Phosphorus adsorption after drainage in two soil classes
The lowland soils, seasonally flooded for rice cultivation, feature alternate oxidation and reduction conditions, which determines intense modifications in the soil mineral solid phase and in the dynamics of highly reactive elements, such as phosphorus. This study aimed to evaluate the effect of drainage of two lowland soils after a flooding period on the maximum phosphorus adsorption capacity. The experiment was conducted in a greenhouse, the system factor was composed of two levels: 1) flooded soils for 63 days followed by drainage and after the humidity remained at 16 % by 184 days; 2) soil moisture maintained with 16% throughout the trial period. Samples were collected from the surface layer of two lowland soils. The determination of the maximum phosphorus adsorption capacity was made by the adsorption isotherms of adjustment according to the Langmuir model. The behavior of the maximum phosphorus adsorption capacity after soil drainage was different for both evaluated soil classes. An immediate reduction of maximum phosphorus adsorption capacity was seen after draining in the in the case of Albaqualf, while for Argiaquolls there was a tendency to maintain higher values of maximum phosphorus adsorption capacity after drainage, with subsequent reduction.