Dielectric constant and dielectric loss ( and ) 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, and of these soil samples are also estimated by semiempirical model and compared with the experimental results. The values of and 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. 1. Introduction Soil compaction or high bulk density of soil is important field of research due to agricultural importance. Soil compaction is the main form of soil degradation which alters the extent and configuration of the pore space. It can have adverse effects upon plants by increasing field saturated hydraulic conductivity, mechanical impedance to the growth of roots. In compacted layers, water, nutrients, and airflow towards the plant roots are also restricted. These restrictions may reduce the crop growth and, subsequently, the yield. There are various reasons associated with the increase in bulk density of arable soils classified as natural and anthropogenic. Conventional tillage practice and the use of heavy machinery and vehicular traffic on farmlands are important reasons for increasing bulk density of agricultural soil. The increasing bulk density of soil affects the dielectric properties of dry and moist soil [1, 2]. Different studies [3–7] predict that the dielectric parameters of soil at microwave frequencies are the function of various properties of soil such as texture, moisture, bulk density, temperature, and salinity. The physical properties of the soil like texture and structure influence the amount of pore space and the distribution of pore space within soil matrix. Thus, pore space and bulk density significantly affect the dielectric properties of the moist soil. In the present investigations, we have determined experimentally the
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