Math for Pesticide Applicators

These instructions describe how to use the Jar Test Proportions Calculator Excel spreadsheet tool to perform a tank-mix compatibility test, also called a jar test.

1. Download the file linked above.
2. Open the file JarTestProportionsCalculatorAccessible.xlsx using a desktop version of Microsoft Excel. The file should appear in your “Downloads” folder after you download it.
3. Determine your spray volume. Spray volume is the total amount of finished spray mixture (including carrier water) you apply per unit of area. We express spray volume in gallons per acre (gal/acre). Some pesticide product labels list a minimum or maximum spray volume allowed. For tank mixes, select a spray volume that adheres to all labels' requirements. Proper calibration of your spray equipment is necessary to achieve a specific spray volume.
4. In the spreadsheet, select cell B3. A dropdown arrow will appear to the right of the cell. Click the dropdown arrow and select the spray volume you have chosen for your application (in gal/acre). Selecting a spray volume will tell the spreadsheet what number to put in the Conversion Factor column (column E).
5. Determine the formulation type for each pesticide product you intend to tank mix. If you are unsure of a product's formulation type, contact the product's manufacturer using the phone number listed on the product label. In column B of the spreadsheet, under the “Product name” heading, type the name of each product in a row corresponding with its formulation type in column A. For example, if Product A is formulated as Water-Dispersible Granules (WDG), type ‘Product A’ in cell B15. If Product B is also a WDG formulation, type ‘Product B’ in cell B16. If Product C is an Emulsifiable Concentrate formulation, type ‘Product C’ in cell B21.
6. Determine the application rate for each pesticide product you plan to tank mix. In columns C and D of the spreadsheet, enter the application rate per acre for each product in the same row as the product's name. Enter a number in column C, then select the unit of measurement in column D. For example, if a product label says to apply 2 pounds of Wettable Powder per acre, you would enter ‘2’ in cell C13, then select cell D13, click the dropdown arrow that appears, and select “lb/acre”.
   Some labels give the application rate as an amount per 1,000 square feet instead of per acre. If this is the case, enter the amount per 1,000 square feet in cell B5, then click into any other cell. The rate you entered now appears as an amount per acre in cell B6. For example, if Product A has an application rate of 4 ounces per 1,000 square feet, enter ‘4’ in cell B5. Cell B6 will then tell you that your rate is equivalent to 174.24 ounces per acre. In Product A's row, enter ‘174.24’ in column C, then select “oz/acre” in column D.
7. Once you have entered a product's application rate, columns F and G will show you the amount of the product required for 100 gallons of spray mixture. Likewise, columns H and I will show you the amount of the product required for a 100-milliliter (mL) test bottle. Remember, liquid products are measured by volume, while dry products are measured by weight. Therefore, amounts in columns H and I are given in mL for liquid products and milligrams (mg) for dry products.
8. Perform your tank-mix compatibility test. A 100-mL bottle will serve as your spray tank. Measure out your liquid products with 1-mL pipettes; measure out your dry products using a small scale. Follow any pesticide label guidance on mixing and loading products, such as “Fill tank halfway with water before adding product,” or “Agitate until completely dispersed.” Mixing order is critical: Add products to your test bottle in the order you have them listed in the spreadsheet. For example, if you plan to tank mix a Wettable Powder (WP) product and an Emulsifiable Concentrate (EC) product, you would add the WP product to your test bottle before the EC product because Wettable Powders are before Emulsifiable Concentrates in the spreadsheet. If a product label recommends a mixing order different from the spreadsheet, always follow the label. When performing a compatibility test, wear all personal protective equipment (PPE) required by the product labels for a mixer or loader.

Note: This test will show any physical incompatibilities among tank-mix partners. However, it will not show potential chemical incompatibilities. To check for chemical incompatibilities, apply the test mixture to a small area of the target crop or site and watch it for several days to ensure unwanted injury does not occur.