EXPERIMENTAL DETERMINATION OF SOIL MOISTURE ON IRRIGATED LANDS FROM RADIOACTIVE SOIL EMISSION.

For several years the Valdai Hydrologic Scientific Research Laboratory has investigated the gamma method for determining the moisture content and moisture reserves of soils. This method is based on the measurement of the attenuation of the gamma radiation of the earth by the water in the upper soil layers. Methods have been developed for determining the depth of the active soil layer and the absolute average moisture content of this layer on the basis of the known relation between the intensity of the gamma field above the earth and soil moisture by weight. The paper describes the method and how it works, tests performed on it, and applications of the instrument.