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‘My sprayer’s a mess’

In the new era of weed resistance, your risk of a plugged tank or boom is climbing

There may be no better phrase that symbolizes agriculture than “timing is everything.” Planting, fertilizing and harvesting are obvious fits, but the term also applies to pesticide applications, planter preparations and seed purchases.

Another area where timing is important is in the mixing of chemicals, although some may argue that it’s more a matter of steps or procedures in mixing and less a matter of timing. That may be true, until a missed step in the mixing results in a sprayer being parked for two days while it’s cleaned out — throwing off a grower’s entire management timing.

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Every year, there are multiple incidents where physical — as opposed to chemical — compatibility issues arise. Chemical compatibility (i.e. the loss of efficacy of a product or crop injury) still happens more often, leading to complaints that mainly get sorted out by ag retailers.

Physical compatibility issues change the physical properties of what you’re expecting to find in the spray tank, and they usually result from growers or applicators trying to improve their efficiency, whether it’s reducing passes in the field or creating new tank mixes, mainly to confound and control resistant weed species.

Whatever the reason, the mess that can be caused by physical incompatibility is often characterized by gelatinous or batter-like accumulations that can clog tanks, filters and screens and can even make their way through the hoses towards the nozzles. At the 2019 Southwest Agricultural Conference, one grower told presenters that the time he thought he was saving by blending his product quickly was time he lost “100-fold” as he cleaned the resulting mess out of his sprayer.

Tank-mixing compatibility used to be more of an issue prior to the introduction of the Roundup Ready (glyphosate-tolerant) system, and in many cases, its use is creating a “back to the future” scenario. As younger farmers return to the family operation, many have known about weed management through an almost exclusive use of glyphosate. That’s driving this remedial of sorts, trying to help growers — as well as some ag retailers — understand why mixing procedures are important and why there’s a need to slow things down on the way to the field.

“With herbicide resistance creating more challenges, the use of tank mixes in both corn and soybean production is needed,” says Chad Anderson, an independent certified crop advisor (CCA) from Brigden, Ont. “The industry is doing a great service in getting out front to remind growers of how important tank mixing order is both from a compatibility standpoint but also for efficacy.”

Compatibility issues can clog screens or filters or they can force you to replace them. photo: Courtesy Rob Miller, BASF

When discussing the heavy reliance on glyphosate in the past 15 to 20 years, Dr. Fred Whitford notes the learning curve required in managing corn and soybeans, specifically because of the reliance on transgenic hybrids and varieties. Whitford is an author of A Guide to Applying the Principles of Compatibility and Mixing Sequence (PPP-122), published by Purdue Extension in September 2018. The 44-page document (found at, contains detailed explanations of the importance of proper mixing, with photos of what happens when those procedures aren’t followed. Whitford maintains that each of the traits used in corn and soybeans requires growers and ag retailers to understand the trait being used and how that can affect herbicide or insecticide use.

“For me, farmers and ag retailers are mixing materials that even the chemists haven’t tried mixing,” says Whitford, clinical engagement professor and director of pesticide programs at Purdue University. “Part of the problem is that they’re assuming that because it’s two liquids or a liquid and a dry that I can put them in the tank and everything looks fine. But that’s not true — if it was, the chemist would have done all of this already.”

Whitford amassed contributions from several university, private and public sector sources. Much of the impetus came out of ongoing discoveries about mixing, or that some poly tanks are inaccurate in their measurements, or that some people don’t realize there’s a difference between a liquid ounce and a dry ounce. And it isn’t just farmers who are rushed for time: Whitford and his colleagues have surveyed roughly 1,000 retailers and found that 90 per cent had issues of physical compatibility.

“We have very limited time to make these applications and if we try to maximize our control, we have to hurry up when the timing is there,” says Whitford. “So you have applicators who are hurrying and it’s not just basic chemicals, it’s accidents on the road, it’s spraying the wrong field — it’s not taking the time to think about it only because we don’t have the time. And I hear that all of the time and say, ‘Okay, do you have the time to clean up the mess?’ because that’s what they’re swapping.”

In the grand scheme of things, spending an extra 10 or 15 minutes paying greater attention to mixing sequences or ensuring half the water volume has been poured into the tank before mixing starts is time well spent. It’s especially true against the one or two days needed for cleaning out the batter-like material, or the cost of replacing parts that couldn’t be cleaned.

“All somebody has to do is think about ‘Cooking 101’ and what could happen if you don’t follow a recipe, and what could go wrong,” says Whitford. “And our chemistries are no different.”

It’s all the more reason for taking greater care and understanding that it’s not just one or two chemistries that are blending together, sometimes there are several inert compounds contained in one product.

Start with the label

Part of the frustration for those in ag retail, and in extension, is that all of the information needed — the recipes and what can be added or how it should be added — is readily available on the label. For Rob Miller, technical development specialist with BASF, the importance of understanding the label and proper mixing order cannot be overstated. True time savings or increased efficiencies will come from knowing what’s on the label and why wettable powders must be added first. For instance, if you put in an oil first and then add the powders, the oil coats the powders preventing water from breaking them down. This can result in a buildup on some of the screens or in the nozzles, and those need to be addressed before they create larger problems.

“You’re not just looking at replacing a couple of filters or rinsing them out, it could be the entire tank,” says Miller. “We’re always gathering new information and water quality is very different as we move across the province and there are various tank mixes, as well. That’s where we have to err on the side of caution and if we’re not sure, we always do a jar test.”

The jar test has become something of a lost art when it comes to tank mixing. Again, the reason goes back to the days of the simplicity and convenience of using glyphosate, where growers perhaps fell out of practice with the jar test. It’s more than just tank mixing different chemistries; the jar test is now of greater value as a resource with more growers trying to add fertilizers or use them as a carrier. Miller says where some growers have added UAN, now they’re also trying to include sulphur in one form or another.

High levels of minerals in water can bind to glyphosate — with distilled water (left) and high levels of minerals in hard water (right). photo: Courtesy Dr. Fred Whitfield (Purdue University)

Anderson agrees that jar testing is probably a new concept to a lot of people, especially those trying to do something a bit different with tank mixes. At the same time, he notes the value of maintaining an open-door on communications with ag retailers as well as chemical company personnel.

“This is where it’s ultra important to have a good relationship with industry representatives,” says Anderson. “Most of us don’t come up with a new idea or mix combination but rather just something that hasn’t been done in our area before. The people who support those products have a vast knowledge and network to help answer any questionable approaches and they can help avoid any serious consequences.”

What is the proper order?

The extension and ag retail sectors have worked hard to bring more information, resources and support. Purdue Extension has its guide and companies including BASF engage with growers and retailers on many different levels, always trying to build relationships and sources of information that help improve productivity and minimize problems.

Miller is a proponent of the acronym WAMLEGS, which stands for Wettable powders (dry ingredients), Agitate (anti-foaming compounds and buffers), Microencapsulated suspensions, Liquid and soluble products, Emulsifiable concentrates, high-load Glyphosates and Surfactants. This acronym replaces the previous form, WALES, which didn’t include microencapsulated suspensions and glyphosates.

“We always want to read and follow the label directions first,” says Miller, noting some labels will have a reverse order, like Liberty (glufosinate) when mixing with another product like Select. “In that case, WAMLEGS doesn’t apply. But that’s where it’s really important to use this term as a guideline: we always recommend that users refer to the label, just in case there are differences.”

An added twist

The use of fertilizer, particularly N-based formulations like UAN, has become relatively commonplace compared to the addition of sulphur which seems to be increasing. Whitford has encountered many growers and retailers adding ammonium thiosulphate (ATS) to their tank mixes, to the point where he’s added micronutrients to the end of his list for mixing.

“All of the work I’ve seen so far says that if you add sulphur anywhere but at the very end, you’re going to mess things up horribly,” Whitford says. “You better do a jar test because sulphur is very reactive in our mixes, but we’re learning the hard way, where people are putting it in and they’re getting this stuff to fall completely out of suspension.”

The best part of a farmer doing their own jar test, he adds, is that they’re using their own water source, with its hardness and pH. Everything is there to make that judgment on a combination that the manufacturer has likely never tested. It’s the farmer’s chance to be the chemist and put it to the test on their own operation.

“When I ask groups — and let’s say it’s 100 people — maybe one or two in any group will tell me they’ve used the jar test, but most people have never used it or they don’t know what it is,” Whitford says. “It’s been on labels forever but we haven’t used it and those who do use it only did because they had a compatibility problem. They’re not doing the jar test to see whether things will mix, they’re using it after the fact and they’re trying to figure out what happened. Spending a few minutes doing a jar test or following some basic mixing procedures actually saves time during the season.”

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