Analysis of adjuvant effects and their interactions with variable application parameters

Herbicide performance is influenced by many variable application parameters often beyond the control of the end-user. Adjuvants can provide an effective tool to farmers to overcome or diminish the effects of adverse application conditions. Adjuvants can exert their effect either through an overall increase in activity, masking the detrimental effects of suboptimal application conditions, or by more specific effects eliminating the adverse effects of application parameters. To optimise adjuvant selection or herbicide formulation, it is important that these effects can be separated. The classical experimental approach using a single or a few herbicide doses will often not allow experimenters to do so. In this paper we present a statistical concept based on dose-response curves that will provide researchers with a proper experimental tool for studies examining the interactions between adjuvants/formulations and variable application parameters.