Characterization of Surfactant Quality and Validation of Standard Water Conditioning Testing

Abstract

Adjuvants are products added to pesticide applications to increase pest control. There are many different types of adjuvants designed to solve certain problems. Surfactants are a major class of agricultural adjuvant used to increase the efficacy of pesticides. Many companies use physical and chemical characteristics to market surfactants. However, producers do not understand these characteristics. Field efficacy data should be used to effectively market surfactants, but is somewhat limited. The objective of the first study was to evaluate if chemical and physical characteristics of agricultural surfactants can be used to predict field performance. Chemical and physical characteristics tested included HLB, dynamic surface tension, contact angle, and absorption through isolated cuticles. When individual characteristics were used as covariates with field efficacy data, no consistent results were observed. Therefore, physical and chemical characteristics cannot be used to accurately predict field performance of surfactants. In 2011, Zollinger et al. published a paper titled “A test method for evaluating water conditioning adjuvants” as a standardized test method. While this has been an effective test method, a comparison of salt type used has never been conducted. The objective of this research was to validate the standardized test method using three artificially mixed hard water samples with calcium chloride, calcium formate, and calcium nitrate. Field trials were conducted near Hillsboro, ND in 2016 and 2017. Glyphosate and mesotrione were applied at 342 and 70 g ai ha-1, respectively. Three types of water conditioners were evaluated with glyphosate: diammonium sulfate (AMS), AMS replacement, and monocarbamide dihydrogen sulfate (AMADS). Herbicide antagonism was similar between the simulated hard water samples. Within each type of water conditioning adjuvant, antagonism was overcome similarly in all water types. The results of these studies validate the test method established by Zollinger et al. (2011).