Are you having issues with herbicides that previously worked for you? Herbicide resistance is an ongoing issue, and one crucial ingredient of an effective, integrated pest management strategy could be the culprit – the quality of your water. The water you use to mix with your herbicides can affect how well they work. Trent Pawlick, Regional Account Manager at our Viking, AB location, shared what aspects of water quality farmers should look out for to get the most out of their herbicides.

Not all water is created equal

Farmers have a variety of water sources, and the quality of that water could pose an issue when spraying herbicides. Most water farmers use comes form dugouts, county-provided filling stations, or a home setup with well water. All of these options likely have a high to neutral pH and most (but not all) have a high mineral content, which can cause water hardness. If not filtered properly, sloughs and dugouts can be high in sediments or aquatic matter.

Know your water’s pH levels

Having acidic or alkaline water can affect the efficacy of certain herbicides. Low pH water (6 or below) can severely affect group 2 products, or sulfonylureas, as well as group 14 by as much as 60%. These products tend to break down much quicker in acidic water, making for a weak tank mixture from the start.

Alkaline water affects the solubility of group 1 graminicides, which are used on grassy weeds. High pH also makes group 4, 6, 9, and 10 herbicides less soluble. Therefore, they are also made to be much less effective on target water species.

Water hardness and herbicides

Hard water contains minerals with positive cations such as calcium, iron, magnesium, manganese, aluminum, and zinc. These positively-charged minerals act as a magnet to the negatively charged anions in herbicides. As a result, the tank mix is more easily precipitated, which means plants have difficulty absorbing the herbicide before it evaporates.

Glyphosate is the most common product negatively affected by hard water. Group 1, some group 2, and groups 4, 9, 14, and 22 (diquat) herbicides – the latter being a desiccant and therefore an important one to consider before harvest – are also affected. Group 27 with glyphosate has been most commonly studied for its performance with hard water.

What’s hiding in turbid water?

Turbid water is what that has cloudiness or haziness to it and is caused by an overabundance of particles that are usually invisible to the naked eye.

While sprayer water doesn’t need to be potable, cleanliness is still important for tank mixing and the turbidity can affect herbicide efficacy. Studies have been done on how turbidity affects groups 1, 2, 9, and 22 chemistries because the particles in turbid water can combine with herbicides and make them insoluble.

Turbid water can also have sediments like silt, sand, and clay, as well as aquatic life that could plug the sprayer filters and nozzles.

Consider water temperature

Water temperature can also affect how well herbicides work. Water below 10°C can greatly affect weak-acid herbicides usually found in groups 1, 2, 4, 9, 10, 14, and 22 (diquat). Water that’s too warm – above 30°C or 35°C (and especially anything over 45°C) – can also be an issue =, although this isn’t usually an issue when the water is coming out of the ground.

Water temperature is probably the hardest factor to manage because of the high volume of water being used and the risk of water not being able to reach the optimum temperature. Studies have typically used water around 18°C, which seems to be the optimum temperature for herbicides to work their best. If it’s possible for your operation, consider installing black poly water tanks. Water stored in these tanks can be brought up to the ideal temperature, as they absorb heat from the sun and are protected against algae growth.

Taking steps to better water

The best thing for farmers to do to understand their water quality is to get it tested. A water quality test is very inexpensive in comparison to the cost of your herbicides becoming ineffective. A&L Canada Laboratories conducts agricultural testing, including on water, for farms across the country. You can get a water testing kit from your local P&H, and we can send your water sample away for testing. Results usually come back within 3-5 days.

If you pull water from a well, we recommend testing annually. Water tables rise and fall through the year, going through different layers of minerals in the soil, which can change the mineral content. Well and dugout water are around the neutral pH 7 or higher range. If your results show that your water is acidic, it may indicate issues around your water source.

Water testing can be done at any point in the season. As we head into the fall and prepare to apply desiccants, water testing can also help ensure that your group 22 application will work its best. Getting your water tested as early in the season as possible can help address any problems that may arise. This is especially important, as most herbicide management plans are likely to have been solidified already. Testing can help you get ahead of any potential issues your water may have with the chemistries you’ll be using.

Once your test results come back, your local P&H can also recommend water conditioners to improve your water quality. Utility modifier adjuvants, surfactants, and pH adjusters are just a few of the products that can help solve your water issues.

Consider testing your water before you head out this fall and see the difference the right water can do for your farm.

Address your water with P&H

With the right treatment and conditioning, you can make all water equal.

P&H is your partner in ensuring that your crops and your herbicide investment are protected. Find your local P&H to get started on improving your water quality today.