Neutron Probe calibration

[Clint Shock]

Luke,

It will be interesting to see the range of answers.

My preference is to calibrate each soil and depth against the actual
volumetric water content in that soil at the time of access tube
installation.  Take bulk density and gravimetric samples as you install
the access tubes and make repeated neutron probe readings after the
probe has stabilized.  From there you are off to simple math and
regression analysis.  If a wide range of moisture conditions do not
exist at the time of installation at a given depth in a given soil, then
further sampling and measuring are warranted.  This very direct system
works and produces believable results.