Phosphorus adsorption in soils of the colombian coffee zone. Adsorción de fósforo en suelos de la zona cafetera de Colombia.

Understanding the phosphorus’ (P) dynamic in soils and the factors that determine its availability for plants proves essential in the efficient management of the nutrient, as well as its environmental impact. The aim of this study was to evaluate the capacity for P adsorption of representative soils of the Colombian coffee-producing region and its relationship with other edaphic properties. Using the adsorption isotherm technique, phosphate retention for soil samples from 14 municipalities classified as Andisols and Inceptisols, was determined. The Langmuir and Freundlich models were used to explain the capacity of soils to retain P and calculate the adsorbed fraction at a concentration of 0.2 mg.L–1 in the equilibrium solution; a criterion that was used in its classification. Phosphorous maximum fixation capacity varied between 118 y 3,333 mg.kg-1. Although both models satisfactorily explained the phenomenon under study, the Lagmuir model was selected, given that its parameters provide physical meaning. According to this model, samples from Antioquia and Tolima exhibited a very high fixation, those from Caldas and Cauca exhibited a high fixation, those from Caquetá, Casanare, Guajira, Huila, Meta and Santander a medium fixation, and those from de Magdalena, Norte de Santander, Nariño and Quindio low. A positive and significant correlation was found between P fixation capacity and the contents of organic matter and amorphous clays. Although Andisols retained a greater amount of P, the affinity degree for the element varied between these.