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Careful cleanouts

A triple rinse with water may be sufficient for cleaning out pesticide containers before they're recycled, but it won't be enough for cleaning out a sprayer when you're switching crops. And sometimes you can end up with tank contamination even when you think you're using the right cleaning procedure.

"I thought I did a very complete job of cleaning my sprayer after 4,000 acres of Steadfast/Callisto/atrazine. When I cleaned the sprayer, I used CleanOut, an ammonia-based tank cleaner. I took all the nozzles off and sprayed a couple hundred gallons of water out the boom sections," wrote a participant in the Crop Scouting discussion group on Agriculture Online™ last summer.

"Now anytime the sprayer sits for more than a couple of hours, I have to waste 10 to 15 gallons of spray that's in the booms, or I badly burn the beans," he added. This grower later determined that there was chemical remaining in the 4-inch sections between the last nozzle and the ends of the booms.

His situation isn't unique. Sprayer contamination when switching crops continues to be an issue -- especially with certain herbicides or when you're switching to highly sensitive crops.

"I think it's a big problem. We run into dozens of cases of it every year," says Bill Johnson, Extension weed scientist at Purdue University. "The most common issues we see are glyphosate damage to non-Roundup Ready corn and dicamba damage to soybeans."

The problem, Johnson says, is the increasing number of acres that farmers and custom applicators are trying to cover. "I think it's a time issue and people not wanting to take the time to clean the sprayer when they switch crops," he says.

"It takes a couple of hours to clean out a sprayer properly. You need to go through two or three rinses, use tank cleaners, and make sure you get all the sumps and ends of the booms empty," Johnson adds.

"As spray equipment has gotten larger, it tends to have a lot more residual spray material hanging up in the machine compared to 10 years ago," says Andrew Thostenson, pesticide coordinator at North Dakota State University. "If you have a 500- or 1,000-gallon tank, studies have indicated that you can have as much as 6 to 10 gallons of spray material hung up in the system."

Photographs: Mike Holmberg

A triple rinse with water may be sufficient for cleaning out pesticide containers before they're recycled, but it won't be enough for cleaning out a sprayer when you're switching crops. And sometimes you can end up with tank contamination even when you think you're using the right cleaning procedure.

Carl Roberts, Belmond, Iowa,
found there was chemical
remaining in the 4" sections
between the last nozzle and the
ends of the booms in his
sprayer. His situation isn't
unique.

While sprayer contamination remains an issue if you're in a corn/soybean rotation, the potential for problems magnifies if you have sensitive crops such as cotton, sunflowers, canola, alfalfa, or sugar beets in your rotation.

Cleanout procedures vary from one herbicide to the next so you really need to follow the instructions on the label of the product.

Cleaning a sprayer is a whole lot easier if it has a wash nozzle built into the top of the tank, says Vern Hofman, Extension ag engineer at North Dakota State University. "A lot of times the solutions you put in the rinse water don't effectively reach the top of the tank. We have a publication that shows how you can build your own, but most of the new sprayers are coming with the rinse nozzles built right in.

"You can get contamination from all parts of the sprayer," says Dallas Peterson. "The filters and screens may be as big a culprit as anything else because the chemical hangs up in them. A good thorough cleaning should include removing the filters and screens and cleaning those with the same cleaning agents you use to clean the tank."

"There is no better tank cleaner than Roundup. If you let it sit for too long, it can pull chemicals out of a polytank that a tank cleaner didn't." -Mark

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