Abstract: A soil moisture sensor using sensor electrodes each designed with a larger capacitance for reduced sensitivity to soil resistance and increased sensitivity to soil moisture surrounding the electrode. The soil moisture sensor is provided as a pair of cylindrical rods each coated with a thin layer of dielectric material, which are buried in the soil or other medium and are connected to a conversion circuit in which the electrodes act as a variable capacitance. The capacitance developed by each of the sensor electrodes is related to the moisture contained in the soil particles surrounding the electrodes. An effective conducting area is developed by the soil particles in contact with the electrodes and this determines the value of the variable capacitance presented to the conversion circuit. The conversion circuit is a multivibrator in which the variable capacitance determines the output frequency, and this provides a measurement of soil moisture.