Modified Rayleigh Model in the Interpretation of Soil Moisture Data

Surface soil moisture is important to understand environmental systems and dielectric constant is a convenient physical parameter to describe this. Dielectric Mixing models relate the effective dielectric constant of a heterogeneous medium with the properties of constituent materials. The dielectric properties of the soil is known to have dependence on Soil moisture content along with other factors like texture, frequency, salinity etc. In this investigation, experimental data of Dielectric Constant of various types of soil has been taken at 1.4 GHz and 18 GHz to fit unknown parameters in modified Rayleigh mixing model. Calculation of Effective dielectric constant and emissivity of different types of soil has been carried out and using modified Debye formulation, spread in relaxation and relaxation frequency is also obtained. Effective dielectric constant increases with rise in volumetric Soil Moisture, while the emissivity decreases. Further the emissivity increases with the increase in Roughness parameter. Relaxation Frequency (fr) and spread of relaxation (α) are identified as microscopic parameters to characterize the soil texture along with volumetric moisture. These parameter values decreases with an increase in soil moisture. These data can be obtained in laboratory and field conditions and can be of interest to agricultural scientists.