Differences in sodication and desodication processes influenced by type of clay minerals and clay contents.

The processes of sodication and desodication in soil influences agricultural productivity. We explored sodication and desodication processes in montmorillonite and illite with varying ratios of clay contents in 5% and 25 % on sodium adsorption ratios (SAR) of 7, 13, and 20 of equilibrated solution with 10 mmolc L-1. The sodication and desodication processes were observed to vary considerably, depending on the type of clay, clay content, and equilibrated solution. Sodication and desodication processes were different even for the same clay under similar conditions. The differences in clay sodication based on SAR of equilibrated solution were observed, and it was found that sodication progressed comparatively more rapid in illite than in montmorillonite. The desodication processes varied according to the type of clay and clay content. In montmorillonite, desodication progressed comparatively better at low clay content than at high clay content. In contrast, it progressed more rapid at high clay content than at low clay content in illite. However, desodication processes in illite with low clay content had similar tendencies as SAR of an equilibrated solution. As a result, the Gapon equilibrium constant was different for clay sodication and desodication processes even in the same clay mineral and clay content. The clay sodication and desodication processes as well as final exchangeable sodium percentage values were affected not only by SAR of the equilibrated solution but by the type of clay minerals and clay contents as well. [ABSTRACT FROM AUTHOR]