Effect of Exchangeable Sodium on Some Soil Physical Properties

In a laboratory study the effect of exchangeable sodium (varying from 5 to 70%) on some physical properties of a dominantly illitic, alluvial sandy loam soil, was evaluated. With increasing exchangeable sodium percentage (ESP) moisture retention increased at soil-water suctions greater than about 0.2 atm while at lower suctions more moisture was held in soils of low ESP. Infiltration rate, soil-water storage, hydraulic conductivity and soil-water diffusivity underwent a sharp decrease when ESP was higher than about 15. Dispersion and displacement of dispersed particles is considered to be the chief mechanism responsible for observed reductions in the transmission characteristics. The depth to which the dispersed particles are displaced decreases with increasing dispersibility resulting from high ESP values.