SYMPOSIA PAPER Published: 01 December 2011

A Test Method for Evaluating Water Conditioning Adjuvants


Glyphosate is a weak acid herbicide and can bind with antagonistic salts in the spray carrier. Diammonium sulfate (AMS) is commonly used as an adjuvant with glyphosate to enhance activity and overcome antagonistic salts. Water conditioning (WC) adjuvants are used at low rates and are used as AMS replacement adjuvants. However, an ASTM approved method for testing WC adjuvants has not been established. Appropriate research parameters were used to test the water conditioner definition. Glyphosate plus NIS and glyphosate plus AMS and nonionic surfactant (NIS) were used as standards from comparing WC adjuvants. WC were compared to NIS and AMS plus NIS to determine the potential to reduce or eliminate antagonism between glyphosate and antagonistic cations. Velvetleaf was a good indicator to show antagonism, the ability for AMS and WC adjuvants to overcome antagonism, and also show greater bioefficacy. Velvetleaf, a mixture of broadleaf species, and a mixture of grass species all showed similar response to WC adjuvants. Studies to test water conditioning adjuvants were conducted at multiple locations provided a high degree of precision.

Author Information

Zollinger, Richard, K.
Department of Plant Sciences, North Dakota State University, Fargo, ND, US
Bernards, Mark, L.
Department of Agronomy and Horticulture, Lincoln, NE, US
Peterson, Dallas, E.
Department of Agronomy, Kansas State University, Manhattan, KS, US
Young, Bryan, G.
Department of Plant, Soil, and Agricultural Systems, Southern Illinois University, Carbondale, IL, US
Dahl, Gregory, K.
Winfield Solutions LLC, St. Paul, MN, US
Gednalski, Joe, V.
Winfield Solutions LLC, St. Paul, MN, US
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Developed by Committee: E35
Pages: 138–146
DOI: 10.1520/STP153720120010
ISBN-EB: 978-0-8031-9013-9
ISBN-13: 978-0-8031-7523-5