ABSTRACT
Nearly 50 yr after its first use, the neutron thermalization method remains the best available method for repeated measurement of soil profile volumetric water content (VWC)[1] because it is non-destructive, can be field calibrated with high precision, works successfully to depths not easily attained with other methods, and works well in stony soils and cracking clays in which other methods work poorly. Also, the large volume of measurement means that fewer replicates are required than for other methods to produce a given precision, that soil disturbance during tube installation has minimal effect on results (unlike electronic sensor methods), and that field calibration is successful because volumetric soil samples can be obtained from within the volume measured by the probe at each depth (unlike electronic methods used in access tubes that have much smaller measurement volumes). The technology is mature with a wide literature base describing applications and problems.
