A capacitance-based moisture sensor may include a sleeve having an internal cavity, a container filled with soil or other material inserted into the internal cavity, and a pair of ring-shaped conductive bands around the exterior of the sleeve forming a capacitor and providing a frequency output. The rings positioned around a perimeter of the sleeve may be connected to a fixed inductor to form an oscillator with a variable frequency output. The sensor may be calibrated from the frequency output for each of a plurality of substances, measuring the volumetric water content for saturation of the material, and determining at least one fitting constant in an equation wherein volumetric water content is a function of the frequency output and a plurality of fitting constants.