Electric charge characteristics of horizons of Ando (B) and Red‐Yellow B soils and weathered pumices

Abstract

Summary The electric charge characteristics of five Ando (B) and two Red‐Yellow B horizon soils and two weathered pumices were studied by measuring the retention of NH 4 + and Cl − at different pH values and NH 4 Cl concentrations. The magnitude of their negative charge (CEC; meq/100g) was dependent on pH and NH 4 Cl concentration (C; m ) as represented by a regression equation: log CEC = a pH + b log C + c. The values of the coefficient a (0.017 to 0.342), b (0.031 to 0.274) and c (1.41 to − 1.26) were correlated and depended on the kind of clay minerals present. A similar equation: log AEC = a ’ pH + b ’ log C + c ’ was also found for the positive charge in the Ando soils, but there was little difference in the values of a ’(−0.204 to −0.251), b ’(0.181 to 0.253) and c ’(2.06 to 2.46) between the soils. It was shown that the equations generally hold for soils with constant and/or variable charges and describe adsorption equilibria in which NH 4 + and H + , and Cl − and OH − compete for cation‐ and anionexchange sites, respectively. The significance and utility of the coefficients is discussed.