Sodium-Calcium Exchange Behavior in Organic Soils1
- D. V. Naylor and
- Roy Overstreet2
The exchange complex of two organic soils from the Sacramento-San Joaquin delta of California was easily saturated with calcium. However, the Ca2+ of the calcium-saturated soil was difficult to replace with Na+ even when the calcium-saturated soils were leached with 1N NaCl. Exchange of the Ca2+ by Na+ was found to be reasonably stoichiometric and complete after extensive leaching of the calcium-saturated soils with the 1N NaCl solution. A large fraction of the adsorbed Ca2+ was extremely difficult to replace with Na+ when the soils were leached with large volumes of 0.01N NaCl.
The Ca-Na ion-exchange isotherms of the soils were determined through the use of Vanselow's and Gapon's ion-exchange equations. Vanselow's ion-exchange “constant” indicated an increased selectivity for Ca2+ over Na+ as the amount of exchangeable Na+ increased while Gapon's equation yielded a constant selectivity throughout the isotherms. Both equations suggested that the soils exhibit a very large selectivity for Ca2+ over Na+, especially as the amount of exchangeable sodium becomes appreciable.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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