Crop growth response and dynamics of inorganic phosphorus fractions after application of reactive Arad phosphate rock in Oxisol with different land use histories.

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