Alberta Wheat and Alberta Barley along with their Prairie counterparts have put out a five-page guide titled “Strategies for managing herbicide shortages.” (link below)
It covers management practices (such as higher seeding rates and spraying when weeds are small) but also tank mixes. While going below product rates on the label is not recommended, there may be options such as use of a non-ionic surfactant (which can increase absorption).
There is also information on different herbicide groups that could be considered if glyphosate is in short supply and links to provincial crop protection guides (including the Blue Book, which can be downloaded for free).
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To find the managing herbicide shortages document, go to albertawheatbarley.com.