Glyphosate has long been the foundation of weed control programs for Canadian growers. Its versatility, low cost and reliability made it one of the most used herbicides in the world. However, as farming practices change and weed populations shift, many growers are seeing the limitations of a glyphosate-only approach. Tank mixing other herbicides with glyphosate is becoming standard practice, not just for efficiency but also for resistance management and to control more weeds in one pass.
Efficiency in Field Operations
Efficiency is one of the most obvious benefits of tank mixing. Farms are often thousands of acres, and time is the most valuable commodity in the busy pre-seed and in-crop windows. A tank mix lets growers attack more than one weed issue at a time, saving on equipment use, fuel, and labour costs.
Instead of making two or three passes with different herbicides, farmers can combine them into one, provided the products are compatible. For example, adding a herbicide with glyphosate can extend control to species that glyphosate struggles with, reducing the need for follow-up sprays. This efficiency not only saves time but also provides more flexibility during periods of unpredictable weather, when spray windows are limited.
Resistance Management
Perhaps the most important reason for tank mixing, though, is resistance. Weeds are increasingly showing resistance to glyphosate in Canada and across the globe. Kochia, Canada fleabane and giant ragweed are three species which have populations resistant to glyphosate. Resistant weeds can spread easily, and can have significant impacts on yields, as well as the continued usefulness of glyphosate.
Tank mixing is one way to get more than one MOA into a single application. When a weed is exposed to more than one MOA at a time, resistance is much less likely to develop. It is particularly important in areas of the Prairies where glyphosate resistant kochia is widespread, as tank-mixing glyphosate with another effective herbicide can help control weeds and slow down the spread of resistance.
Growers could, for example, tank-mix a Group 14 or Group 2 herbicide with their glyphosate to ensure broadleaf weeds resistant to glyphosate are also controlled. Layering multiple MOAs like this is one way to help extend the useful life of tools we have, and help ensure future crop productivity.
Broadening the Spectrum of Weed Control
Glyphosate has an excellent spectrum of control on grasses and broadleaf species, but it’s not universal. Cleavers, wild buckwheat or dandelion are examples of tough weeds that may not be completely controlled with glyphosate alone and can bounce back from a single pass. Tank mixing with products that target these gaps broadens the spectrum of control on weeds.
For example, on pulses, farmers may need to control cleavers and volunteer canola, neither of which is fully controlled with glyphosate alone. Adding another herbicide that works well on these target weeds results in a tank mix with a much wider range of activity. This is especially important in rotations where weed populations can vary widely from year to year, based on the preceding crop and management system.
The wider spectrum also provides cleaner fields with less early-season competition, giving crops the best chance at maximum yield.
Economic Considerations
Tank mixing does come with an up-front cost, which is why many growers view it as an investment in their crops’ productivity. The expense of a resistant weed getting out of control can far outweigh the cost of an additional herbicide. Just a few seasons can turn a small patch of resistant weeds into multiple fields of disaster—yield loss, escalating herbicide costs and a host of management headaches.
Tank mixing can head off these expensive problems and provide consistent, reliable control. In addition, cleaner fields often eliminate the need for multiple in-season applications, which can help pay for the cost of that extra active ingredient in the tank.
Compatibility and Best Practices
Not all herbicides mix well with glyphosate, so there is some planning required to make a successful tank mix. Farmers should always check product labels for approved mixes and always follow the recommended mixing order to ensure the tank mix remains stable and effective in solution. A common rule of thumb to follow is WAMLEGS (Wettable powders, Agitate, Micro-encapsulated products, Liquid flowables, Emulsifiable concentrates, Glyphosate, Surfactants) as mixing in a different order may cause issues such as clogging or poorer performance. Other factors such as sprayer hygiene, water quality and weather conditions also contribute to optimising the performance of tank mixes. For example, hard water will tie up glyphosate and impact performance. Water can be conditioned with some additives to improve uptake. An agronomist can work with farmers to ensure they are using the right products and spraying in the right conditions.
Tank Mixing as Part of Integrated Weed Management
Tank-mixing should be considered a component in an overall integrated weed management (IWM) strategy and not a single solution to all weed problems. Inclusion of cultural, mechanical and chemical control tactics, such as crop rotation, competitive seeding rates and tillage, in a program will result in the most long-term control. Herbicides play a very important role, but they will continue to be most effective when used as a component of an overall IWM program.
Ideally, tank-mixing is a strategy that, along with other agronomic decisions, builds flexibility and control into an IWM program by broadening weed control, enhancing efficiency and improving resistance management. Because all aspects of an IWM program work in synergy to help preserve yield potential, tank-mixing should be included as part of that effort.
It is no surprise that growers are tank mixing herbicides with glyphosate for both practical and agronomic reasons. A single pass with an effective solution maximizes efficiency by saving time and money. Adding more modes of action to glyphosate provides increased flexibility in resistance management, and tank mixing increases the spectrum of weeds controlled to decrease early season competition and preserve crop yield potential.
While glyphosate remains a valuable foundation for weed management, its role is evolving. Tank mixing allows it to remain relevant and effective, ensuring it works in synergy with other crop protection products. For Canadian farmers facing larger farms, tighter spray windows, and more resistant weed populations, tank mixing isn’t just a best practice—it’s becoming a necessity.
