Change in SWC accurate with only a geneneric calibration?

[owner-sowacs@aqua.ccwr.ac.za]

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In order to promote healthy unbiased discussion, the following question is
posed anonymously:

The question : " Capacitance Probes : Claims have been made that a 'generic'
calibration equation will yield the same CHANGE in water content/ depth of a
summed profile as a site specific calibration curve but will have different
absolute values. This means that  a generic equation is just as helpful in
determining such measurements as plant water use as a site specific
equation.  Would be interested to hear anybody's views on this."

[My first inclination would be that the SWC change may be determinable with
a generic calibration, but the absolute amount of water is irrelevant when
vastly differing soil water potentials occur due to texture differences at
the same soil water content.
Bruce]