TOOLS AND TECHNIQUES

By Ben Pease , Nick Christians , Ph . D ., and Adam Thoms , Ph . D .

From the previous article ( in April SportsField Management ), we see that tank mixing is a common practice in all aspects of turfgrass management with many benefits : apply multiple chemistries at once ; improve the spectrum of pest / disease control ; make time-sensitive applications ; and , of course , save time and money through reduced labor costs , equipment wear and fuel usage . Tank mixing is much more than just throwing all of your products in your spray tank at once . Proper tank mixing is important because product-mixing order can affect product efficacy , impact turfgrass health , and help avoid costly / timely product incompatibilities .

When preparing a tank mixture , we should be mindful of the following considerations : Are you using a new product ? Are you using a different formulation than usual ? Has your water source changed ? Have you made any equipment changes or upgrades ? These questions and more are a concern because changes or additions to a tank mix could lead to issues known as physical and chemical incompatibilities .

Incompatibilities occur when one product interacts ( negatively ) with another product in the tank mixture . These interactions , also known as synergism , are an interaction of two or more substances to produce an effect greater than the sum of their separate effects . In the case of an incompatibility , this synergistic effect is detrimental to the tank mixture and / or turfgrass health . Indicators of a physical incompatibility ( or synergism ) are layering in the tank , excessive foaming , formation of oily residues , or products that will not dissolve or suspend in solution , usually causing precipitation of products or formation of gel-like solution in the tank or hoses . Indicators of a chemical incompatibility ( or synergism ) are more difficult to recognize . Unlike the visual indicators of a physical incompatibility , a tank mixture with a chemical incompatibility may look normal . Often the symptoms are not evident until hours or days after a spray application , manifesting as turfgrass injury ( phytotoxicity ) or reduced product efficacy . Did you notice reduced disease or weed control ? Tip burn or total injury ? This is likely due to chemical incompatibility , often caused by incorrect use ( or nonuse ) of a surfactant . In cases like this , it is important to check the label for surfactant requirements or environmental factor limitations . It is also important to avoid tank mixing root-uptake chemistries ( need to be watered-in ) with foliar-uptake chemistries .

We can take steps to avoid tank mixture incompatibilities . The first step is always to check the product label . Likely , the label will list products that are compatible and incompatible with the product in question . Of course , it can never be an exhaustive list , so there may also be instructions for performing a jar test . A jar test is a way to test new products within a tank mixture for compatibility issues , but is done on a very small scale ( Figure 1 ). Rather than risking an entire tank mix of expensive product , this uses fractions of ounces ( oz .) of products .

Many labels give you specific mix amounts for conducting a jar test , but , if not , let ’ s examine the math involved . If you have a 300-gallon tank and spray at 40 gallons per acre , your tank covers :

If the product you ’ re testing has an application rate of 64 ounces per acre :

You need 480 oz . of product per tank . To calculate the ounces required for a jar test , we set up a proportion just as we did during sprayer calibration , followed by cross multiplication and division :

This is assuming a 1-quart ( 16 ounces or 0.125 gallons ) container . You will need 0.2 oz . ( or 5.9 ml ) of product to mimic what would be in a full tank mix . Aside from performing a jar test , tank mixture steps and order of product addition play a large role in avoiding incompatibilities .

As was mentioned previously , reading the product label is the first step . The second step is to add at least 50 % of the required total water volume to the spray tank . Third , begin agitation and then start add-

18 SportsField Management | May 2021 sportsfieldmanagementonline . com