Premix vs. Tank Mix Ag Chemicals

What’s the difference?

Tank mix products require mixing in a spray tank prior to spraying, whereas premixes have been specially formulated to be sprayed, no mixing required. Premix products are more convenient, require less handling, and are professionally prepared, but given your soil type or target pest, tank mixes might still be the best choice.

Here are some things to consider when evaluating Premix vs. Tank Mix products.

Premix products may not be ideal for your soil type

For premixes, the ratio of chemicals is prepared for the highest volume of use in a particular region. But for different climates and soil types, the optimal volume is not necessarily the highest volume.

For example, Harness Xtra® 5.6L is a simple combination of 3.1 lbs. of acetachlor and 2.5 lbs. of atrazine per gallon. This combination works well in central Iowa, but not in places where soils need a certain chemical volume to get pre-emergence grass under control without causing atrazine carryover and impacting future soybean rotations.

The makers of Harness Xtra® 5.6L realized this issue and released another premix called Harness Xtra®, which has 4.3 lbs. of acetachlor and 1.7 lbs. of atrazine per gallon. This formulation allowed for more grass control with less atrazine for heavier soils where atrazine carryover is an issue. 

Premix concentrations may create application timing conflicts

When using a premix, application timing is dictated by the ingredient ratios in the mix, which are determined by the manufacturer.

However, the individual pesticides may actually be best suited for different application timings. For example, Spartan Charge® is a combination of Authority® (sulfentrazone), a pre-emergent herbicide, and Aim® (carfentrazone), a post-herbicide.

The combination should stop weeds from emerging before germination and control weeds after they emerge. But by waiting to spray until weeds have emerged to increase the effectiveness of the post-herbicide, some weeds will germinate that the post-herbicide does not control.

Spraying earlier will increase the effectiveness of the pre-emergent herbicide, but more of the post-herbicide will be lost before it can be effective, potentially requiring a second spray. Sometimes the best weed control can only be achieved by applying pesticides separately.

If you decide on Tank Mixes

Tank mixes give a farmer more freedom to customize their chemical mix and be more selective relative to their soil type and ideal application timing.

However, if you choose to tank mix, it is essential to have a thorough understanding of the product guidelines. Tank mixing requires greater skill to mix and handle the products properly, which is important to ensure uniform coverage and effective pest control.

Improper mixing can be costly, particularly if the spray tank becomes clogged and requires the disposal of a spray rig.  

Check for chemical compatibility

When tank mixing products, check the product’s label (you can search for thousands of chemical labels here). The label should contain information on compatibility with other chemicals, but companies don’t test the compatibility of all combinations.

You can perform a simple compatibility test by mixing the products in a small container at planned rates prior to mixing in a full-scale spray tank.

When mixing compatible chemicals, follow this order to achieve optimal mixing. The mixture should be given time to agitate after each step and new addition.

• Wettable Powders

• Dispersible Granules

• Flowables

• Emulsifiable Concentrates  

A few good rules to follow when mixing:

• Mix only what is needed for the day

• Don’t add concentrated chemicals to an empty tank, fill half the tank with clean water

• Start the agitation before adding chemicals

• When rinsing mixing containers, pour the rinsate into the tank - don’t improperly dispose of the rinsate

• Fill the tank to its final volume after all the products have been added

• Properly dispose of all empty chemical containers

The real benefit of tank mixes is being able to choose the ratio of each product to get the best performance based on the unique conditions of your operation.

This improved performance may even justify the cost of two different product applications over a premix product sprayed once at a time that was only optimal for one of the ingredients. 

Harness is a registered trademark of Monsanto Company. Spartan Charge, Authority and Aim are are registered trademarks of FMC Corporation.