Displacement Front Under Ponded Leaching

The leaching of tile-drained soils by ponding water on the soil surface is examined both experimentally and theoretically. A method of analyzing the movement of the displacement front (demarcation between saline soil water and fresh leaching water) is presented. The method is based on piston-type displacement of the saline soil water by the added leaching water. In this initial analysis the presence of precipitated salts, hydrostatic dispersion and soil-chemical reactions are ignored. The experimental results obtained on a 15 × 6 × 3 foot tank show satisfactory agreement to the theoretical results obtained by solving Kirkham's equation for the ponded water case. The results indicate that ponded leaching is inefficient in removing salts midway between the drains. Intermittent leaching by applying excessive amounts of irrigation water should be more efficient in controlling the soil salinity.