Technical Abstract: Prediction of boron adsorption and transport has required detailed studies of B adsorption and subsequent determination of model parameters. In this study we tested a general regression model previously developed for predicting soil B surface complexation constants from easily measured soil chemical characteristics. The constant capacitance model, a chemical surface complexation model, was applied to B adsorption isotherms on 22 soils from the A and B horizons of 16 soil series from Oklahoma and Iowa. The measured chemical properties were surface area, organic carbon content, inorganic carbon content, and aluminum oxide content. The prediction equations were used to obtain values for B surface complexation constants thereby providing a completely independent evaluation of the ability of the constant capacitance model to describe B adsorption. The model was well able to predict B adsorption isotherms on the majority of the soils. The prediction equations developed from a set of soils primarily from California, were able to predict B adsorption on a set of soils from different parts of the country. This result suggests wide applicability of the previously developed model prediction equations for describing B adsorption both as a function of solution B concentration and solution pH.