Uso de la isoterma de adsorción para evaluar requerimientos de fósforo, 1: Isotermas de adsorción de los suelos [Venezuela].

Abstract

The principal aim of this research work is to determine the phosphorus fertilizer requirements in some Venezuelan soils. The chosen soils were contrasting in both chemical and textural characteristics. The method consisted in determining, firstly the phosphorus adsorption isotherm (for each soil) and secondly, the P requirement of the plant crop under study, determined from pot or field experiments This first paper details the study performed on the chemical characteristics of six representative Venezuelan soils making emphasis in their P— adsorption behaviour It was found that six (6) days is a convenient period for the adsorption reactions to complete (equilibrate) and also that the reaction is temperature dependent: The well known Langnutir's isotherm model was found to adjust at the lower P additions (0-5 ppm P in equilibrium) On the other hand, the Temkin's model allotvs for the use of a wider P fertilizer treatments (until 12 ppm P in equilibrium). Phosphorus retendon in these soils is a function both, of Fe and Al "active" forms and of the textural characteristics.