Electromagnetic simulations for salinity index error estimation

Soil salinity index (SI) is a measure of salt concentration in soil water. The salinity index is calculated as a partial derivative of the soil bulk electrical conductivity (EC) with respect to the bulk dielectric permittivity (DP). The paper focused on the impact of different sensitivity zones for measured both EC and DP on the salinity index determination accuracy. For this purpose, a set of finite difference time domain (FDTD) simulations was prepared. The simulations were carried out on the model of a reflectometric probe consisting of three parallel rods inserted into a modelled material of simulated DP and EC. The combinations of stratified distributions of DP and EC were tested. An experimental verification of the simulation results on selected cases was performed. The results showed that the electromagnetic simulations can provide useful data to improve accuracy of the determination of soil SI.