Problems with herbicide compatibility are usually the result of poor mixing techniques. Typically, the herbicide products are not pre-wetted prior to inclusion in the spray tank. It is important to pre-wet all products, whether liquid or solid. The general guidelines for herbicide mixing include:
Refer to the specific herbicide label for exact mixing instructions.
Determine compatibility of herbicides and carriers by using small containers rather than large spray tanks.
Pre-wet dry or suspension herbicide formulations, add them to the spray tank, and agitate. Pre-wet herbicides with an appropriate amount of water. This is especially important when fluid fertilizer is the intended carrier.
Pre-wet the EC formulated herbicide, and add it to the spray tank during filling. Agitate during the process.
Include safety equipment that will prevent potential backsiphoning of the spray tank into the well.
Directions vary among herbicides on the amount of carrier to place in the spray tank prior to the addition of the herbicides. Follow label instructions closely. Compatibility agents may be necessary if fluid fertilizer is the primary carrier.
Water temperature is another source of compatibility problems. Cold water may inhibit the proper mixing of some herbicide formulations. This is particularly a concern during the early spring when cool, cloudy conditions are common. It may be necessary to allow the water to warm slightly before adding the herbicides. Follow the setback laws with regard to the proximity of wells when handling and mixing herbicides.
Finally, consider the potential for problems to develop when a herbicide mixture is allowed to settle for long periods of time. Many products tend to settle and cake at the bottom of the spray tank. Mechanical stirring, a compatibility agent, or both may be necessary to resuspend the herbicide mixture. It is better to mix only the amount of herbicide you will apply at one time.