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A low resonant frequency, dielectric based soil moisture sensor developed by Retrokool Inc. was tested in a Rincon loam, Yolo loam, and a Capay clay soil over a range of volumetric moisture contents. The response of this sensor was insensitive to changes in soil texture. However, the response of the sensor was influenced greatly by temperature changes and changes in salinity. A two factor factorial test was conducted to determine the effect of changes in dielectric constant and conductivity on the output voltage and frequency of this moisture sensor. The results indicated that as soil moisture content changed the output voltage, which is related to variations in conductance, changed much more than the output frequency, which is related to dielectric changes. When the terminals were coated with an insulating material, we were able to minimize the effect of changes in soil conductance and the sensor responded primarily to changes in soil moisture content.