Determination of Dielectric Properties of Agricultural Soil

The efficiency of thermal treatment for the disinfection of soil with microwaves requires a knowledge of the dielectric properties. The dielectric constant ε′ and loss factor ε″ of irradiated material are basic parameters in the design of microwave applicators. This article analyses both parameters in several types of agricultural soils using a coaxial probe. The behaviour of the soil is determined when it is irradiated, and therefore the percentage of radiation that is absorbed, transmitted or reflected. Soils of several densities were evaluated at different moisture contents, and at a temperature of between 20 and 25 °C. The results show that significant differences exist between the dielectric properties of soils of different textures. The factor that has the most influence in each of these materials is moisture content. Adjustments have been made using multiple regression models which allow the calculation of ε′ and ε″ for the given conditions.