Solute dispersion in unsaturated heterogeneous soil at field scale: II. Applications.

The model for nonadsorbed solute spread by vertical steady-state flow of water in a heterogeneous field soil, developed in Part I, is applied to a Panoche soil with properties which have been investigated previously. Average solute concentration profiles as functions of depth and time are computed for various surface rates of infiltration. The average concentration over a layer extending from the soil surface to a given depth ia also computed. It is shown that the concentration profile extends over a mixing zone which is much larger than that predicted by a conventional diffusion-diffraction (dispersion) equation in a homogeneous fictitious field, and that the latter lacks practical significance for prediction of solute spread in the field. The implications of the results for the leaching of saline field soil and crop yield estimates as they are influenced by rate of surface recharge and its uniformity are also discussed. - Authors