of Al-P and Fe-P. On other hand, the concentrations determined by extracting acids (Mehlich-1 and citric acid) were more related to the Ca-P fraction. Fe-P and Al-P inorganic forms stocked over time with successive fertilizations in Oxisol with a history of cultivation in no-tillage may return to soil solution and provide the nutrient demand of plants.

Key words: Cerrado soil, phosphorus fertilization, phosphorus fractionation, inorganic phosphorus.