There's something fishy about University of Nebraska's Bob Klein's ideas on how to do a better job spraying for weeds. He thinks you should start by breaking out your tackle box.
The only "whopper" in this story, however, is the difference it will make in your weed control. By simply sliding a couple of plastic utility tackle boxes with molded dividers under a spray nozzle, you can test to make sure it's putting out an even pattern.
The test works best for band tips. But, with extra tackle boxes, it can work for broadcast nozzles as well.
There's nothing new about sprayer calibration. But it has become more critical as farmers use herbicides that offer less crop tolerance, according to Klein.
When Klein gets farmer phone calls complaining about either crop damage or lack of weed control when using band treatments, he asks about the spray tips used when the herbicide was applied. He isn't surprised when he finds nozzles that are either worn or simply the wrong tips.
"One farmer had reported some severe crop damage in a field where he banded herbicide over the row at planting," says the extension cropping systems specialist. "When I checked the tips, he was using broadcast nozzle tips instead of the even-flow tips. Broadcast nozzles concentrate more of the herbicide in the center of the pattern, so he was dramatically increasing the application rate of the herbicide over the row."
Just buying new nozzles isn't the answer, either. In testing units right off the shelf, Klein has found spray pattern distortions that would cause uneven herbicide applications.
"It's just like buying a new car or pickup," he says. "They aren't all perfect."
Klein recommends that you start each spring with two new sets of nozzle tips, a couple of cleaning brushes and a few extra nozzle tips. Before you head to the field, test both sets of nozzles - make sure they're within 10% of their rated output and have a good pattern.
"I wouldn't even waste my time with brass nozzle tips. They wear too fast and distort the pattern and flow rate increases," Klein says. He recommends that farmers use only stainless steel or hardened stainless steel even-flow tips for banding. He prefers color-coded nozzles so it's easy to check that they're all the same on the sprayer. Also, he prefers wider-angle nozzles (like 95 degrees instead of 80 degrees) for banding.
"It might help to set up a test stand in your shop where you can test nozzles one at a time," Klein says. "It's not that hard to do with a 12-volt pump like the ones used for yard sprayers, a pressure gauge and a T controller with valves. You can easily check the output of each nozzle and its spray pattern at the same height that you'll use in the field."
Whether you test nozzle tips in your shop or on your equipment, Klein likes using tackle (also called utility) boxes as a quick check for even application.
"They're cheap and easy to use," he says. "You need to buy the ones that have solid dividers so the fluid can't leak from one section to another. Usually it takes two of them to cover the width of the even-flow nozzle pattern."
Before you slip in the new set of tips, Klein recommends that you check pressure at each nozzle with a liquid-filled pressure gauge mounted on a nozzle body quick coupler.
"If the pressure isn't even at all nozzles, check for restrictions in the lines," he says. "Or, you may have to equalize the length of the lines leading to the nozzles."
Make sure you test the nozzles in the pressure range you'll most likely use in the field, Klein cautions.
"It doesn't make any sense to test the nozzles at 40 psi if you're going to run them at 20 psi in the field," he says. "Also, you need to make sure that you do not ask your spray controller to adjust pressure outside the nozzle's range by too much change in speed."
Once you get to the field, make sure the nozzle height remains the same.
"You can't get accurate application if you test the nozzle patterns on a solid surface and then run the machine in soft soil," Klein says. "You may need to adjust nozzle height on your planter each time you change planting depth. It's also important that you continually use the nozzle brushes to clean the tips. If you don't, material will build in them and distort the pattern."
After a few days of spraying, Klein recommends that you pull the first set of nozzles and replace them with the second set that you've already checked.
"You can retest the used ones and, if they're still good, put them back in," he says. "It's a good idea to keep a few extra nozzles around as well. In the middle of the season, your dealer may not always have the exact tip you need."
Because weeds are No.1 in reducing crop yield, the extra $25-75 you spend on nozzle tips to improve weed control usually is money well spent.
For broadcast herbicide applications, Klein prefers wide-angle nozzles mounted for 100% overlap.
"It makes your spraying as forgiving as possible. If a nozzle plugs when broadcast spraying, you've still got 50% rate," he says. "It also helps with uneven terrain. Sometimes if you start with just 30% overlap, you end up with zero or even underlap in rough fields.
"I also like to tip the nozzle back not more than 30 degrees on broadcast applications," he says. "You can then lower the boom so there's less drift and you get more uniform chemical deposition on the weed surface in postemergence applications." ?