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Scientists Study Chemical Sprayers To Reduce Drift and Improve Application

posted on May 25, 2012

Scientists Study Chemical Sprayers To Reduce Drift and Improve Application

Wind can have an impact on the livelihood of farmers.  It can dry out crops or erode topsoil, but it also impacts farmers when they are applying chemicals to crop fields.  To better understand that impact, researchers have brought the wind inside.

As an electric engine revs up, Greg Kruger, a Crop Systems Specialist with the University of Nebraska – Lincoln, explains the set up.

Greg Kruger, University of Nebraska: "At the far end, we have an axial flow fan and that creates an air flow.  Then we’ve got an air straightener, or a honeycomb that gets that air flow going straight down the wind tunnel.  And we’ve set up a single nozzle sprayer inside this four foot by four 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.

The sprayer sends water through the tunnel.  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.

Greg Kruger, University of Nebraska: "We know that the smaller the droplet size, the greater the drift potential.  The small droplets take longer to reach the ground.  So anytime, we’ve got an air flow that’s pushing those droplets, if it takes longer to get to the ground, it’s gonna' move farther from the point where it was released.  So with our applications and what we do with the applicators is try to get them to use nozzles and pressures and spray solutions that are gonna' give them larger droplet size so that we get more of those droplets at the intended target."

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 usually means smaller droplet size.

Greg Kruger, University of Nebraska: "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.  So there’s a sweet spot in there where we’re trying to hit so that we don’t have a lot of drift, but yet we’re still getting the control from that pesticide that we want."

Near the fan in the wind tunnel is a honeycomb shaped attachment which keeps the 15 mile per hour 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.

Greg Kruger, University of Nebraska: "Anytime something crosses that laser beam, it changes the angle of that light that the lens picks up.  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.  The precision is much better than even we could get with the naked eye.   The diameter of a human hair’s about a hundred and forty microns.  We’re picking up about a tenth of a micron on that laser beam so about 14 hundred times smaller than what the diameter of a human hair is, is the size of the droplets that we’re picking up."

Kevin Wemhoff, Vantage Agri Service: " Wind is probably our largest challenge just due to the fact of the sensitive stuff around you, neighbors, sensitive crops, vineyards."

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.

Kevin Wemhoff, Vantage Agri Service: "Technically by most labels, its 10 MPH, obviously there are many, many days in Nebraska that it’s over 10 MPH. So trying to work within those parameters becomes extremely difficult, yea 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 to reduce drift and there are numerous types of nozzles to choose from to try to keep particle size larger.

Kevin Wemhoff, Vantage Agri Service: "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."

While technology and information have improved efficiency, Wemhoff says it’s still important to continue to get better.

Kevin Wemhoff, Vantage Agri Service: "With more acreages where we are relatively close to some urban areas, Lincoln, Omaha, some other places there are more …vineyards, there are more acreages, people that have moved out of town that you need to be more sensitive to. 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."

That’s what Greg 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.  It can create winds up to 200 MPH to replicate aerial chemical spraying.

Greg Kruger, University of Nebraska: " We’ve got engineering meets physics meets biology…

After some initial testing, Crop Systems Specialist Kruger will put plants in the wind tunnel for further research.  He hopes the work will aid in drift reduction technology something the Environmental Protection Agency is already focusing on. 

Greg Kruger, University of Nebraska: "We’re all familiar with the going and buying an appliance that has an Energy Star logo and what means.  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."

For Market to Market, I’m Perry Stoner.

Tags: chemical application chemical drift pesticide drift university of nebraska