Weed science educator Brady Kappler recently summarized three years of glyphosate research conducted at the University of Nebraska. The studies looked at weed-control results from Roundup UltraMax, Roundup Ultra, Roundup WeatherMax, Roundup UltraDry, Touchdown, Clearout 41 Plus, Glyfos Xtra, Cornerstone, Glyphomax, and Glyphomax Plus. Weed-control results from these brands were remarkably similar over the course of the research.
There are, however, significant differences in how the different brands must be used. Kappler says the most important two factors are knowing whether to add surfactant and always adding ammonium sulfate (AMS) to glyphosate. The glyphosate product label will say “no surfactant is needed,” “you may add surfactant” or “you must add surfactant.” The “no” and “must” statements are easy to understand, but the “may” statement is confusing.
“May” means that your glyphosate product contains some surfactant but that this may not be enough in the right environmental situation. If you are spraying tall weeds or are in very dry conditions, adding 0.25% (1 qt./100 gal.) surfactant to the glyphosate tank may be beneficial. AMS will help combat hard water problems and improve glyphosate's efficacy. Always add at least 8.5 lbs./100 gal. or the equivalent 1% rate for liquid AMS.
Kappler notes that higher-priced brands may also come with a higher level of service from the company. As you sort through the glyphosate products, be sure to find out the surfactant load situation, plan to add AMS, and choose a product with which you are comfortable.
For the complete summary, visit cropwatch.unl.edu/archives/2004/crop04-13.htm#hail.