Fig. 4. Comparison of cation exchange capacity (CEC)-pH relationships determined by the modified silver-thiourea (AgTU) method (solid lines), the buffered AgTU method (broken lines) and the ion adsorption method (dotted lines). Data points presented are averages of four (modified AgTU method) or three (buffered AgTU and ion adsorption method) replicates. All regressions are significant at P 0.0001.