Combining herbicides into a spray mixture can be tricky business, not to mention all of the other complexities with applying product on the farm. But following a mixing order can eliminate most problems encountered in the preparation of spray solutions.
Step 1: Fill spray tank ⅓ full of carrier to be used with tank agitation running. Carriers include water, fertilizer, or combination of each.
Step 2: If a glyphosate product will be used, add ammonium sulfate.
Step 3: Check the herbicide labels for any compatability issues and add compatibility agent at this time if required.
Step 4: Check the herbicide labels for foaming problems and add defoamer as needed. Defoamer is more effective when added prior to foam formation.
The WALES Method
Step 5: The next few steps can be remembered by the acronym WALES. It starts with the addition of herbicides that start 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.
Step 6: Next comes the A in WALES: Agitate. Continue with moderate agitation. Excessive agitation will increase foaming issues and can reduce compatibility. Agitation should continue until the solution is applied.
Step 7: Then there’s the L: Liquid or flowable herbicides are added next.
Step 8: Addition of E--Emulsifiable Concentrates--are next to be added to the spray tank, followed by the final step in WALES: Surfactants/Solutions.
Finishing the Mixing Process
Step 9: All of the planned herbicides should now be in the spray tank. Now is the time to add required adjuvants. These include NIS (non-ionic surfactant), COC (crop oil concentrate), and MSO (methylated seed oil).
Step 10: If drift of spray solution is a possibility, add drift control agent at this time.
Step 11: The last step will be to add additional carrier to total of 100% of spray solution needed. Be certain total spray solution has been properly mixed before application.
Some final tips to remember: Always read and follow the herbicide label directions, and always wear the required PPE (personal protective equipment) when handling any pesticide. It is the law. Not all herbicide combinations may be listed on the label. If you have a concern about compatibility with the mixing of some herbicides, you can conduct a jar test. The herbicide label will describe how to conduct the jar test that will determine if the herbicides can be combined.