Herbicide manufacturers expend considerable effort to determine what adjuvants provide the most consistent product performance. Sometimes labels give users options on what adjuvant to use with respect to environmental conditions, target species, and tank-mix partners. For example, hot, dry weather hardens plants off and reduces herbicide absorption. Under these conditions the higher rates of a COC or surfactant would be beneficial. A surfactant might be more appropriate than a COC under these conditions in order to reduce the risk of crop injury.
Ammonium based fertilizers are especially important for many herbicides when velvetleaf is present.
Also be sure to consider the impact of the spray additive on tank-mix partners. The use of spray additives for one product may not be appropriate for another product. Finally, in recent years several products have been introduced that contain more than one type of additive. Before using combination products determine the components and the rates of each component to ensure that they are appropriate for the intended use. Proper use of spray adjuvants is a critical step in successful postemergence weed control.