A method for studying soil-structure characteristics in three dimensions using millimeter and sub-millimeter (THz) is described. The method is effective down to the root zone. This is the critical zones that affect agricultural quality, with an emphasis on obtaining data regarding water content, salinity and particle size.

Soil water and salinity contents are currently monitored by conservative methods of sampling and laboratory testing. In addition in recent years, the task has been performed by a combination of hyperspectral remote sensing to map the surface and ground-penetrating tools to map the subsoil. Measuring changes in moisture content in the soil profile resulting from various precipitation regimes using the current methods is cumbersome, expensive and time-consuming. Consequently, the obtained data are incomplete. In addition, the current remote-sensing tools do not enable mapping on the soil-particle scale. GPR imaging of the subsoil to a depth of up to 30 m by transmitting electromagnetic radiation in the range 10-1000 MHz into the ground and receiving the scattered radiation is not sufficient to obtain the needed resolution, as the resolution of GPR up to 3 m depth is limited to 10 cm.

The millimeter-wave and Terahertz technologies proposed will enable filling in the missing data. They enable radiation penetration into the top soil layers, including the soil crust and root zone, at improved resolution compared to currently use ground-penetrating tools. Measurement of the moisture distribution along the soil profile, combined with a characterization of the soil crust, will enable a characterization of soil water infiltration and water impermeability. The spectral measurements with THz will provide more information regarding the ingredients and concentrations in the soil.  These tools will enable the characterization of structural processes in soils—at the surface and in the subsurface and subsoil in three dimensions and at the particle scale.

Millimeter-wave technology is currently undergoing rapid development and serves a variety of applications, e.g. material identification and characterization, medical research, communications, and identification of hidden objects through walls or clothes from a few tens of meters away. The preliminary results of an experiment carried out at the Soil Erosion Research Station indicate the feasibility of soil moisture measurement by the proposed active remote-sensing method. And thus suggest a novel application in addition to those mentioned above.