Use of Neutron Meters in Soil Moisture Measurement: Progress Report of Task Force on Use of Neutron Meters, Committee on Hydrometeorology

Devices using neutron energy absorption or gamma-ray scattering techniques for soil moisture and density measurement have reached a stage of development permitting many practical applications. A survey on neutron meter use in hydrologic studies, construction, and agriculture indicates that portable nuclear equipment permits simple, rapid, nondestructive density and moisture measurement. The on-the-spot results and opportunity for repetitive observations represent the principal advantages. Results from depth observations are more satisfactory than those from surface observations. Depth-moisture equipment is used most extensively in hydrologic and agricultural studies. Surface moisture and density equipment are used widely in construction activities, particularly in soil compaction testing. Equipment now available (1964) is generally dependable and should provide reliable results. Radiation hazards are small. Questions of interpretation and equivalence of results have delayed acceptance of the nuclear methods in lieu of standard tests in construction; however, use in spot checking and selection of sites for standard testing is growing. The survey report reviews principles, equipment, applications and procedure, summarizes advantages, disadvantages and problems, and includes a selected bibliography.