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Effect of moisture and bulk density sampling on neutron moisture gauge calibration

Allen, R.G. and Dickey, G.L. and Wright, J.L. (1993) Effect of moisture and bulk density sampling on neutron moisture gauge calibration. pp. 1145-1152. In: Proceedings of the 1993 NATIONAL CONFERENCE ON IRRIGATION AND DRAINAGE ENGINEERING. USA-UT-Park City, 1993/07/21-23.

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Three moisture and bulk density sampling methods were evaluated for use in
neutron gauge calibration. Each of the methods was comprised of a single
core or portions of a core taken during installation of a neutron access tube.
In addition to direct measurement of bulk density, the effect of using
"smoothed", "probable" and gamma-probe measured bulk density profiles was
evaluated. The use of these three alternative bulk density profiles in the
computation of volumetric moisture generally had insignificant effect on the
resulting neutron gauge calibration equation. The use of a depth-weighted
volumetric moisture profile generally improved calibration statistics, but reduced
slopes of neutron calibration equations (% moisture per count ratio). Overall,
a total core method which used a tractor-mounted, hydraulically operated
coring tool provided the most consistent calibrations with lowest standard errors
of estimate, although compression of soil along the perimeter of the cored hole
increased subsequent neutron count ratios. A "Madera" down-hole sampler
generally provided good calibrations, also. A third, small-volume, down-hole
sampler provided valid moisture and bulk density samples; however, the smaller
representative volume of the sampler relative to the sampling volume of neutron
gauges adversely affected slopes of some calibration equations.

Item Type: Conference or Workshop Item (Paper)
NWISRL Publication Number: 0810
Subjects: Research methodology
Mass Import - autoclassified (may be erroneous)
Depositing User: Dan Stieneke
Date Deposited: 20 Nov 2010 21:57
Last Modified: 01 Dec 2016 21:11
Item ID: 1061