Absolute Minimum Soil Disturbance Method
TomRinAZ-USA
efforts by the Univ. of Arizona on a long-term project monitoring
several ornamental tree species' annual water use under different
irrigation frequencies and gross volumes. TRD is currently installed
without any continuous monitoring or logging capabilities, which is
why I am involved. To bring highly reliable, low-cost soil moisture
data in discrete profiles into a cost-effective data logger network.
The challenge posed to me was to install the new system (Data Recorder
by Acclima/Jain, Meridian, ID, USA) with no detectable impacts to the
established research blocks.
I have decided to install the sensors on an incline jig such that
every sensor at each depth is installed essentially the same, without
any impact to the soil surface above. Bubblers are installed, and the
insertion tunnel must not provide a courseway for irrigation to
follow.
Does anyone have a better way to bore the 2" hole on an incline, other
than a simple bucket auger? Would you agree that the sensor should be
inserted in a slit only a little larger than the probes, and then
sealed tight with a uniformly prepared, screened to <0.125" (3.2 mm)
slurry? Making the slit is the real challenge, and I have a water and
vacuum tool built to achieve that.
Rupert Knowles
I think you are trying to reinvent the wheel! Sentek (www.sentek.com.au)
spent a lot of effort into designing probes and methods of installing them.
Unless the soil is full of stones, they work well. I remember standing on
elevated planks of wood installing probes in research plots where it was
vital not to disturb the surface soil. I have not been involved with Sentek
for 5 years, but I think the probes and the installation kit have probably
been refined even further.
Expensive? May be - but you get what you pay for!
Rupert
Rupert Knowles
Horticulture and Forestry Consultant
+93 (0)799 652 659
+44 (0)7704 444 218
r.kn...@aspects.net
c/o GPFA, Wazir Akbar Khan, Street 13/2 left, House 128, Kabul
Jim Bilskie
I have quite a bit of experience with field installations so maybe can offer
some suggestions. Here are a couple of questions that will help me
understand the installation and limitations and I am happy to offer from my
experience.
Which sensors are you installing?
At what depth do you want to monitor water content?
What is the soil that the trees are planted in?
What about a sensor that has 30 cm rods that can be easily inserted in the
soil surface thus zero soil disturbance? Is monitoring the top 30 cm
enough?
My regards,
Jim
Josh Hanks
http://www.inmtn.com/index.php/cproducts/soil_monitoring/diviner_2000/diviner_2000_video
Best Regards,
Josh Hanks
Intermountain Environmental, Inc.
435-755-0774
Logan, Utah
Tom,
I think you are trying to reinvent the wheel! Sentek (www.sentek.com.au)
spent a lot of effort into designing probes and methods of installing them.
Unless the soil is full of stones, they work well. I remember standing on
elevated planks of wood installing probes in research plots where it was
vital not to disturb the surface soil. I have not been involved with Sentek
for 5 years, but I think the probes and the installation kit have probably
been refined even further.
Expensive? May be - but you get what you pay for!
Rupert
Rupert Knowles
Horticulture and Forestry Consultant
+93 (0)799 652 659
+44 (0)7704 444 218
r.kn...@aspects.net
c/o GPFA, Wazir Akbar Khan, Street 13/2 left, House 128, Kabul
-----Original Message-----
From: sow...@googlegroups.com [mailto:sow...@googlegroups.com] On Behalf Of
TomRinAZ-USA
Sent: 06 January 2010 22:21
To: sowacs: soil water moisture content measurement systems and sensors
Cc: sc...@acclima.com
Subject: Absolute Minimum Soil Disturbance Method
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Andrew Leakey
Over the last 5 or so years we've developed a series of power-auger methods for installing sentek tubes for our research into crop responses to global climate change. The latest incarnation is a modified giddings probe mounted on a small tractor (see attached picture). Two people between them install 100-200 tubes in 2-3 days at the beginning of each growing season without significant disturbance and we're really happy with the data quality. It is a lot easier in a row crop that is planted each year and we have a largely rock-free soil, but something similar might work for you depending on the spacing of your trees.
cheers
Andrew
**********************************************
Dr Andrew Leakey
Assistant Professor
Department of Plant Biology
Institute for Genomic Biology
1402 Institute for Genomic Biology
University of Illinois
1206 W Gregory Dr
Urbana
IL 61801
USA
lea...@uiuc.edu
Office +1 217 244 0302
Cell +1 217 766 9155
Fax +1 217 244 2057
http://www.life.uiuc.edu/leakey
jean piaget
Moisture monitoring without an idea what the root configuration of the
plants can easily leads to wrong conclusions being made. Do you have a
picture of root depth and lateral growth which determine where and how deep
to insert the probe or probes?
I so seldom see root characteristics mentioned in soil moisture reports yet
know from experience how important a role it plays in field experimentation
as there is no correlation between texbook description and actual facts in
nature.
Naturally the demand for no soil disturbance on the one hand and root
studies on the other hand makes me sympathise with you.
Jean
Tom
I appreciate your post. I will be bound to favor the Acclima sensor for
it's reliability and price-point, and the software....at least for now. I am
an independent consultant as you know, and I represent no manufacturer. I do
want to use the product that will make both my client, and me in their eyes,
shine. I mention your paper "Statistics for Sensor Density Decisions" all
the time.
The researchers will decide what depths. Budgets may limit the depths to
3.....like 6", 18" and 50". There are treatments and replications.
I think my tool for installing the sensors would work well with your
sensors.....inserting the probes in a slit down deep.
The soil is a loam, as I recall, with a distinct caliche layer across most
of the 20 or so acres, according to the other researcher.
I am coming in after the experiment design, but I believe they wish to
develop water balance's for the different species, and probably crop
coefficients.
The New Mexico State has developed some such for a few trees, including
Mesquite, which is very interesting.
Tom A. Reynolds, CID
Water Balance, LLC
Tempe, AZ
(602) 463-5072
www.waterbalance.net
TomRinAZ-USA
I think the only monitoring techniques that can be excused to let the
surface be influenced by a 2" protrusion is the neutron probe since it
reads a sphere about the size of a volleyball (or basketball,
depending on the VMC). I was always struck by the designer's disregard
for the obvious impacts directly above the realm of detection with the
Sentek system. Another version (AquaSpy) seem to have the same
problem, especially in turf. How can you have a big void at the center
of the reading realm (zero water use column), which does not use water
without changing the VMC inches away from the void? What would happen
if instead the detection was immediately in contact with a 2" column
ofhigh-retention sponge material. See where I'm going with this? For
the researchers that pressed me on this, and I concurred, we prefer
zero surface affects.
So, thanks for the input, but I think I'll continue improving "the
wheel."
On Jan 6, 7:51 pm, "Rupert Knowles" <r.know...@aspects.net> wrote:
> Tom,
> I think you are trying to reinvent the wheel! Sentek (www.sentek.com.au)
> spent a lot of effort into designing probes and methods of installing them.
> Unless the soil is full of stones, they work well. I remember standing on
> elevated planks of wood installing probes in research plots where it was
> vital not to disturb the surface soil. I have not been involved with Sentek
> for 5 years, but I think the probes and the installation kit have probably
> been refined even further.
> Expensive? May be - but you get what you pay for!
> Rupert
>
> Rupert Knowles
> Horticulture and Forestry Consultant
> +93 (0)799 652 659
> +44 (0)7704 444 218
> that.- Hide quoted text -
>
> - Show quoted text -
Tom
Jean,
Empirical evidence of many, many trees irrigated with drip system, bubbles, and sprinklers, either dug up, water-vacuumed, or blow over explains most of what you allude to. Dr. Jimmy Tipton (UofA) did a 3 year study on the root development under different emitter layouts and irrigation treatments. I am certain the researchers are aware if it. I recall observing the many different soil moisture depletion accounting (using a N.P.) in cotton, in the same fields, year after year.....notably cotton and wheat. I recall the lead research (Dr. Schuck) saying she agreed with me that 18" depth was the most reliable "high use" part of the profile. We also believe that one sensor below what we believe to be the management extents, like at 48", would stand as the depth we could begin to define as deep percolation. I believe we must deploy adequate numbers of sensors for a landscape, and then determine and describe site's unique characteristic…for those that will assume the reins behind us. Modeling and design assumptions only get you in the ball park. I'm all for routine monitoring when reasonable (sagacious).
The researchers work may be aimed at trying to establish a water balance model for the different species, tantamount to lysimeter investigations. This will be useful for design, but not what I would use to manage plant establishment or years 0.5 to 10. I happen to believe, after Year 10, nobody knows where (a boundary on a map) an individual tree acquires all of its water....actually year 6 - 9 is pretty dubious also.
As you probably know, as advocated by others, once an orchard (or even a large residential landscape with many species) achieves 60% cover, we move away from individual plant water management to management unit management. One of the odd things about our xeriscapes in Phoenix, Tucson, Coachella, and Las Vegas, we may never obtain landscape canopy coverage greater than 40% or 50%. Makes me want to go out there with a trencher and cut-off all those wander's to a nice radius around each plant.
Another thing is what we believe about drip irrigation's wetted onions. As an ag-extensionist and I discussed a long time ago, we monitor soil moisture in a particular way around representative emitters. The soil moisture depletion intensity within, and at the fringe of the wetted onion should develop a behavioral response to more or less frequency and volume, relative to climate. One can observe an expanding wetted onion over time, which could be interpreted to mean irrigation applications above plant demands. And contracting wetted onions (mostly in the X-Y planes) a sign of deficit irrigation. It's a nice concept anyway. Cheers !!
Ben
You should consider the general problems of electromagnetic methods
and access tubes. Here is a very nice article about the limitations:
Evett et al., 2009: Soil Profile Water Content Determination:
Spatiotemporal Variability of Electromagnetic and Neutron Probe
Sensors in Access Tubes, Vadose Zone J 8:926-941
http://vzj.scijournals.org/cgi/content/abstract/8/4/926?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=&author1=evett&andorexacttitle=and&andorexacttitleabs=and&andorexactfulltext=and&searchid=1&FIRSTINDEX=0&sortspec=relevance&resourcetype=HWCIT
Regards
Benjamin
Jim Bilskie CSI
Thank you for the informative and kind reply. I'm happy to offer suggestions and my experience whether you are using Campbell Scientific sensors or not. It's a big challenge to install soil water sensors in an existing study area with minimum disturbance.
I can suggest that it be remembered that soil structure will rejuvenate after some number of hydration/dehydration or freeze/thaw cycles. So maybe make this a reminder point to the investigators. It's important to locate the sensors in the best place to monitor water content and accept that there will be some disturbance. This tree study is apparently a long term one and the disturbance effects will effectively be amortized over time. The geometry of some sensor is better than others for recovery from disturbance. Recovery from installation of simple straight rods will be the quickest.
My regards,
Jim
Jim Bilskie, Ph.D.
Soil Physicist
Campbell Scientific, Inc.
Tom
Tom A. Reynolds, CID
Water Balance, LLC
Tempe, AZ
(602) 463-5072
www.waterbalance.net
-----Original Message-----
From: sow...@googlegroups.com [mailto:sow...@googlegroups.com] On Behalf Of
Jim Bilskie CSI
Sent: Saturday, January 09, 2010 11:22 AM
To: sow...@googlegroups.com
terence mcburney
rather than volumetric moisture content. Soil bulk density changes that
occur due to soil compression at the probe soil/ interface during
installation may alter the water apparent content reading but water
potentials will tend to equilibrate with the surrounding undisturbed soil,
since water moves along gradients in water potential. A range of suitable
probes are avialable, including those developed by my company
www.mcburneyscientific.com.
Terry McBurney
Hi, Tom:
My regards,
Jim
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