Samples of 30 soils were taken with the objective of characterizing the Capacity Factor of Phosphorus (CFP) and its relation with several properties of soils of Entre Ríos, Argentina. Isotherms of adsorption and a quick test of P adsorption were estimated. Langmuir and Freundlich equations described the adsorption phenomenon satisfactorily. The maximum adsorption capacity varied between 46 and 716 mg kg-1 of P in the soil, considering that the soils analyzed have from medium to low CFP. The adsorption capacity of P increased with clay content and wasn't affected by the soil's organic carbon concentration. The quick adsorption test permitted the characterization of the buffer capacity of soils and the estimate of its maximum adsorption capacity of P.
phosphorus; buffer capacity; clay; isotherms of adsorption; remaining-P; organic carbon