Where crop spray chemical goes, clean those

When it comes to cleaning sprayers, the tank is just one target. Here are a few tips for better, faster clean-outs

Ken Munro’s sprayer clean-out strategy is to send tank cleaner wherever the chemical goes.

“We start at the chemical inductor and go from there,” says Munro, who farms and works at Central Alberta Co-op’s Green Way Agro Centre in Innisfail. Just cleaning the tank isn’t good enough.

Sprayer specialist Tom Wolf — @nozzle_guy — echoed this with a Twitter message: “(It’s) important to think of the whole sprayer. Tank, hoses, valves, screens, boom ends, dual-flow plumbing. We found that surface area of plumbing is about one-third of tank wall area. Significant, but can’t see it.”

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Munro is reminded pretty much every year of the value of his complete clean-out policy. In 2015, a Co-op customer of his had been spraying PrePass (Groups 2 and 9) ahead of a cereal crop. The next time he used the sprayer was to apply straight Assure on canola with a grassy weed problem. Interestingly, the damage — which became obvious a few days later — occurred only on the last 10 acres or so of the first tank.

So what happened? “The sprayer had a front load and side load system, and we figure the side load didn’t get flushed,” Munro says. “Once the tank level dropped below the side inlet, the Group 2 residue dropped back into the tank.”

Complete clean-outs can seem like too much time to spend between jobs, but Keith Gabert, agronomy specialist with the Canola Council of Canada, says it’s a job that has to be done. “Herbicide injury caused by sprayer contamination is preventable,” he says. “You just have to take the time.”

Time savers

Set up a clean water source on board the sprayer with its own pump that only ever handles clean water and tank cleaning solution. Then use that clean water source strategically.

“Multiple smaller flushes have proven more effective than one large flush,” Gabert says. For example, two washes with 70 gallons each or three with 30 gallons each are just as effective as a single 600-gallon wash — and use way less water.

Munro uses three small rinses: water, then water plus ammonia-based cleaner, then water again.

“We start at the inductor, cycling clean water through there then to the sprayer. The sprayer cycles that water for 10 to 15 minutes, then we spray it out in the field,” Munro says. “While that is happening, we reload the inductor with water and Finish (cleaning agent) and cycle that in the inductor while the sprayer is cycling the water, and so on.”

Group 2 residue in the sprayer after spraying beans did some noticeable damage to these canola plants.

Group 2 residue in the sprayer after spraying beans did some noticeable damage to these canola plants.
photo: Justine Cornelson

Continuous rinsing

Continuous rinsing is another idea gaining traction in Europe. Tom Wolf and his mates describe the concept in the article “Continuous rinsing” at their sprayers101.com website. Continuous rinsing works like this:

As soon as the tank is empty, the operator switches on the dedicated clean water pump to deliver clean water through the tank’s wash-down nozzles. The main product pump then delivers the wash-down liquid to the boom and return lines.

“Because the clean water pump will deliver less than the boom flow, the cleaning mixture is delivered somewhat intermittently. We are told that this helps with the cleaning action of the lines,” the article says.

Once the clean water tank is empty, the pressure drops again for the final time and the tank rinsate is now very dilute.

Continuous rinsing takes only about half as long as the batch mode, according to testing in Europe. It also uses less water. And, as the article says, “the sprayer never has to stop, and the operator never dismounts.”

While this European technology will need some adjustment for the size of North American sprayers, Wolf does see continuous rinsing as a positive development to save time and water and to take some of the pain out of tank clean-out.

Another time saver is the Hypro Express boom end cap. This is described in another recommended sprayers101.com article called “Top sprayer retrofits.”

The few inches of boom between the last nozzle and the boom end can trap spray water, and Wolf’s research has shown these areas are not easily rinsed clean. That is why many sprayer operators have retrofitted their sprayers with “jobber ball valves” at all boom ends, as Gabert describes them.

Hypro’s Express boom end cap (see below) is an alternative to the ball valves. It allows the last nozzle body to be mounted right at the end of the boom so there’s no extra space for spray water to hide. As a bonus, the end cap also bleeds off any air bubbles in the line. This isn’t really a clean-out issue, but it does improve spray on-off precision — which is particularly useful for sectional control.

Hypro’s Express boom end cap allows the last nozzle body to be mounted right at the end of the boom so there’s no extra space for spray water to hide.

Hypro’s Express boom end cap allows the last nozzle body to be mounted right at the end of the boom so there’s no extra space for spray water to hide.

Other tips to prevent sprayer contamination

  • Spray immediately after filling and spray until the tank is empty. When some herbicides, particularly Group 2s, are left in the tank for extended periods, they can leave deposits that, if not cleaned out well, may come back into the spray solution in subsequent sprays. And some herbicides and their surfactants, Liberty for one, can be very good at lifting herbicide residues from tank walls and sprayer plumbing. The longer such products are in the tank, i.e. during a rain delay or breakdown, the more scrubbing they could do.
  • Look for solid herbicide residue. Some herbicides may precipitate out of solution and many dry herbicides use clay as a carrier. These particles can become trapped in some parts of the sprayer or plumbing. Visual inspection can identify these problem areas and ensure that they are cleaned properly.
  • Check filters and nozzle bodies. Nozzle screens and in-line filters can be a significant reservoir for undiluted or undissolved herbicide and are too often overlooked in sprayer decontamination. Remove all filters and nozzle screens and thoroughly clean in fresh water. Run clean water through plumbing leading to the screens. When rinsing the boom, rotate through all nozzles in a multiple body.To speed this along, Munro keeps a clean set of filters in a five-gallon pail of water and Finish cleaning agent. He puts the clean filters on when clean-out is done, then puts the old set of filters into the cleaned pail for next time.
  • Use a tank-cleaning additive with the rinse water. Check product labels to see which cleaner is recommended. For some, ammonia alone is enough. For some, a detergent (surfactant) alone is enough. For others, a combination of both is required.

How to ID a sprayer contamination issue

It takes days or weeks to identify a spray tank contamination issue because operators rarely notice anything amiss during application. The problem isn’t apparent until plants start to show symptoms. Here are some clues to look for:

  • Misshapen growth. Look for stunted growth on leaves and roots, leathery leaves, twisted stems, clumpy root hairs or otherwise odd root development. Note that these symptoms can also result from herbicide carryover in the field.
  • Patterns in the field. Look for damage that starts off severe then gets progressively less and finally ends after a few sprayer passes. This indicates something left over in the booms and filters that was sprayed out within the first few passes.
    Patterns that clearly relate to this year’s sprayer passes are caused by sprayer contamination, spray conditions or product selection issues. If damage is across the whole field but is lower in corners where the boom moved faster and deposited less product or is lower (or non-existent) in sprayer misses, this indicates a spray tank contamination that affected the whole load.

Note that in some cases crop damage may not occur until the operator uses an active ingredient or surfactant particularly good at scrubbing. This could be many loads after the original contamination.

About the author


Jay Whetter is communications manager for the Canola Council of Canada.



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