In article ,
"Gordon Couger" wrote:

[Really BIG snip]

There is a very large market for a good soil moisture probe and it is a very
difficult problem because it is impossible to keep the soil in contact with
the probe and all the electrical method the inverse square law applies so
any small change close to the probe is greatly magnified. The Neutron probe
is the gold standard but getting the permits for it is a real bitch and
there is no easy way to test for radiation leaks.

:-)

About 40 years ago I spent a couple of brief periods running around
Queensland with a Neutron moisture probe in the boot of a black Holden
sedan "Z-car". (UQ used to hire cars from the C of A car fleet in
those days, and the number plates started with a "Z".)

We reckoned if we got picked up for speeding, we'd just show the cops
this ominous looking device with all its radiation warning symbols
in place, and we'd get a police escort to our next stop!

I highly reliable soil moisture probe that cost $50 would increase the
bottom line of most irrigated crops 5 to 15%.

Yeah. "Our" probe was a bit more expensive than that.
Also, even with this technology, there were serious problems caused by
water infiltrating the system. Tubes were installed in the ground and
the probe was inserted to take the readings as required. The main
problem was trying to stop water running down the tube/soil interface
at a very different rate to natural infiltration into the surrounding
soil.


Cheers, Phred.

--
LID