Stabilization of Calcium by Surface Charge Variation in an Oxisol
1977
Munns, D. N. | Fox, R. L.
In the surface layer of a Ca-deficient, fine-textured Hawaiian Oxisol, concentrations of Ca in solution were poised against tendencies to increase with liming in the pH-range 5–6, and to decrease with dilution in the range of water content 0.35 to 2.0. Effects of lime and water content on the distribution of Ca between solid phase and solution were shown to be quantitatively consistent with effects of pH and ionic strength on exchange capacity. Relationships between soil pH, cation exchange capacity, and dissolved Ca were determined in soil samples taken from a field-liming trial. Effects of ionic strength on exchange capacity were determined by summation of adsorbed metal cations after equilibration of soil samples in different salt solutions. Effects of water content on cations in solution were determined by analysis of solutions centrifugally extracted at various water contents. The results help explain why Ca-deficiency may sometimes be corrected better by neutral Ca salts than by lime and why saturation-extract Ca may approximate soil-solution Ca adequately for diagnostic purposes.
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