Average concentration of soluble salts in leached soils inferred from the convective–dispersive equation

Abstract

The convective-dispersive, or advective-dis- persive, equation (CDE) has long been the model of choice for solute transport in soils. Using the average concentra- tion of soluble salts in soil profile to evaluate changes in salinity due to irrigation can be beneficial when spatial variability of soil salinity at selected depths is larger than spatial variability of soil salinity in the layer encompassing these depths, and when soil salinity is evaluated with electric conductivity measurements that give layer-average rather than depth-specific salinity values. The objective of this work was to present analytical solutions of the CDE that express the average soluble salt content in soil profile as the function of time, water flux, and solute dispersion parameter. The solutions were developed for both semiin- finite and finite domain and implemented in a computer code. Examples are presented of using these solutions to develop a nomogram for the dispersion coefficient esti- mation and to evaluate the applicability of the semiinfinite domain solution to soil monolith leaching experiments. In cases when the CDE application is justified, the analysis of the salt leaching based on the average salt concentrations in soil profile provides estimates of the effective salt dis- persion parameter useful in land evaluation and soil