Phosphate Sorption in Oxisols in Paraíba State, Brazil, Classified as Solution Equilibrium Phosphorus

Abstract: Aiming to evaluate the phosphorus adsorption in Oxisols with phosphorus remaining classified using the Langmuir isotherm, a study was developed in the laboratory at Federal University of Campina Grande, PB, with samples of the surface layer (0-20 cm) of three Oxisols of the State of Paraíba, differentiating among these the classification of the remaining P-values. The phosphorus levels for adjusting the isotherm were defined based on the remaining P-values. To assess the maximum P adsorption capacity data from P adsorbed and equilibrium concentrations of the solutions were adjusted Langmuir isotherm. This isotherm model could satisfactorily describe the adsorption of phosphorus in soils. The Oxisol sample with high P-rem was the highest value of maximum P adsorption capacity. The maximum P adsorption capacity was correlated with CEC and Ki for the samples classified as P-rem medium and high, respectively. Key words: Langmuir; Isotherm; Tropical soils INTRODUCTION and these interactions are known as adsorption, sorption The Brazilian Oxisols soils are weathered, very friable, Phosphorus adsorption is the phenomenon by which well structured and chemically poor [1]. The clay fraction P soluble forms, through covalent or electrostatic bonds of weathered Oxisols consists of a predominantly andprecipitation, with the formation of insoluble kaolinitic mineralogy, containing hematite, goethite compounds, they become unavailable to plants