A method and apparatus for measuring the moisture content of bulk material which involves placing a length of leaky co-axial cable in the bulk material so as to be buried therein and spaced from an electro-magnetic sensor in the region of interest. A signal of high frequency electro-magnetic energy is injected into the cable, and at least one of phase and time of arrival of the signal at the sensor with respect to the injected signal is measured and therefrom the moisture content of the material determined. The electro-magnetic sensor is preferably a second leaky co-axial cable buried in the bulk material and spaced a selected distance from the first coaxial cable and parallel thereto. The spacing therebetween the coaxial cables is in the range of one to fifty feet and the frequency of the electro-magnetic energy is in the range of 20-500 MHz.