Unsaturated flow of different quality irrigation waters through clay, clay loam and silt loam soils and its dependence on soil and solution parameters

The effect of total electrolyte concentration (TEC) and sodium adsorption ratio (SAR) of irrigation water on unsaturated hydraulic properties, viz. unsaturated hydraulic conductivity, wetting front advancement and soil-water diffusivity of clay (Typic Haplustert), clay loam (Vertic Haplustept) and silt loam (Lithic Haplorthent) soil was studied in a laboratory experiment. Twenty-four types of irrigation waters, encompassing four TEC levels, viz. 5, 10, 20 and 50 me l−1 and six SAR levels, viz. 2.5, 5, 10, 15, 20 and 30 m mol1/2 l−1/2 were synthesised to equilibrate the soil samples using pure chloride salts of calcium, magnesium and sodium at Mg:Ca=1:2. Unsaturated hydraulic conductivity (Kθ), was determined both directly (by ‘inflow–outflow’ vertical infiltration method for water potentials of −5 and −10 kPa) and indirectly (from diffusivity functions and soil-water retention curves) in two different water potential ranges. Wetting front advancement and diffusivity (Dθ) were determined by the horizontal infiltration method.