The Effect of Bulk Density on Emission Behavior of Soil at Microwave Frequencies

Abstract

Dielectric constant and dielectric loss (ε′ and ε″) of different soil samples with bulk densities varying from 1.3 to 2.0 gm/cm3 are determined at a single microwave frequency 9.78 GHz and at temperature 37.0°C. Different bulk densities of same soil are achieved by filling the wave guide cell with an equal volume but a different mass of soil. Further, ε′ and ε″ of these soil samples are also estimated by semiempirical model and compared with the experimental results. The values of ε′ and ε″ increase as bulk density of the soil increases. In view of microwave remote sensing, the Fresnel reflectivity of soil is computed from the knowledge of the complex dielectric constant and the surface boundary condition. Using Kirchhoff’s reciprocity theorem the microwave emissivity is estimated from Fresnel reflectivity of the surface. It is observed that the microwave emission from the soil surface inhibits as bulk density of soil increases. Further, the roughness of soil surface has been taken into consideration in the emissivity computation and observed that the emissivity increases with increasing roughness of the soil surface.

Global Mapping of Microwave Emissivity and Emitting Depth in Arid Areas Using GMI Observations

“…To extend the applicability of the derived dielectric properties to frequencies between 10 and 89 GHz, a simple parameterization of the imaginary part of the permittivity is proposed. $${{\epsilon}}_{\nu }^{{\prime\prime}}$$ has been described as an inverse function of the frequency for dry rocks (Ulaby et al., 1990), or with a Debye‐type model dependent on multiple parameters such as the sand fraction (Dobson et al., 1985; Gupta & Jangid, 2011; Peplinski et al., 1995), and soil moisture contents above 5%. For very dry soil, we suggest an empirical approach, only retaining the inverse relationship of $${{\epsilon}}_{\nu }^{{\prime\prime}}$$ with frequency: $$${{\epsilon}}_{\nu }^{{\prime\prime}}=a+\frac{b}{\nu },$$$ with a and b coefficients to represent the spatial variation of the dielectric properties.…”

Carbon sequestration in the bio-edaphic ecosystem of National Highway-27 in Guwahati, Assam, India

“…A vigorous soil needs air, water, and pore space for proficient root penetration and plant growth. If soil is compact or bulk density is too high, then plant roots will not propagate well, and hence yield will be reduced ( Gupta and Jangid, 2011 ). Thus, information on bulk density will assist in soil management and in future planning to enhance soil fertility by technological means ( Chaudhari et al., 2013 ).…”

Review and Assessment of Electromagnetic Wave Propagation in Sand and Dust Storms at Microwave and Millimeter Wave Bands --- Part I

“…At present, models of SD permittivity exist reflecting certain physical and structural properties (e.g., [11,15]). Most of these models only took bulk permittivity into consideration [28]. However, recent studies by [9] introduced scaled permittivity.…”

“…This technique however does not work well for low loss materials. [28,39] considered many of the reported dielectric constant values as inaccurate apparently due to the measurement techniques and the way the samples were collected and prepared. The work attempted to compile (from the literature) values believed to be the most accurate and reasonable.…”