Author - Bamert Seed

Calibrating A Boomless Sprayer


Hello. My name is James Locke, I’m a soils and crops consultant with the Noble Foundation. What I’d like to visit with you about today is how to calibrate a boomless or Boom Buster-type sprayer. These type sprayers are very common in range and pastureland because they don’t have wide booms that stick out and you’re able to maneuver around trees and brush and


There are a lot of different ways to calibrate a sprayer like this. We have a method on our website — a calculator where you can plug in your output data and then it will calibrate it for you.


The method that we’re going to be demonstrating today is called the 1/8 of an acre method, where we calculate how much spray we’re putting out over what would be the equivalent of an eighth of an acre. We measure that in pints. The number of pints ends up equaling our gallons per acre. We have to know our gallons per acre because that’s the only way that you can know how much material to put in a tank to achieve the desired output rate.


The supplies that we’ll need in order to calibrate a boomless or Brush Buster sprayer, we need a measuring tape — at least 200 to 300 feet. Two catch buckets in order to catch the output from the nozzles. Something that will measure in pints in order to measure the output from the spray nozzles. Calculator, stopwatch, something to record the information on and then flags to be able to mark the ends of our timing runs and the width of our spray Pattern.


One of the first things that you do whenever you’re getting ready to calibrate the sprayer is make sure everything’s in good working order. Look at the nozzles, make sure that they’re clean and undamaged. Inspect the hoses, make sure that they’re all undamaged, no bubbles or cracks. Make sure that your filters are in place and no damage there. Inspect the pressure regulator, make sure there’s no cracks or leaks — everything’s operational there. Check the pump to make sure that it’s in good condition — no cracks, leaks, anything like that. Make sure it’s correctly hooked up either to the PTO or the hydraulics depending on what type of a tractor pump system that you’re using. Also inspect the tractor: check oil and make sure that the tractor’s in good operating condition for the operation you’re about to undertake.


What we’re going to do next is we’re going to set the pressure. With this particular type of nozzle that were using, we’re targeting about 30 pounds of pressure. So if we can go ahead and get her started … Now we’re getting the pump started. Our pressure is set about where we want it to be and at this point we turn the sprayer on.


This part of the operation — what we’re doing is we’re testing how wide a spray width that we’ve got. The way that we do that is we’ll come over here, measure as far as the wetted area, which is about right here. Then I’ll come to the other side of the spray pattern. And we’re measuring how wide the entire pattern is. Now we’ll turn the sprayer off. Take our tape measure and measure what the total spray width is. So the total width is 34 feet.


So what we’ve done is we’ve measured the entire spray width of what the sprayer will cover and we now need to calculate the effective spray width, which is 80 to 85 percent of what the total coverage is. So, our total spray width is 34 feet. The effective spray width, we’ll call it 34 times .85 — that gets us to 29 feet for 85 percent, or 27 feet for 80 percent. So just call it, basically, a 28-foot effective spray width.


We had our total spray width was 34 feet. Between 80 and 85 percent would be about 28 feet for our effective spray width. So then we look at this chart on a sticker that’s available from the Noble Foundation and roughly at 27 and a half feet, which is pretty close to what we’ve got, we need a distance of 199 feet. The reason we use that is 199 feet times our effective spray width is going to give us our 1/8 of an acre, which is our target for what we’re trying to emulate with this calibration procedure. Our next step is to measure out this 199 feet and determine how long it takes us to travel that distance.


So what we’ll do is we’ll put a flag in the ground, measure 199 feet, put a flag in the ground on the other end and then I’ll use a stopwatch to record how much time it takes us to travel, just like if we were doing the actual application in the field. Now I’m going to measure out the distance.


So what we just did is we measured the time that it took him to travel this 199 feet. What this does — with our distance and that time — that tells us how long it takes us to cover 1/8 of an acre, in this case, 36.4 seconds. Now we’ll go back and we’ll actually catch the output from the nozzles for this amount of time.


And here we go … So at this point what we’re going to do is measure the output from the right hand side, we’re going to measure it in pints. From that side, we’ve measured 102 ounces. There’s 16 ounces per pint. We have a 102 ounces divided by 16 ounces in a pint, equals 6.375 pints in our 36.4 seconds.


Now we’ve measured from the other side. We got 98, 100, 102 … we got 104 ounces from the other side. So 104 ounces divided by 16 ounces per pint is 6.5 pints. So we have 6.5 pints from the right side plus 6.375 pints from the left side is 12.875 pints total. I don’t believe that we’re really that accurate, so I’m going to round this to 13 gallons per Acre.


OK, what I’m going to do now is: I’ve calculated what my total output is, I’m just rounding it to 13 gallons per acre. Now I’m going to record which tractor I’m using this on, what my gear is, what my rpm is so that I don’t have to keep doing that. And if I’ve got multiple sprayers, then I’m also going to record which sprayer this calibration is for. I’ll keep this on record so that I can refer to it in the future.


A few additional points to mention: we were calibrating with water in this case — you always want to use clean water during the calibration to limit your exposure to chemical. We also want to point out that if the calibration gallons per acre that we arrived at using this procedure is not correct — it’s not reasonable for our application — make minor adjustments by changing the pressure or you can make more significant adjustments either by changing the nozzle size or the speed of travel. That’s where you make major adjustments.