ELECTRIC CHARGE CHARACTERISTICS OF ANDO A, AND BURIED A, HORIZON SOILS

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Abstract
Summary: The electric charge characteristics of four Ando soils (A 1 and μA 1 ) and a Chernozemic soil (Ap) were studied by measuring retention of NH 4 + and Cl – at different pH values and NH 4 Cl concentrations. No positive charge appeared in the Ando soils at pH values 5 to 8.5 except for one containing allophane and imogolite. The magnitude of their negative charge (CEC; meq/l00g soil) was dependent on pH and NH 4 Cl concentration (C; N) as represented by a regression equation: log CEC = a pH + b log C + c , where the values of a and b were 0.113–0.342 and 0.101–0.315, respectively. Unlike the Chernozemic soil, Ando soils containing allophane, imogolite, and/or 2:1–2:1:1 layer silicate intergrades and humus showed a marked reduction of cation retention as pH decreased from 7 to 5. This was attributed to the charge characteristics of the clay minerals and to the carboxyl groups in humus being blocked by Al and Fe.