Time domain reflectometry (TDR) has been popular to measure soil water content (WC) and electri-cal conductivity (EC) both in the field and the laboratory. Although a TDR probe detects average WC and/or EC along the probe length, a limited number of researches have been reported for the accuracy of averaging WC/EC in layered soils. We investigated the accuracy of averag-ing bulk EC in layered soils. A sandy soil and a loam were uniformly packed in three layers with various WC/EC in the constant temperature incubator. Each layer has a horizontally-installed three-rod TDR probe. Two vertical two-rod TDR probes were installed across the three layers of soil from the soil surface. We found that the vertically-probes average bulk EC of three layers with −9 to +17 % of accuracies. In addition, soil texture differences affected on different results of bulk EC between vertically- and horizontally-probes. However, we do not have to think dif-ferences of electrical conductivity between the vertically-and horizontally-probes because the differences in most of situation are less than ±10 %.
We evaluated hydraulic properties of a frozen soil based on the observed temperature, water content, and pressure head near the freezing front in a one-dimensional freezing column experiment for an unsaturated silty loam soil. Amount of unfrozen water near the freezing front was more than equilibrium amount of water according to the retention curve at the equivalent pressure head because freezing was a slow process. We proposed a modified-θ model to describe nonequilibrium amount of unfrozen wa-ter in the retention curve. Coupled heat and water flow equations were simulated with a modified-θ model as well as two other existing hydraulic property models: the clas-sical Harlan model, and the modified-K model. The Har-lan model overestimated water flow from the unfrozen re-gion to the frozen region. Although the modified-K model well simulated water flow in a frozen soil, calculated pres-sure heads and liquid water content showed unrealistic changes at the freezing front due to the extremely large decrease in the hydraulic conductivity. The modified-θ model agreed well with observed liquid water contents and pressure heads in a frozen soil. The unsaturated hy-draulic conductivity of a frozen soil based on the modified-θ model would be more physically feasible than other two hydraulic property models.