Salts Transport under Ponded Infiltration

Abstract

Two soils were used for salts leaching measurements under ponded infiltration, these were sampled from ridge in a greenhouse. One is light clay (A-soil) and the other is fine sandy loam (B-Soil).
When infiltration was terminated, soil column was segmented and then, water content and electric conductivity (EC) by 1: 5 dilution water extraction method was measured. The measured EC denotes the absolute salts per unit weight of soil, and salts concentration in soil solution is defined as EC is divided by water content.
A-Soil contains 27% clay and aggregate well than B-Soil, then A-Soil was not leached as well as B-Soil. So, the mobile-immobile water model was used to simulate the movement of salts under ponded infiltration for A, B-Soil.
In the model, the diffusional mass transfer coefficient is defined as follows. The concentration of mobile water at the soil surface approaches to that of ponded water with time. So, it is possible to replace the concentration of mobile water with that of ponded water in the immobile water diffusion equation for a long period of time. Applying the relative concentration ratio data at large infiltration time to the solution of this diffusion equation, the value of mass transfer coefficient divided by immobile water is obtained. Then, the mass transfer coefficient is determined by assuming the volumetric immobile water content (θ_im).
Assuming some θ_im in calculations, and found the suitable value which corresponded with measured data. By this method, good agreement between measured data and calculated results were obatined.