Modeling the displacement of resident soluble salt during infiltration

We present two analytical models to assess the displacement of the initial saline soil solution during infiltration. The models are extensions of the analytical infiltration solutions of Morel-Seytoux and Khanji (1974) and Broadbridge and White (1988). We then introduce simple experimental methods with the tension infiltrometer to measure the parameters of the two models in the field. A single measurement of sorptivity is needed to determine the free parameter, C, in the Broadbridge and White solution, and the viscous correction factor, β, in the Morel-Seytoux and Khanji solution. The tension infiltrometer method, in conjunction with the analytical models, provided simple and inexpensive means to predict the leaching of soil-solution as required for saline soils. The tension infiltrometer was simple to operate and measurements were performed at the surface to minimize installation time and soil disturbance. The analytical models contained parameters with precise physical meaning and need modest amounts of computation time. The narrow range of 0 to -15 cm of soil-water pressure, in which infiltration rates were measured with the infiltrometer, appeared sufficient for modeling the displacement of soil-solution. This was attributed to the rapid decrease of hydraulic conductivity with water pressure, which was manifested by a short macroscopic capillary length for the field soils tested.