Which term refers to a mixture or formulation that enhances herbicide application?

The term that refers to a mixture or formulation enhancing herbicide application is "adjuvant." Adjuvants are substances added to herbicide formulations to improve the effectiveness of the active ingredients. They can aid in various ways, such as increasing spray coverage, maximizing the absorption of the herbicide by plants, preventing drift, or helping the herbicide to stick to the target area.

For instance, surfactants, which are a type of adjuvant, reduce the surface tension of the liquid, allowing the spray to spread more evenly over plant surfaces. Other types of adjuvants might modify the pH of the solution or help in the formulation's stability. By including adjuvants, the overall efficacy of herbicides is enhanced, leading to better management of unwanted vegetation.

While the other options mention specific types of agents related to herbicide formulations, they do not encompass the broader category that "adjuvant" represents. Buffering agents specifically adjust the pH of the application solution, stabilizers help keep the formulation effective over time, and activators might boost the action of the herbicide but fall under a more specific function within the category of adjuvants.