How to Calibrate a Boom Sprayer: 1/128 of an acre method
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♪ [music] Hi, my name is James Locke. I’m a soils
and crops consultant at the Noble Foundation. What I’d like to visit with you about today
is how to calibrate a boom-type sprayer. Now there’s a lot of different methods on how
to calibrate a boom sprayer. We have a calculator on the Noble Foundation website that has one
method, but the one that I’m going to demonstrate for you today is the 1/128 of an acre method.
We’re going to measure the amount of output for each nozzle — what it would cover as
1/128 of an acre. We can then measure that output in ounces. 128 ounces are in a gallon.
So, 1/128 of an acre — ounces equals gallons per acre, which is what we have to have in
order to know how much chemical to put in the tank. We need to know how many gallons
per acre we’re going to apply. Without that information, it’s impossible to calculate
the correct amount to go into a spray tank. OK, the supplies that we’re going to need
in order to do this: we need a measuring tape — something to measure our travel distance,
something to catch output from the nozzles — something that measures in ounces. Ounces
equals gallons per acre. Stopwatch, a measuring tape — or perhaps a shorter measuring tape
in order to measure the distance between the nozzles. Something to record our information
on. A calculator and flags or some way to mark the beginning and the ends of our travel
distance. OK, the first step that we want to take before
we get ready to actually calibrate the sprayer is inspect the sprayer to make sure that it’s in
good condition. You want to make sure that all of the hoses are in good condition — no
abrasions or cuts. You want to look at each one of the nozzles, make sure that they’re
undamaged. And on a boom sprayer, you want to make sure that they all match. If you mix
nozzles on a boom, it’s impossible to get a good calibration on it. You always want
to use clean water during the calibration to limit your exposure to chemical. The pump,
the in-line filters, tractor that you’re operating on – you want to make sure that everything
is in good working condition before you get started. The next step that we need to do is measure
the distance between nozzles. In this case, it’s 20 inches from the center of the nozzle
to the center of this nozzle. All of these nozzles are on a
20-inch spacing. We look at our Noble Foundation spray chart for a nozzle spacing of 20 inches.
We now need to measure out a 204-foot travel distance. What we’re going to do now is measure out
our 204-foot run length. This corresponds off what we got from the chart for a 20-inch
nozzle spacing in order to get our 1/128 of an acre per nozzle. [Natural sounds: measuring tape, tractor] What we just did is we ran the distance that
we had from our chart that would allow us to achieve 1/128 acre for each one of those
nozzles. Now we can go back and check the output from each nozzle for this amount of
time — in this case, 37 seconds — and that will give us, in ounces, our gallons per acre. OK, now we need to set the pressure to match
the nozzles that we’ve got on the boom. The nozzles on this particular boom are a
a ???. Thirty pounds of pressure is right in the middle of the range that we want to
use, so we’ve got the pressure gauge set to 30 pounds of pressure to match what these
nozzles need. So, now I’m going to come back and I’ll catch
each nozzle for 37 seconds to match our 1/128 acre. [Sounds of tractor, water pouring into cup] So, what we measure here, is in that time
period we caught 20 ounces. And we repeat this for every nozzle along the boom to make
sure that they’re all within an acceptable range — usually within 10 percent of this
20-ounce target. In order to determine what our final calibrated
gallons-per-acre is, what I’ve done is I’ve added all of these numbers together. Each
one is the ounces for 37 seconds that we collected from each nozzle. There’s 18 nozzles, divide
that total by 18, we ended up with an average of 19.83 ounces in that 37 seconds. I’ve rounded
that to 20 ounces. And this 20 ounces indicates that we’re putting out 20 gallons per acre,
which is a very good, acceptable level for the type of application we generally want
to do. If you need to make major adjustments to that gallons per acre, we can either speed
up or slow down – slower, you’re putting out more; faster, you’re putting out less
— or we can change nozzle size to make major changes. Or if we just need to tweak it a
little bit, then we can make some adjustments in pressure. I’m then going to record which tractor this
was done on, the gear, rpm, and if I have multiple sprayers — what the sprayer identification
is. That way I’ll have this information — I’ll have it stored — and I won’t have
to remember it for future uses until I calibrate again. OK, just as a summary for why we go about
doing the whole calibration procedure: you know, first and foremost, it’s necessary to
know how much chemical we’re going to put in the tank in order to achieve our desired
rate. If we don’t know how many gallons per acre we’re putting out, we run the risk of
either not putting enough chemical in and not putting enough chemical out on the pasture,
we don’t get the type of weed control or insect control — whatever it is that what we’re
trying to manage — we have poor efficacy. Or perhaps we put too much out and then we
end up with illegal pesticide residues that could potentially make animals or people sick,
be harsh on the environment. So in order to be good stewards of the ag chemical products
that we use, we’ve got to be able to do this calibration. And, if for no other reason,
it does save money knowing how much you’re putting out in order to get the most bang
for your buck.

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