Jar Testing Tips

December 24, 2019

By Jayde Reilly, Agronomy Marketing Manager

According to the University of Arkansas, a “Jar Test’ should always be used to test the compatibility of herbicides with fertilizers. Herbicides and fertilizers are normally tank-mixed to save time and application costs. However, some herbicides may not be compatible with fertilizers or may be affected by the spraying water. Below are some tips for successful jar testing:

Use the W-A-L-E-S Method:

W-ettable powders and water dispersible granules 

A-gitate tank mix throughly 

L-iquid flowables and suspensions 

E-mulsifiable concentrate formulations 



Jar Testing Steps 

  1. Add 1 pint of carrier (water, liquid fertilizer) to 1 quart jar. This ensures there is enough carrier in the tank to accomplish dissolving and getting products into solution. 
  2. Add each product to the jar in the ratio and order that you will add them to the spray tank. Use the W-A-L-E-S sequence when tank mixing. See calculations to the table. 
  3. Fill the rest of the jar with carrier and shake and invert for 30 seconds. Let the solution stand for 30 minutes and then inspect for precipitates, sludges or separations If none of these appear, the mixture is compatible.


9 Tank Mixing Mistakes 

  1. No Test: Operator combines inadequately tested formulations. 
  2. New Mixtures: Operator prepares new mixtures using multiple products. 
  3. Out of Sequence: Operator mixes product in the wrong order. 
  4. Insufficient Water: Operator adds product when theres not enough water. 
  5. Not Dissolved: Operator doesn’t wait until products are dissolved before adding more products. 
  6. Water/Fertilzer: Operator doesn’t consider differences when substitute fertilizer for water. 
  7. Cold Water: Operator doesn’t allow more time for products to mix in cold water. 
  8. Agitated Strength: Operator mixes with too much or too little agitation. 
  9. Label Ignored: Operator doesn’t follow label directions. 


Jar Test Strategy 
Combine the ingredients listed here to determine if a tank mix will save you time and cost of a second application of pesticide
Material Order Material amount add to jar*
Water Soluble Pouches 1 1 Tbs/lbs
Wettable Powders 2 1 Tbs/lbs
Dry Flowables/Water Dispersible Granules 3 1 Tbs/lbs
Suspension Concentrates/Flowable Capsule Suspensions 4 1tps/pint
Emulsifiable Concentrates 5 1 tps/pint
Soluble Liquids 6 1 tps/pint
Soluble Powders 7 1 tsp/lbs
Surfactants Oils, remaining adjuvants 8 1 tsp/pint
Fertilizers 9 1.1 grams **/lbs
*equivalent to underlined unit of pesticide or fertilizer per 100 gallons of final spray solution

**use an inexpensive postal scale to measure this amount

  • Archive