MODELING THE DISPLACEMENT OF RESIDENT SOLUBLE SALT DURING INFILTRATION

We present two analytical models to assess the displacement of the ini tial saline soil solution during infiltration. The models are extensio ns of the analytical infiltration solutions of Morel-Seytoux and Khanj i (1974) and Broadbridge and White (1988). We then introduce simple ex perimental methods with the tension infiltrometer to measure the param eters of the two models in the field. A single measurement of sorptivi ty is needed to determine the free parameter, C, in the Broadbridge an d White solution, and the viscous correction factor, beta, in the More l-Seytoux and Khanji solution. The tension infiltrometer method, in co njunction 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 measurement s 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 narr ow range of 0 to -15 cm of soil-water pressure, in which infiltration rates were measured with the infiltrometer, appeared sufficient for mo deling the displacement of soil-solution. This was attributed to the r apid decrease of hydraulic conductivity with water pressure, which was manifested by a short macroscopic capillary length for the field soil s tested.