Re: Aquaflex soil moisture sensor

[Adrian Orloff]

owner-sowacs@aqua.ccwr.ac.za wrote:

> NOTE:  To get off this list, send email to majordomo@aqua.ccwr.ac.za
> with the body of the message containing the line:
> unsubscribe sowacs
>
> I appreciated reading Adrian Orloff's latest response regarding the
> Aquaflex.  I have one additional question that I would like Adrian's opinion
> on.   Can the Aquaflex be installed vertically, either to a 3 m depth, or in
> a U or V shape to 1.5 m, so as to integrate water content in a complete root
> zone?  Aquaflex sensors can be installed into soil profiles in a range of
ways, as
> long as the bends in the sensor cable are not too sharp. V or U shaped
> (preferably) installations would be okay, however I believe that a better
> alternative would be to install the sensor into the soil profile on an
angle. This
> would allow for some vertical as well as horizontal averaging. We have some
> consultants that have installed sensors on an angle to measure from
approximately
> 20cm to 60cm. They feel this way will provide them with a useful vertical and
> horizontal average. As you would all know, the quality of data collected
with most
> soil moisture sensors is dependant upon the quality of the installations,
taking
> into account, site selection, (with regards to soil types, crop types and
> irrigation systems), and the actual installation of the sensors.

> This would be quite valuable in ET research and monitoring.  Or do
> layering or other changes in texture or water content with depth cause
problems?
> Varying soil profiles, with regards to soil texture and moisture do not
effect the
> accuracy or repeatability of Aquaflex. The average moisture content of the
soil
> through which the Aquaflex sensor passes will be measured.
>
> By the way, I was curious as to whether changes in horizontal distribution
> of water in the flooded pasture that Adrian described (or under drip
> irrigation) cause any change in the way that the Aquaflex will determine the
> average water content along it's 3 m length.  In other words, if water is
> nonuniformily added from irrigation to only part of the 3 m length, as this
> water is extracted, so that the spatial distribution of magnitude of water
> content changes over time, what impact does this have? If only part of the
> Aquaflex sensor is wetted, then the rise in soil water content will be
> proportional to the amount of water that reaches the sensor. If the Aquaflex
> sensor was installed in a park, and there was a strong wind blowing, which
caused
> ununiform water application, and only part of the sensor was wetted, then the
> increase in soil water content would be less than if the total length of the
> sensor had have been wetted on a still day, when the distribution
uniformity of
> the sprinklers was much greater.

Similarily, if the Aquflex sensor was installed in an area where the soil
changed
from sand to clay (over the horizontal plain), then the average moisture content
over the total length of the sensor would be recorded. The accuracy or
repeatability
of the measurement through the varying soil types would not be affected.

> Also, I was curious on the role that roots and tubers play on the aquiflex
> readings.  I presume that it would be similar to other sensors that read
> integrated water content, in that the water content of the tuber would
> impact any readings. All soil moisture sensors are effected to some degree by
> structures in the soil, whether they are tubers, roots or rocks. We have
> experienced general increases in soil water content at particular depths
in potato
> crops, using a range of sensors, where the water content of a tuber (as it
> developed), caused an increase in moisture content at a particular depth (if a
> sensor was in close proximity). In such cases, the increase in water content
> remained constant in proportion to the moisture content of the tuber, and the
> fluctuations, (wetting and drying) of soil moisture was the result of
irrigations,
> rains, drainage and plant water use. The increase in water content caused
by the
> tuber was a constant, therefore we would make slight adjustments to the
full point
> of the zone which we were monitoring. Aquaflex sensors would be effected
by such
> occurences, however beacuse of the large area of averaging, the total
effect may
> not be as significant as a greater volume of soil is measured. It will
also depend
> on the number of tubers within the sphere of measurement along the total
length of
> the Aquaflex sensor, as to the the total increase in water content.

Regards

Adrian Orloff

> Thanks for your thoughts and comments, Adrian.
>
> Rick Allen
> Utah State University