Adsorption and chemical extraction of phosphorus as a function of soil incubation time

Abstract

The objectives of this work were to evaluate the relationship between phosphate adsorption in different mineral soil constituents of the clay fraction to determine the P recovery rate by the Mehlich-1, Mehlich-3, Bray-1 and CaCl2 0.01 mol L-1 extractants as a function of incubation time of soil as well as to compare this rate with physical and chemical soil characteristics. In five soil samples five doses of P based on the maximum phosphate adsorption capacities (MPAC) of the soil, were applied, corresponding to 0, 0.2, 0.4, 0.8 and 1.0 level. The samples were incubated for 90, 60, 30, 15 and 0.5 days. The experiment consisted of a 5 × 4 × 5 factorial (five doses, four extractants and five different periods of incubation time) in five different soils, all distributed in blocks, with three replicates. The P content in soil was deter-mined by the Mehlich-1, Mehlich-3, Bray-1 and CaCl2 0.01 mol L-1 extractants. The soil characteristics that best correlated with the recovery rate of applied P were the remaining P (rem-P) and the MPAC. Soils high in gibbsite presented the highest P adsorption. Soils possessing high MPAC and the low rem-P presented higher reversibility for the non-labile P (residual P) for smaller time periods.