Abstract:The spatial and temporal variability of soil properties limits the determination of soil physical parameters in situ and in a dynamic way. In this paper the technique of Thermo-Time Domain Reflectometry (Thermo-TDR) is introduced to make measurements of a wide range of soil physical properties. We outline the theories of TDR technique for water content and electrical conductivity measurement, and heat-pulse technique for determination of volumetric heat capacity, thermal conductivity, and thermal diffusivity. Furthermore, the parameters of soil bulk density, air-filled porosity, and degree of saturation are derived from the theoretical relationship between heat capacity, bulk density, and water content.