Telemetry Schedules Irrigation
With The Latest Technology Farmers Keep Keener Eye On Crop Moisture
PORTAGEVILLE, MO.
Using telemetry to schedule irrigation can
provide a big boost to yields, according to
Dr. Joe Henggeler, irrigation specialist
with the University of Missouri at the Delta
Center in Portageville.
“Irrigators who schedule are making about 13
bushels more corn,” he said. Most of these use
the Woodroof method or the Arkansas Scheduler.
At $4 corn that’s $50 an acre, on soybeans
with about an 8 bushel increase at $10, that’s
$80 an acre. Cotton is the same way, so scheduling
is probably one of the biggest, best ways
to make an improvement for an irrigator.
“One special type of scheduling actually uses
soil moisture sensors,” Henggeler added. “Instead
of having a computer predict water needs,
you actually look at what the sensors are showing
you, schedule irrigation according to that;
and, from our survey, the indications are that
you will see an even greater yield bump.”
Henggeler said the sample size of farmers
using sensors was very small, so he doesn’t
want to mention the amount of yield increase,
but it was much higher than the 13 bushels
extra from just using computer scheduling.
However, he’s sold on the concept.
“All methods of scheduling are good, but this
looks really good,” he said. Some problems with
normal methods in use is you have to go out
and collect the data, then graph it which can be
a problem especially in the middle of the season.
Farmers have time earlier on to play with
it and get it set, but after that point they’ve got
to leave it to take care of itself.
“So what is a possibility now is using telemetry
to schedule our irrigation,” Henggeler said.
“With sensors out in the field, instead of going
out to collect the data, the data is sent to the
farmer. Now you can use tensiometers or you
can use a gypsum block type of equipment.
There is a special probe with the capacitance
method which will give you graphs of the water
content in the soil. We recommend placing
them at three depths, 6, 12, and 18 inches so
you’ll get a graph for each one.”
The value of the 18-inch probe will stay fairly
flat if you’re irrigating correctly. If you’re not
putting enough water on, it starts to drop down;
if you’re over irrigating it starts to go up. It’s a
good indicator. The top one, the 6-inch,
bounces up and down with the rains and the
water use, gauging the current activity.
“What we actually like to do is average all
three values at one site,” he explained. He presented
some charts showing some actual measurements.
“Here is the average of the three
different depths and it is presented as a curve.
There are three things this curve can tell you
and this is the most important one. After an irrigation
you see the extraction rate over time is
pretty linear. That is, each day you use the
same amount of water as you did the day before;
but at a certain point as you run that
water it’ll start to flatten out. That is when you
know it’s time to irrigate.”
The sensor will incorporate everything, the
soil condition, if there are hard pans, if there’s
disease problems, bugs. All will be incorporated
because the sensor measures actual conditions.
“These sensors will also tell you if there’s a
problem of waterlogging after you irrigate,” he
noted, pointing to another curve. “Normally we
get a nice rate of water use, but for the first
three days after watering, or after a 1 1/2 inch
rain, it was fairly flat meaning that it was not
using much water. We actually get hurt as
much during this period as we do during
drought. We never could tell that before because
when we collect the data by hand it is like
two or three days before it’s available anyway
because you couldn’t walk out into the field; so
you never really saw what happened initially.
But collecting it telemetrically you see it.”
The sensors may also show big spikes after
rains and that tells you that this water comes
and rapidly evaporates. You begin to realize,
whether it’s rain or irrigation, there’s always a
certain amount of water that’s lost to the atmosphere.
“You’ll learn not to water too often because if
this atmospheric loss is about one-tenth of an
inch and you are applying 0.4 inches, you’ll lose
about a quarter of it sacrificially,” Henggeler
pointed out. “That’s what the sensors will show
you.”
Recommendations on a pivot include using
three locations. The reason for that is a typical
pivot has distribution issues. If only one is in a
location it might be placed in a wet or dry spot.
With three there should be an average.
The placement at the three depths should be
at three locations. They also should be on the
outside part of the pivot because that actually
covers more ground than the inside. Avoid the
area wetted by the end gun because that’s kind
of uneven.
“Once the system is installed, there are basically
two options to get that information telemetrically
to the computer,” he explained. “In
one situation, the sensors’ data is sent directly
to your computer; and in the other it’s sent to a
medium level receiver, which acts as a data station
which then sends it to the Internet. Sometimes
you need repeaters because it will only
transmit so many feet. The nice thing about the
Internet option is that you can check up on it
even if you are on the other side of the world, or
you can have a crop consultant look at it. Both
the home PC and the Internet options can be
set up to make calls to your cell phone if certain
trigger levels are ever reached.”
Presently Henggeler is searching out systems
that really work, studying the various methods
of getting the information to the farmer.
“We’re doing a test with three different systems
and we’re looking at how the whole communication
system works and we are noting
agronomically how it’s telling us when to irrigate,”
he said. “ With some systems, if your
computer goes down you don’t get any data because
there’s no extra data storage in any of
these transmitters or repeaters; so if you’re
computer is out for a couple of days you’ve lost
that data. Other types of transmission devices
are better. Generally there are two frequencies
that the government allows people to use; one is
at 900 megahertz and the other is at 2.4 gigahertz.
The 900 megahertz has a much longer,
about two or three times the range as the other,
so those are probably the better ones to use.”
The cost of the systems are going to vary. It
will be a little bit cheaper if the information is
sent directly to the PC than to have it on the
web.
“You can have systems that would be $6 or $7
an acre and this would actually go lower, for example
if there were more acres,” he explained.
“This was used on 100-acre estimates, but a
typical pivot is 135 acres and this goes lower. If
you have two pivots right next to each other,
then the cost is almost half of that. So basically
for $4-$5 in a lot of situations you can schedule
by telemetry.
“If you go back and look at the yield increase
that soil moisture sensors have versus present
scheduling methods you see a really fantastic
return on investment,” Henggeler noted. “That’s
why I am so excited about this as just common
sense. You have the science, but you also have
the human side where you need to find out the
pitfalls that will show up, and things like connectivity,
connectability and all that; we’ve got
to get rid of all those.
“If you go with the Internet option to store
your data there are some real pluses,”
Henggeler said. “If you have an ipod you can
look at it, if you have a consultant he can look
at it. We’ve heard stories where a consultant
will call and say ‘what is going on with pivot
number 4, is something wrong?’ The farmer will
take a look and be able to correct the problem.
So you have more than one set of eyes keeping
track of it.
“What we are interested in is linking telemetry
and irrigation at the University of Missouri, and
we’re going to explore this, using the University
of Missouri ag website,” he continued. “So the
data can be combined with information from
weather stations. A farmer can then check his
soil moisture, the temperature, real time wind,
and all this other information. He can pull future
forecasts of rain, or various other things to
help determine the need for irrigation. The university
would send that information in e-mail
form to farmers.
“That’s what we’re shooting for, and we’re
going to be talking this winter with the IT people
to see basically the best way to do that,” he
said.
“There are a couple of large farms in this area
using the telemetry system. They are top producers,
one focuses on cotton and the other on
corn/soybeans. Both report excellent results
and increased profits; and both also agree that,
as large as they are, it is best to turn the job of
monitoring and interpreting the soil moisture
data over to just one person who then calls the
shots of when to irrigate.”
The graphs generally speak for themselves,
but the moisture level lines can be confusing.
Henggeler says it’s like a sonogram; everyone
can see that there’s a baby there, but only the
specialist can tell you if it’s a boy or girl. This
same equipment has been used by several seed
companies to learn more about soil water uptake
of their varieties.
“Basically, in conclusion, this telemetric irrigation
scheduling is very reasonable and, easily,
for $7 to $10 an acre – or about double that
for the Cadillac system – you can do it,” he
summed. “It would be a lot less if there are pivots
nearby and, with the expected yield increase,
especially if you’re not scheduling
already, it would almost undoubtedly pay for itself
in terms of months rather than years.”
The cost to send the information to your PC
will be less, but there’s more headaches in connecting
it; however, you can instantaniously see
the information, but only if you’re at your computer’s
location. If you go to the website the
data won’t be instantaneous because most sites
will only collect the data about twice a day; so
you’d see data that is 12 hours old, but you
would have a second set of eyes looking at it.
However, no matter where you are in the world
you can check the soil moisture of your crop.
“This looks good. I really think we’ll see a lot
more of this in Missouri. Missouri will be the
first state to develop a statewide concept. We’re
focusing specifically on pivots because they can
also respond with the small water amounts and
we’re developing a holistic plan for doing this.
We are talking with the companies that make
this, and they like to see a lot of applications for
their systems but they don’t have the specific
information of how to make one specific system
work. So they’re very excited in what we’re
doing here and I think when it’s all said and
done we’re going to present, basically, a turnkey
package; so for about $3,000-$4,000 total a
person will be able to put in a 135-acre pivot
and have it telemetrically tell them exactly what
the moisture situation is.” Δ
BETTY VALLE GEGG-NAEGER: Senior Staff
Writer, MidAmerica Farmer