Some aspects of the cation status of soil moisture

Summary

In a previous paper it was shown that the equilibrium between the soil and its solution phase only remained undisturbed over the field range of moisture content but became disturbed once this range was exceeded. Values of pK−1/2p(Ca+Mg) increased with dilution. Equilibration studies with water and calcium chloride solutions (0.002–0.10M) showed that there was an increasing release of potassium from the soil into the soil solution with increasing solution/soil ratios and with increasing strengths of the calcium chloride-equilibrating solutions. Potassium was released in amounts in considerable excess of the exchangeable-potassium value and this value was also exceeded at decreasing solution/soil ratios for increasing concentrations of calcium chloride-equilibrating solutions. The interpretation given to these results is that because of the low exchangeable-potassium and exchange-capacity values, ‘excessive’ dilution or a relatively low concentration of divalent ions would cause a depletion of exchangeable potassium from the soil-exchange complex, and result in a release of potassium from intralayer sites of the illite mineral of the soil.

The possibility of such a release was strongly suggested by X-ray data whilst it was also shown that the release was from the illite of the silt fraction and not the clay fraction.