Soybean School: Glyphosate strategies for 2022

University of Guelph weed scientist Dr. Peter Sikkema.

Glyphosate supply has been a hot topic this winter as growers look for ways to navigate through short supplies of this critical weed control tool.

On this episode of RealAgriculture’s Soybean School, University of Guelph weed scientist Dr. Peter Sikkema joins Bernard Tobin to discuss best practices and strategies to help growers make the most of the glyphosate they have available this year.

Like any herbicide, glyphosate has its strengths and weaknesses. It is more effective on grass species as compared to annual broadleafs. As a result, Sikkema notes that growers can use lower rates on grasses, with the highest rates being required for perennial broadleaf weeds like common ragweed.

When it comes to overall strategy, Sikkema has some tips for growers who may have limited supply. “I would be really tempted to use that glyphosate in my pre-plant burndown application, simply because there aren’t any other herbicides that are as efficacious, and as broad spectrum, as glyphosate in terms of your pre-plant burndown,” he says.

“If you are growing corn and or soybean, I would really recommend in 2022 that farmers put down their best soil-applied herbicide — a program that has activity on both grass as well as broadleaf weeds.” He also notes that the program has to match the weed spectrum in each individual field on the farm. “If you get an activating rain, with some of those soil-applied herbicides, you could be clean through till harvest.”

Of course, growers will need to scout throughout the season and watch for escapes and come back with a post-emergent herbicide. “If glyphosate is available, you can use it. Alternatively, there are quite a few effective post-emerge herbicides available for corn and soybean that you could use to address those weed escapes,” Sikkema adds.  (Story continues after the video.)

Sikkema notes that spraying weeds when they are small is also essential for effective use of the herbicide. “Glyphosate is just like any other post-emerge herbicide,” he says. “You get the best activity when you apply the herbicide when weeds are relatively small.”

The time of day when the glyphosate is applied is also key for optimum performance. Sikkema’s research shows that the herbicide is most effective when applied during the “warmest, brightest, sun-lit hours of the day,” typically between 10 am and 6 pm.

Water is also an important component of glyphosate effectiveness. Sikkema advises growers to avoid hard water with high levels of calcium, magnesium and sodium and to always use clean water. In the video, he offers tips for tank-mixing glyphosate with other herbicides and foliar fertilizers and how to reduce antagonism while enhancing effectiveness. He also discusses the need to be careful when adding ammonium sulphate and adjuvants.

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