Sensor description

The cosmic-ray neutron sensing technology is an innovative and non-invasive method for monitoring soil moisture. The sensing principle is based on the detection of neutrons that are generated when cosmic rays interact with atoms in the Earth's atmosphere. These neutrons, in turn, interact with hydrogen pools in the land surface, and thus, the intensity of neutrons detected near the ground surface is inversely related to the amunt of water in land biomass and the top layers of the soil. Typically, cosmic-ray neutron probes have a large sensing footprint, covering an area of approximately 12 hectares (about 30 acres) and can measure soil moisture up to a depth of 70 cm (about 28 inches), although typically most field applications span a depth between 5 and 40 cm. This makes the technology particularly useful for capturing spatially-averaged soil moisture over large areas, bridging the gap between point measurements and remote sensing. In hydrology, cosmic-ray neutron sensors are used for watershed studies, understanding water balance, and improving hydrological models. In agriculture, they are employed for irrigation management, crop yield prediction, and understanding the effects of soil moisture on plant growth. The technology's ability to provide continuous, real-time data without disturbing the soil makes it a valuable tool for both hydrological and agricultural research.

Figure 1. A) Stationary detector manufactured by Radiation Detection Technologies, Inc. (Manhattan, KS). B) Stationary detector manufactured by Hydroinnova, Inc. (Albuquerque, NM). C) Roving detector manufactured by Hydroinnova, Inc. (Albuquerque, NM).

Figure 2. Illustration showing the approximate sensing footprint of stationary detectors.