Who’ll stop the wind?


April 25th, 2012

North Platte, NE – For many in Nebraska, wind is merely an occasional nuisance. But for farmers, it can have an impact on their livelihood.

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Wind can dry out crops or erode topsoil, and it can also interfere with the chemicals of farming.

“Wind is probably our largest challenge, just due to the fact of the sensitive stuff around you: neighbors, sensitive crops, vineyards,” said Greg Kruger, a crop systems specialist with the University of Nebraska-Lincoln. To better understand how wind affects chemical drift, researchers have brought the wind inside.

As an electric engine revved up, Kruger explained the set-up.

“At the far end, we have an axial flow fan and that creates an air flow,” he said. “Then we’ve got an air straightener, or a honeycomb, that gets that air flow going straight down the wind tunnel. We’ve set up a single-nozzle sprayer inside this 4-foot by 4-foot wind tunnel. And then back behind that, we’ve got a scrubber system, which will pull out all the particles and air that we’ve generated from running that sprayer system inside that wind tunnel.”

A wind tunnel in North Platte operated by the University of Nebraska-Lincoln Extension seeks to improve spraying conditions on farms to avoid chemical drift. (Photo by NET News)

The sprayer sends water through the tunnel, which is located in a renovated swine barn at UNL’s West Central Research and Extension Center in North Platte, Nebraska. Kruger and his team are trying out dozens of nozzles, searching for the most efficient and effective chemical application methods. It starts with the droplet size coming out of the nozzle.

“We know that the smaller the droplet size, the greater the drift potential. The small droplets take longer to reach the ground,” he said. “So anytime we’ve got an air flow that’s pushing those droplets, if it takes longer to get to the ground, it’s going to move farther from the point where it was released.”

Chemicals are designed to keep crop diseases and pests in check. The research is also investigating how much pressure is ideal for application. The more force used to apply chemicals, typically the smaller the droplet size.

“We’ve done a lot of work in the field looking at different droplet sizes on the efficacy side, and if we get those droplets too large, a lot of times the pesticides don’t work,” Kruger said. “So there’s a sweet spot in there so that we don’t have a lot of drift, but yet we’re still getting the control from that pesticide that we want.”

A nozzle is tested at the wind tunnel. (Photo by NET News)

Near the fan in the wind tunnel is a honeycomb-shaped attachment that keeps the 15-mph wind blowing as straight as possible. This introduces an element of physics to the tunnel and accuracy to the measurements: Each droplet sprayed in the tunnel is measured when it bends the light of the laser beam set up at the opposite end of the tunnel.

“Anytime something crosses that laser beam, it changes the angle of that light that the lens picks up.” Kruger said. “So depending on how far that light bends, the lens knows how, or the lens sends that information to the computer. The computer determines how big the droplet size is. Now kind of counter-intuitive, the more that light bends, the smaller the droplet is. So it’s a little bit opposite of what we would generally expect.”

Using the laser beam and computer allows for great precision in measurements.

“The diameter of a human hair is about a hundred and forty microns,” he said. “We’re picking up about a tenth of a micron on that laser beam, so about 1,400 times smaller than what the diameter of a human hair is, is the size of the droplets that we’re picking up.”

The research is right on target for Kevin Wemhoff. He owns Vantage Agri Service in Otoe County in southeast Nebraska. Applying liquid chemicals makes up a large part of the business, especially this time of year. It’s windy this time of year, too, and chemical application directions don’t allow for much wind.

“Technically by most labels, it’s 10 mph,” he said. “Obviously, there are many, many days in Nebraska that it’s over 10 mph, so trying to work within those parameters becomes extremely difficult. You try to do the best that you can with the challenges in front of you between weather and crops, and when guys are planting, and how much you have to do.”

Wemhoff’s high crop sprayer looks like a large transformer toy, as the boom unfolds to a span of 90 feet. On board, sonar automatically adjusts the height of the boom to the rolling hills for optimum efficiency. There are other options to counter the wind, too. Drift-retarding additives can help weigh down chemicals, and there are numerous types of nozzles to choose from to try to keep particle size larger. Wemhoff points out one on the sprayer boom.

“The blue one on the bottom is a drift guard nozzle, which is one of the ones that helps maintain the micron size of the product as it comes out,” he said.

While technology and information have improved efficiency, Wemhoff said it’s still important to continue to get better, especially for acreages that are close to urban areas or vineyards.

“You are always looking for more data, more information on how far particles move to give you the best idea of how to handle a field,” he said.

That’s what Kruger hopes will come from the research at the new wind tunnel facility in North Platte. In addition to the machine that blows at 15 mph, a much larger machine can be attached, capable of winds up to 200 mph to replicate aerial chemical application.

“We’ve got engineering meets physics meets biology,” he said.

After some initial testing, Kruger said he’ll put plants in the wind tunnel for further research. He hopes the work will aid in drift-reduction technology, something the United States Environmental Protection Agencyis already focusing on.

“We’re all familiar with the going and buying an appliance that has an Energy Star logo and what that means,” Kruger said. “It means that we pick up that product off the shelf and it’s an energy-efficient appliance. Similarly, this DRT policy will have labeling on products so that applicators, when they pick up a nozzle or they pick up a drift-reducing adjutant off the shelf to use with their application, they’ll know that that product will have the ability to reduce drift.”

Kruger says in the controlled environment of the wind tunnel, more precise research can occur since they aren’t working in variable conditions outside. In the end, he hopes the research will help with efficiency on the farm.

“When a farmer goes out and purchases a product and sprays it on his field, he’s purchased that product to control a pest. So if we have drift going off the field, that’s product that he’s lost and he’s not getting the value that he paid for that product from it.”

Kruger said the research could also help with the concern Wemhoff has with an increased amount of ag land and sensitive areas in close proximity.

“There’s a lot of different potential harmful effects that can come from a pesticide moving off target,” Kruger said. “And not every pesticide’s the same, certainly. There’s some that are much safer than others. So making sure that we don’t have that off-target drift or off-target movement of those pesticides is critical to maintaining environmental and human health safety.”

The wind tunnel in North Platte is only the second of its kind in the U.S.

Editorial note: This report is part of NET’s science and environmental reporting project, QUEST Nebraska.

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