Re: Diviner 2000 access tubes

[Mandy Adams]

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I  have been using the Diviner for a number of months now and have found it
to be useful when using relative data rather than direct values. The reason
for the clay slurry is to get the contact between soil and tube. By using
the same clay every time it is easier to compare across soils. Sentek now
has a sand augering kit which consists of a tripod and a smaller auger. It
allows you to auger the hole inside the tube and insert it as you go so the
issue of a sand cavity is not there.

Mandy Adams
BSES Proserpine

[Bruce comments: I think the stony sand issue was a different problem where
the stones prevent a neat straight hole from being augered and/or leave
cavities wher the stones have been dislodged, or adjacent to an access tube
that has been deviated from straight.
But I have experienced the problem with dry sand falling down the hole
before the access tube can be pushed in - your only choice is then that
method you mention!
Bruce]

----- Original Message -----
From: <owner-sowacs@aqua.ccwr.ac.za>
Sent: Wednesday, May 31, 2000 5:30 AM
Subject: Re: Diviner 2000 access tubes


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Jac,

I would be very leary of this setup. Depending on the frequency of wetting
events (rain or irrigation) the clay annulus could be very much out of
phase with the sand for important lengths of time. It surprises me that the
tubes would be installed in this manner. Installing the Diviner 2000 access
tubes directly in sand should be very easy as long as one does not auger
too far ahead of the tube (can cause a cavity to form if sand collapses
into the auger hole).

Steve

At 12:53 AM 5/27/2000 +0000, you wrote:

>I recently acquired a Diviner2000 moisture probe. The supplier installs the
>access tubes by drilling a hole of 10mm  bigger OD, inserts the PVC tube
and
>settles it in with a clay mixture (similar to potters clay - the exact
>compostion I am not sure of), to ensure perfect contact between tube and
>soil.
>
>We work with sand (as in sand dunes) with moisture holding capacity as low
>as 45 mm/m.
>
>I am wondering what the effect of the clay band in direct contact with the
>tube could be.
>Can I assume that the sand-clay will reach equilibrium, in a short enough
>time to give me the correct response.
>
>Your comments will be appreciated.
>
>Thank you: Jac le Roux
>jac@besproeiing.co.za
>
>
>
>
>

___________________
Steve Evett, Soil Scientist
USDA-ARS, 2300 Experiment Staton Rd., Bushland, TX 79012 USA
806-356-5775, FAX: 806-356-5750
srevett@ag.gov, http://www.cprl.ars.usda.gov/programs/