Salt Accumulation in Soil-Root System

Abstract

Salt accumulation process associated with water uptake by plant roots is numerically solved by using the method of characteristics for solving convection-dispersion equation and the implicit finite difference method for solving Richards' equation. Root water uptake under a saline condition is assumed to be expressed by the root contact model of Herkelrath et al.(1977). The laboratory experiments are performed under a controlled-environment to test the validity of the proposed numerical method. Experimental results show that the transpiration rate under saline water irrigation decreases compared with that under freshwater irrigation. The calculated profiles of soil water content and salt concentration are in good agreement with the measured data. The numerical methods are also applied to the computation of the salt accumulation process due to the water uptake from the saline water fixed at the bottom boundary. It is demonstrated that the numerically predicted salt accumulation process agrees well with the experimental one and, that the shape of salt concentration profile is quite similar to that of root density profile.