Soil texture often varies dramatically in both vertical and horizontal directions in field situations and affects the amount of B adsorbed and B movement. Boron adsorption on 15 soil samples (Lillis soil series: very-fine, smectitic thermic Halic Haploxerert) constituting 5 depths of each of three sites from the Broadview Water District in the western San Joaquin Valley of California was investigated as a function of solution pH (5-11). Boron adsorption increased with increasing solution pH, reached an adsorption maximum around pH 9, and decreased with further increases in solution pH. The constant capacitance model was able to describe B adsorption on the soil samples as a function of solution pH by simultaneously optimizing three surface complexation constants. The model was able to predict B adsorption using surface complexation constants calculated from easily measured chemical parameters using a regression prediction equation approach. The model was also able to predict B adsorption at all of the depths using the surface complexation constants predicted with the chemical properties of one of the surface depths and a surface area value calculated from clay content. Both modeling approaches were well able to predict the B adsorption behavior with the greatest deviation being about 40% in a couple of cases. These results are very encouraging, suggesting that for a particular soil series, B adsorption for various sites and depths in a field can be predicted using only clay content and the chemical information from a different site in the same field. Incorporation of the prediction equations into chemical speciation-transport models will allow simulation of soil solution B concentrations both spatially and vertically under diverse environmental and agricultural conditions.