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Your No. 1 goal should be to increase the efficacy and control the pest.Your second goal is drift management, and those two goals go hand-in-hand.But if you let drift management become the No. 1 goal, you’re not always going to kill weeds, so we have to keep No. 1 in mind here

Paul L. Hollis

April 22, 2013

9 Min Read
<p> BOB WOLF, PROFESSOR Emeritus at Kansas State University and president of Wolf Consulting &amp; Research, describes new sprayer technology at the Sprayer Clinic held at the E.V. Smith Research Center in Shorter, Ala.</p>

New herbicide formulations hitting the market in the near future are sure to include more specific application requirements, making it even more important that farmers and commercial applicators improve their practices.

“Regulators and company representatives are writing labels for these new products, and they will be more specific to application,” says Bob Wolf, Professor Emeritus at Kansas State University and president of Wolf Consulting & Research.

“You will be required to follow and do whatever it says on that label. We need to look at those application practices and understand how you can improve them.”

Wolf spoke at the Sprayer Clinic held at the E.V. Smith Research Center in Shorter, Ala., this past January.

Farmers typically think that being an applicator includes driving a sprayer and doing the spray jobs, says Wolf.

“I define an applicator as anyone who has a say about the decision-making process in that spray application. There are people who are not actually running the spray rig, but have a lot to say about how it is set up and how it operates,” he says.

This is especially common on the commercial side of the business, he adds.

“The guy running the sprayer rig oftentimes does not have the opportunity to set the parameters for that operation. It’s important that training be directed to everyone.

“There will be some major changes in the application processes, specifically as it relates to the label, and the label is the law,” says Wolf.

If you’re going out into the field with a tank-load of a herbicide mixture to spray, your No. 1 goal as an applicator is to kill the weeds, he says.

“Your No. 1 goal should be to increase the efficacy and control the pest. Your second goal is drift management, and those two goals go hand-in-hand. But if we let drift management become our No. 1 goal, we’re not always going to kill weeds, so we have to keep No. 1 in mind here,” he says.

Good coverage is required for a good weed kill, and good coverage requires smaller droplets that could lead to drift, says Wolf.

Two big conflicts

“So we’ve got two big conflicts in that process, because it takes good coverage to kill weeds, and the good coverage we may want to provide could lead to drift issues.

“This is nothing new — we’ve always talked about it. But we’re moving towards a balance between these two concepts that’s going to be dictated by the label, and it’s going to be more difficult for some than for others to fit that into your spray program.”

Some commercial booms are 120 feet long because there’s a lot of ground to cover and because timely applications are important, says Wolf.

“Whether you’re a self-applicator as a farmer or a commercial applicator, the goal is timely applications. If we do not have good coverage, there will be less weed control, and if we drive faster, there’s more potential for drift.”

There are three critical goals involved in the application process, and it’s important to keep these goals balanced, wherever you might be in the application chain, says Wolf.

“At some point in time, you have to balance these perfectly to get the best job done for the money you’re spending for the product.”

Many farmers have never sprayed anything but glyphosate, says Wolf.

“That has become the ‘easy’ button. We can do it anytime, anywhere and anyhow. But since then, we’ve seen the advent of weed resistance. A resistant weed plant can produce millions of seeds in a year, and even if only 10 percent of them live, it can be a challenge.”

Unfortunately, if it’s not in your field, then you’re probably not worried about it, he says. “That’s the concern we have in the industry. We need to be concerned about it, whatever the product.”

Commercial sprayers, says Wolf, can cost more than $400,000. “If I ran a co-op and owned one or two of those machines, my No. 1 goal would be to cover a lot of acres and to do it fast. But at a grower level, you can invest a lot less in a sprayer.”

From what we know about the new chemistry formulations for dicamba and 2,4-D, airplanes will not be part of the label for those products, says Wolf.

“I don’t know how many years that’ll be for, but for now, they will be applied only by ground. Airplanes, however, do play an important role in other applications. A top-of-the-line ‘air-tractor’ plane could cost as much as $1.5 million.”

Have similar components

But regardless of the sprayer system, most all of them have similar components, says Wolf.

“The one I want to give a lot of attention to is the nozzle. I don’t care if the machine costs $1,000 or $43,000, the nozzle is what gets it done.

“There are a lot of technologies that work to make it happen better, but the nozzle is the key. The one other most important part of that system is the operator — the person driving the machine. The more operators-applicators we can train, the better off we’ll all be in this business.”

Looking at new technology for sprayers, Wolf says flow back valves allow pressure from the boom lines to be relieved back to the tank when the valve is switched to the “off position.”

“Flow back is a current technology by TeeJet. If an airplane is flying over a field to spray a crop-protection product, when the pilot comes to the end of the field, he has to shut it off because he’s turning out onto roads and other fields.

“In a ground sprayer, when you turn off the master switch, it’ll continue to spray until the pressure drops in the check-valve — then it’ll stop.

“If you’re spraying at 40 psi, you’ll have spray down to about 10. Think about that in terms of crossing waterways or other areas that you don’t want sprayed.

“Flow back is a simple design modeled after that airplane system. There’s a hole in the ball valve that flows through to the boom. When you shut off the switch, the ball rotates and seals it.

“All the pressure trapped in the boom will go out through the nozzle. With this flow back, it goes back into the tank. This technology is not found on a lot of our commercial systems, but TeeJet has it available for smaller-system sprayers.”

Wolf says he hears from applicators all the time that they want one nozzle that’ll do everything they want it to do.

“But it’s not going to happen because of the challenges of the droplets, the coverage, and the drift, and the fact that you’ll be spraying something other than straight glyphosate all the time.

“It’s pretty easy to set up straight glyphosate in the tank, going 10 to 12 gallons per acre. If you add other products into the tank, and if you switch back and forth between products that are 10, 15 or 20-gallon, the same nozzle cannot do the job.”

There are stackable nozzle bodies that’ll help with this, he says.

Also in the last few years, there has been a lot of interest in electronically controlling the nozzles on and off. Normally, they are turned off the boom at the control valve.

Auto-steer is pretty much the trend in the commercial spray market today, says Wolf.

“There’s also automatic boom section control which gives you GPS control over the system to turn it on and off. If you tie this technology in with the TeeJet fast-closing back flow valve, you can shut off when you cross that water with an angle to it.”

Most effective in uneven fields

Automatic boom height control is most effective in fields with terraces or uneven surfaces, says Wolf.

“If you spend $430,000 for a sprayer, you don’t want to be moving it around very quickly. But it might not always be a good idea to raise the boom height and increase your speed.”

Air-assist is a technology that has been sold for several years, he continues.

“One of the focuses was to create an air stream to help get the product into the target. The only place where I can see that doing you any good is where you have dense canopies, like with wheat or barley.

“In soybean rust studies, we had just as good effects spraying straight down with a standard-type nozzle.”

Electro-static spraying, explains Wolf, is designed with very small droplets. If the droplets are too big, they won’t function. “They really soak all sides of the leaf, but they won’t get down into the canopy. If you use it for aerial fungicides, they promote 1 gallon per acre, but there’s not a label that supports that.”

Hooded sprayers have come and gone and are coming back, he says.

“I did some work a few years ago in Roundup Ready cotton. The challenge with cotton producers in going back to hooded sprayers is to get that product down in there and get those weeds covered.

“There’s more interest in it now, but it’ll slow down the application process dramatically, and there have been questions about how safe and effective the hoods are.

“With the ones I’ve tested, it has been a challenge to get those nozzles arranged to do the job right. In some cases, you could build up pressure under the hood and that’ll leak. If the hood isn’t well-designed, pressure could build up, and it has to go somewhere.”

The SpotOn sprayer calibrator at some point in time probably will replace the calibration container, says Wolf.

“It’s about $150. But in a 30-second test, my students were able to calibrate three nozzles in the same time as opposed to one nozzle using the cup method.

“It’ll give you a number in gallons per minute. In most low-volume applications, we have found this tool to be very accurate.

“Not everyone calibrates, and not everyone calibrates as they should. But when you do, you want to make sure that the amount of product that the label requires is coming out of the spray machine. You need parameters for your rate control to be effective.”


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About the Author(s)

Paul L. Hollis

Auburn University College of Agriculture

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