Do This Before You Step Foot in the Sprayer

Sally Krueger

Jun 05, 2018

Before you step in your sprayer, you’ll need a bit of prep time to ensure you're ready, and to set yourself up for an effective and efficient spray. Here are few best practices to follow before you make that first spray pass:

1: Know your equipment

That’s why we created a guide on the ins and outs of common sprayer equipment. Before you begin spraying, review the equipment guide. Get to know your equipment, so you can troubleshoot any application issues before you’re out in the field, and keep your sprayer running smoothly for years.

2: Understand tank mix compatibility

It’s common to tank mix chemicals to increase efficiency (i.e. fewer spray passes over the crop). However, the wrong combination of ingredients can leave you with clogged nozzles and/or crop damage. You’ll also want be mindful of the number of tank mix partners you’re using. The more you put in the tank, the more likely active ingredients and formulated adjuvants will be incompatible.

Following a simple tank-mixing order can eliminate most problems you might have prepping your spray solutions.

An easy way to remember the correct order is to use the acronym WALES:

W: It starts with the addition of herbicides starting with W--WP (dry wettable powders) and WDG (water dispensable granules) placed in the tank. Most of these types of products suggest pre-soaking the herbicide in small amounts of water to enable the products to properly dissolve in the spray tank. But always be sure to follow label use instructions for the product.

A: Continue with moderate agitation. Excessive agitation will increase foaming issues and can reduce compatibility. Continue agitating the mix until you’ve completed your spray pass.

L:Liquidor flowable herbicides are added next.

E: Next is the addition of Emulsifiable Concentrates.

S: The final step is Surfactants/Solutions.

Generally, true soluble liquids don’t have much impact on mixing sequence, and they can be added early or late with other soluble liquids. The biggest issue to compatibility is where dry formulations and emulsifiable concentrates (EC) are added in the mixing sequence. If you’re going to be adding a high-load glyphosate, like Roundup PowerMAX®, add it before the final step “S.”

Mixing biologicals

Assuming that most of these materials are formulated as soluble liquids (not an EC or suspension concentrate), add them at the end of the mixing procedure. If they are formulated as dry (WDG, WP, etc.) then they would go in to the spray preparation very early in the mixing sequence. When it comes to living organisms in your biologicals, the tank solution pH should be considered. For example, biologicals prefer a pH close to 7, while rhizobia and mycorrhizal fungi are considerably sensitive to low pH².

3: (When in doubt) Perform a jar test

If you are concerned about tank mix partner compatibility, perform a jar test. Follow the product’s label instruction to perform the jar test.

Steps for Performing a Jar Test

*Perform the test in a safe and ventilated area. Always wear personal protective equipment (PPE) when performing a jar test.


When you hear an agronomist talk about “antagonism,” they’re describing a scientific phenomenon where two or more items mixed together have an overall reduced effect simply from being combined. It’s important to know that mixing two products or ingredients together doesn’t always mean they retain their effectiveness³.

4: Reduce your chances for exposure

There are some basic tips for protecting yourself, and others, while handling pesticides and such. As you probably know, these include wearing gloves and protective eyewear, and also using spray solutions in a well-ventilated area. At a minimum, you also should be wearing a long-sleeved shirt, long pants, shoes, socks and chemical-resistant gloves. This is your standard, go-to personal protective equipment, or PPE.

It sounds like a broken record, but read the product's label. Many labels will require you to wear more than the minimum PPE mentioned above, depending on the product’s toxicity and use.


Adding pesticide to the sprayer can be tricky. For example, some custom applications and operators place dissolvable pouches in the basket so they can be broken up by the hydraulic return or the fill water. But, fill water often splatters out of the basket and the bags can “puff” open, releasing product into the air. This creates unnecessary contamination and exposure².

Once you've done these things, you should be ready to to step foot in the sprayer cab and move ahead to make that next spray pass. 


  1. Pocock, P. (2005, June). Custom Spray Quandary? Retrieved from:

  2. Deveau, J. Tank Mixing Order and the Jar Test. Retrieved from:

  3. Espinoza, L., Norman, R., Scott, B., & Smith, K. (2011). Checking for Compatibility of Herbicide-Fertilizer Combinations. Retrieved from:

  4. Bauer, E., C. O., Hygnstrom, J., & Hansen, P. (2012, August). Protective Clothing and Equipment for Pesticide Applicators. Retrieved from

  5. Enz, J., Hofman, V., & Thostenson, A. (2017, November). Air Temperature Inversions. Retrieved from:

  6. Wolf, T. (2015). Deciding on the Right Way to Spray. Retrieved from:

  7. Armstrong, J. (n.d.) Understanding Herbicide Mode of Action. Retrieved from:

Sally Krueger

Jun 05, 2018