Equivalent salt solution series have been previously defined as solutions with combinations of sodium absorption ratio (
SAR) and electrolyte concentration (
Ec) producing the same extent of clay swelling in a given soil. The present study shows that there is a high (r
2>0.96) positive correlation between log
Ec and log
SAR of equivalent salt solutions series, in the equation: where a
1 and b
1 are constants for each equivalent salt solution series for a given soil. Log a
1 could also be represented as a linear function of b
1 resulting in the equation: where
a2 and
b2 are constants for a given soil. Solving this equation using any given value of
b1 yields the combinations of
SAR and
Ec which make up each equivalent salt solution series for a given soil. The relationship between log a
1 and
b2 for three soils from western United States, namely Waukena, Pachappa and Grangeville, was similar, with their combined data having a
r2 value of 0.96. This indicated that a single set of equivalent salt solution series values could be used for these three soils which have different clay contents and clay mineralogy. Prediction of hydraulic conductivity decreases with
Ec reduction at given values of
SAR in red-brown and alluvial soils from southern Tasmania, using the equivalent salt solution series values for Waukena soil, showed similar patterns to measured values and also to those predicted using the equivalent salt solution values applicable to the respective Tasmanian soils. Thus, available data indicate that the same set of equivalent salt series could be applied to the five soils studied. If further testing shows that a single set of equivalent salt solutions values could be applied to all or large groups of soils, this would facilitate the application of the equivalent salt solution concept to predict salt solution flow in the field.
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