Proper tank mixing is essential to getting the best results from crop products. In fact, if you’ve ever been unpleasantly surprised by the effect of a pest you thought you’d protected against, one of the possible causes may be an error in tank mixing procedure. I’ve met with many growers over the years who have been forced to spend significant time cleaning their sprayer as a result of a tank mix incompatibility issue. In most cases, they could have avoided this problem simply by following a more effective tank mixing method. To avoid frustration and get the best results possible, follow the proven tank mix tips outlined below.
1. ALWAYS READ AND FOLLOW THE PRODUCT LABEL
You’ve heard it before, and you’ll hear it again: always carefully read and follow the product label. Pay attention to things like the mixing order and spray nozzle recommendations. Do not be tempted to ignore any steps or instructions. This is vital to getting the best possible results from your crop protection products.
If the product label does not provide instructions for your specific circumstances, follow the www.WALES methodology below.
2. FOLLOW THE WWW.WALES SEQUENCE
Several years ago, we at Syngenta developed a tank mixing sequence referred to as the www.WALES process to help growers maximize the effectiveness of crop protection products, while ensuring a problem-free application experience.
The steps of the www.WALES process (in order of start to finish) are:
w –Water or liquid fertilizer go into the spray tank before anything else. Fill tank at least one quarter full and start agitation before adding crop protection products.
w –Add products packaged in a Water Soluble Pouch into clean water before any other material is added to tank. These are typically highly potent products, such as sulfonyl ureas, and packaged in small pouch made of a water soluble film.
w –Add Wettable Powders (WP)
W –Add Water Dispersible Granules (WDG)
A –Agitate thoroughly to ensure
dispersion and/or dissolution of solids. Maintain agitation during mixing and spraying. Allow each product to mix thoroughly before adding new materials.
L –Add Liquid flowables –Suspension Concentrates (SC) or Suspo-emulsions (SE)
E –Add Emulsifiable Concentrates (EC) or microemulsifiable concentrate (MEC)
S –Finally, add Solution (SN/SL) type products. Then fill the rest of the tank with water and continue to agitate until completion of spray operation.
3. MAINTAIN A GENTLE AGITATION
Keeping a constant, gentle movement is necessary to thoroughly mix the spray mixture and ensure a consistent, uniform application. Otherwise, any solid or suspended granules of the active ingredient could settle, and you’ll wind up with an overdose of the active ingredient in certain parts of the field, and no application of it in others.
When using granules or wettable powders, all particles must undergo thorough wetting, and be uniformly dispersed in the spray tank — so gentle agitation is required to ensure that the granular products have been thoroughly penetrated and broken down by the water.
Remember that even liquid flowables have suspensions of active ingredients in them, which must be uniformly dispersed. Without agitation, those suspended solids could settle and an uneven application may occur.
4.US EAPPROPRIATEIN-LINE AND SPRAY NOZZLE SCREENS
It is necessary to use the appropriate spray nozzle screen in order to spray effectively. If the screen is too fine, a solution containing coarser particles will block the screen and the active ingredient won’t be properly dispersed or evenly sprayed out. Even if your screen is only partially blocked, the application in the field will be uneven.
Nozzle screen and in-line screen selection depends on the type of formulations that are being mixed in the tank. When using solid formulations (WDG or WP) or liquid flowables (SC or SE) in which active ingredients are suspended, use a coarser screen (25-50 mesh). A finer mesh screen (50 mesh or higher) is more suitable for clear, emulsifiable formulations (EC or MEC) or water-based solution products (SL or SN). When in doubt — or if you are applying both types of solutions — default to a coarser screen.
5. MIX ADJUVANTS IN AT THE RIGHT TIME
Depending on the type of adjuvant you’re using, you will need to mix it either first or last in the tank mixing process. Adjuvant added to improve compatibility must go into the mix first. If it’s added later in the process, you could wind up with either putty-like sediment or an oil-and-water type immiscible mixture. On the other hand, adjuvants used to enhance bio-efficacy must be mixed in last. Typically, these adjuvants contain oil and if added to the mix at the beginning of the process, they could coat the solid particles in the mix and therefore won’t disperse properly.
If an adjuvant is required, don’t take the risk of omitting it. Ensure appropriate adjuvants are used at the right rate and as per the product label. Improper use of adjuvants will slow down the plant uptake of the active ingredients, reduce the activity of the product and could even render it ineffective.
Ravi Ramachandran is the manager of product chemistry and chemical services with Syngenta Crop Protection Canada.