This research measures the effective thermal conductivity of a bed of granular potash particles and determines its relationship to moisture content by measuring the time dependent temperature of a heated steel spherical ball inserted into the bed. In these tests, the steel ball is heated to 5-10 degrees C above the bed temperature and then placed into the bed. As the heat diffuses throughout the bed, a data acquisition system records the temperature of the ball. The bed effective thermal conductivity is then calculated from these data. Tests were performed for five different ranges of particle sizes at five moisture contents (i.e., 0, 0.25, 0.5, 1.0, 2.0, and 3.0 wt %). The coefficient of determination for a linear fit between moisture content and effective thermal conductivity was found to vary from 0.913 to 0.998. This technique is expected to be practical for field measurements with granular materials, such as bulk fertilizers, because data can taken at selected points in the bed and because of its low cost, quick response, and simplicity of instrumentation.