May, 1999

Order in The Tank!

David M. Kopec, Extension Turfgrass Specialist

When's the last time you spent some time in the tank – the spray tank that is! Sometimes it's highly convenient to include more than one product in a spray tank mix. For example, two herbicides, two fungicides, or a herbicide mixed with iron, or a liquid fertilizer.

In order to make a successful tank mix, there are two things you should do first. One is to determine if the products are compatible (perform a compatibility test) and second, follow the proper mixing order for product formulations.

I. Compatibility Test

Sometimes a "mixture" of two or more products may not mix well, even though each product alone can be easily sprayed from the spray tank. By performing a compatibility test you can avoid making "jello" in the spray tank. The jello is the result of two products which when included together do not dissolve or suspend in the tank with water. Here is what you need for a compatibility test.

· Two 1 quart jars
· Set of teaspoons
· Sample of the undiluted (store brought) products
· Pesticide(s) to be tested
· Fluid fertilizer or liquid nitrogen to be tested
· A compatibility agent

Mark one of the quart jars with tape as "without agent" and one marked with tape as "with agent." Follow the instructions below in order.

1. Add 1 pint of fluid fertilizer or iron to each jar.
2. Add the compatibility agent to the jar marked "with". Shake the jar gently for 10 seconds.
3. To EACH jar add the proper amount of the pesticide(s) from Table 1. Shake both jars for 10 seconds.
4. Let both of the jars sit for 5 minutes.
5. Look at the contents of the jars and see if there is any signs of flakes, sludge or gels which have formed. Look for any separation layers or small oil particles which formed within 5 minutes. If any of the above occurs in the "without" jar, but not in the "with" jar, you need to use a compatibility agent. If any of the above occurs in the "with jar" then the combination is not compatible and should not be mixed in the spray tank.
If after 30 minutes of sitting (after the shaking) layers are present, but can be re-suspended after another 10 second shake, then the mix can still be made. Make sure that the agitation is "on" inside the spray tank.

If there is layering, an emulsifiable concentrate (EC) product will usually float on the top. If there is layering, wettable powder (WP) products will either settle to the bottom or float on top, depending on the density of the liquid fertilizer.

Note: When mixing two herbicides only (no iron or liquid nitrogen fertilizers) you still need to perform the test. In this case, add 7/8 of a quart of water to each jar and then add the proper amounts of pesticides from Table 1 to both jars and perform the rest of the test as before.

Table 1. Pesticides amounts to use for a compatibility test.


Wettable Powder (WP) 1 lb. 1.5
Dry Flowable (DF) 2 lb. 3.0
3 lb. 4.5
4 lb. 6.0

Emulsifiable Concentrate (EC) 1 pint 0.5
Flowable (F) 1 quart 1.0
Liquid (L) 2 quarts 2.0
Soluble (S) 4 quarts 4.0

II. Mixing Order

After you have determined that the products for the tank mix are indeed compatible, the products should be added to a tank ½ full of water with agitation in the following order.

1. Wettable powder (WP)
2. Dry flowables (DF)
3. Flowables (F)
4. Emulsifiable concentrates (EC)
5. Solubles (s) designated as either solubles (s), soluble liquids (SL), or soluble concentrates (SC).

It may be easier to remember the order as, WP - DF - F - EC - S or by remembering the slogan " Why Pay Double For Frankfurters, Especially Come Sunday."

Remember: Always read the full label. Recommendation and/or restrictions regarding thank mixing are usually listed.

Return to Turfgrass Research
[Cooperative Extension] [AgInfo] [UAInfo]

University of Arizona Cooperative Extension
4341 E. Broadway Road
Phoenix AZ 85040-8807
602-470-8086 FAX: 602-470-8092

Issued in furtherance of Cooperative Extension work, acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, James A. Christenson, Director, Cooperative Extension, College of Agriculture & Life Sciences, The University of Arizona. The University of Arizona is an equal opportunity, affirmative action institution. The University does not discriminate on the basis of race, color, religion, sex, national origin, age, disability, veteran status, or sexual orientation in its programs and activities.

All contents copyright © 2004. Arizona Board of Regents.