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The right order

You've likely heard the Las Vegas advertising catch phrase, “What happens in Vegas, stays in Vegas.”  There's a twist on that line when it comes to mixing spray solutions. Mixed properly, pesticides, adjuvants, and drift-reduction additives pass flawlessly from the mixing vat and inductor into your sprayer and onto your crops. This minimizes field trips and off-target movement while maximizing pest control.

Or not.

What happens in your sprayer tank may not stay that way. “Anytime you put something in the tank, it changes the dynamics of the spray solution,” says Jim Reiss, vice president of agricultural chemistries at Precision Laboratories.

Remember the old compatibility test of the Mason jar and kitchen spoon? That's when farmers poured a sample of spray mix ingredients into a Mason jar and mixed it with a spoon. If the mix mimicked jelly or curdled milk, that meant it was added in the wrong order or was incompatible. If the mix and mixing order were right, the ideal form would range from milky white to clear or translucent.

Jelly recipe

Nowadays, applicators have swapped the Mason jar for mixing inductors that convey the mix to the spray tank. Unfortunately, compatibility testing is a lost art, says Reiss. Too many applicators just dump products into the inductor with sometimes terrible results.

Suppose you want to add a little zip to glyphosate in order to control some tough weeds in corn while minimizing drift. Here's the mix and the order of herbicides and adjuvants you pick:

  1. Roundup PowerMax
  2. AgriStar 2,4-D LV 4
  3. Atrazine 4L
  4. Border Xtra 8L

Since the glyphosate product, Roundup PowerMax, is the main product, you'd think that would be the first product in the inductor, right?

Wrong.

“It actually would look OK until you added it to water,” says Reiss, “Then it would start gelling as it entered the sprayer.”

Here is the right order:

  1. Atrazine 4L
  2. Border Xtra 8L
  3. Agri Star 2,4-D LV 4
  4. Roundup PowerMax

Adding chemicals separately is also key, since improperly mixed gelled products clog sprayers. “Inductors are meant to be giant funnels, not mixing vats,” points out Reiss.

What it costs you

Sprayer ownership has many advantages. “That way, I'm not waiting for someone else to do it,” says Scott Church, who farms with his son, Jared, near Catlin, Illinois. It enables you to get the most out of good weather conditions for spraying and to shut down during suboptimal weather.

However, sprayer ownership means mixing your own spray products. That's why the Churches have been working with Reiss and Chad Barnes, an Illini FS sales representative, to develop better spray mixes and to boost their spraying-season efficiency.

Improper mixes cost time and money. Reiss points to a Southern Illinois University analysis showing that a day of downtime at a 400-acre-per-day spray rate leads to lost revenues of $9,600. That assumes 2-inch daily weed growth that clips soybean yields by 2 bushels per acre at $12 per bushel. Higher prices mean heavier losses, Reiss adds.

One at a time

It's also important to spray pesticides one type at a time.

“We now have scenarios where people want to mix herbicides, fungicides, and insecticides together,” says Bob Wolf, co-owner of Wolf Consulting and Research, Mahomet, Illinois. “That is something I never recommend.”

That's because each chemical class may differ in optimal droplet size. A glyphosate and fungicide mix for simultaneously controlling weeds and early-season diseases may save time short term, but their optimal droplet sizes won't click.

Glyphosate works best when applied in a very coarse droplet. This ranges in size from 401 to 500 microns, about the thickness of a staple. Since it's a systemic herbicide, glyphosate moves through a weed at contact. That nixes the need for coating the entire plant. Large droplets also aren't as prone to move off target.

Meanwhile, fungicides are contact pesticides that require fine droplets to evenly coat and to protect a crop. Although the fine droplets ensure crop protection, they are also prone to drift. Their width hovers around 150 microns, about the size of sewing thread.

You can't have it both ways. For optimal efficacy and minimal off-target movement, Wolf advises that you apply each pesticide class separately.

So how do you do it?

Making sure you have the right mix in the right order is easier with a free app that Precision Laboratories has developed. (To download it, go to http://www.mixtankapp.com.) The Mix Tank 2.0 app works on Android and iPhone smartphones.

Mix Tank 2.0 has a database of more than 1,100 crop-protection products from over 17 manufacturers, and it continues to increase in size. The app is designed to assist applicators with the proper tankmixing sequence and to maintain accurate spray logs for record keeping.

“This tool is easy to use and helps prevent application problems, saving time, money, and resources,” says Dan Ori, marketing manager for Precision Laboratories.

“Mixing sequence does matter,” says Reiss. “There's a right way and a wrong way to do it.”


Learn how to mix chemical combinations

Jim Reiss gives a mixing demonstration at www.agriculture.com/efficiency.

Editor's Note: Crops Technology Editor Gil Gullickson produced this story.

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