Effect of Solution Composition on Soil Hydraulic Conductivity

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Abstract
Decreases in hydraulic conductivity with decreasing electrolyte concentration and increasing sodium adsorption ratio (SAR) of the percolating solution were assessed for seven soils of varying clay mineralogy. The decreases were particularly pronounced for soils high in 2:1 layer‐silicates, with the most labile hydraulic conductivities being exhibited by those soils containing the most montmorillonite. A soil containing considerable amorphous material was much more stable then the average, and a soil high in kaolinite and sesquioxides was virtually insensitive to variations in solution composition. No property of the solution alone was sufficient to characterize the response of the soils to a given solution, though expression of results in terms of the exchangeable sodium percentage (ESP) of the soil and the total salt concentration of the ambient solution produced more nearly similar curves for soils of similar clay mineralogy. The soils commonly demonstrated rather pronounced hydraulic conductivity decreases in the ESP range of 20 to 35 at salt concentrations of 3 to 50 meq/liter. The decreases were largely irreversible upon the reapplication of high salt or high Ca solutions to the soil, except for those soils containing greater than 10% montmorillonite on a whole‐soil basis.

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