High Temperature Effects on Dielectric Constant of Moistened Soil Measured by Time Domain Reflectometry.

Using hot water (253~368K) for soil sterilization has been popular in Japan as an alternative to using methylbromide which appears to have  a strong negative effect on the environment.  One of the challenges of using hot water is deciding what amount of hot water is appropriate.To decide the optimum amount of hot water which should be applied, we need to know how hot water and heat behave during hot water infiltration. Time Domain Reflectometry (TDR) is widely used, but there is no precedent of using it under such high temperature conditions.
Thus, we examined temperature effects on High temperature dielectric constant of moistened soil, measured by TDR.
A sealed soil column 0.13m long and 0.05m inner diameter made of aluminum equipped with a two-wire TDR probe (0.08m long, 0.0018m spacing, with 0.0016m in diameter) and a thermo couple junction, was placed in a hot water bath. Sufficient time to attain thermal equilibrium throughout the column was provided, and the column was naturally cooled. The dielectric constant of moistened soil and electrical conductivity in the column were simultaneously measured using a computer-controlled-TDR system every minute. Temperature effects on the dielectric constant of moistened soil will be discussed.