The water farmers use for mixing herbicides often comes from surface or groundwater sources, and a lot of those are pretty hard. In farming talk, water hardness just means how many of those positively charged ions, mainly calcium and magnesium, are floating around. When these ions are in your spray water, they love to bind with the negatively charged glyphosate molecules.
Once they’re stuck together, glyphosate forms these clumps that plants just can’t absorb as easily. This means less glyphosate gets into and moves throughout the plant, especially for stubborn weeds like wild oats, kochia, and Canada thistle.
Farmers might notice that weeds die more slowly, or only get partially controlled, or even start growing back when they spray with untreated hard water – even if they’re using the right amount of herbicide with glyphosate.
How Hard Water Messes with Glyphosate
Glyphosate works by getting absorbed through the leaves and moving to specific growth points in the plant, where it shuts down a key enzyme. But calcium and magnesium ions throw a wrench in this process by:
- Forming glyphosate salts: These make it harder for glyphosate to move through the plant.
- Making absorption tougher: These salts are heavier molecules, so they don’t get into the leaves as easily.
- Reducing how well it works: Once bound, glyphosate just isn’t as good at doing its job and messing with those plant enzymes.
Even moderately hard water—as little as 150 parts per million (ppm)—can make glyphosate less effective. In many parts of the Prairies, the hardness is over 300 ppm, especially where water comes from limestone or glacial sources.
Smart Solutions for Hard Water
Good news! We can totally deal with hard water by planning ahead and using effective water conditioning agents. These additives either bind up or “trap” those hard water ions, keeping glyphosate available and ready to work.
1. Ammonium Sulfate (AMS)
AMS is pretty much the gold standard – it’s super effective and affordable for conditioning glyphosate spray water. Here’s how it helps:
- Binding hard water ions: The sulfate ion (SO₄²⁻) teams up with calcium and magnesium, stopping them from messing with glyphosate.
- Boosting leaf uptake: The ammonium ion (NH₄⁺) acts like a delivery truck, helping glyphosate get into plant cells.
- Speeding up absorption: Solutions treated with AMS dry faster and are better at sticking to the plant, even if it rains.
For water with moderate hardness, the usual AMS rate is about 8.5 to 17 pounds per 100 gallons. If your water is super alkaline or extremely hard, you might need a bit more.
2. Commercial Water Conditioners
You’ll find a bunch of specialized crop protection products out there designed to tackle water hardness. These often include:
- AMS, but in a liquid form that’s easier to handle
- “Trapping” agents like citric acid
- Ingredients that balance pH and improve spreading
Some examples are LI 700®, Class Act® NG, or Choice® Weather Master. You can use these on their own or with AMS, depending on what your water test shows and what kind of glyphosate you’re using.
3. Test Your Water and Calibrate!
Before you start adding conditioners, it’s a really good idea for farmers to test their water to see how hard it is. Testing kits are cheap and simple to use. Knowing the exact level of those pesky ions lets you use just the right amount of AMS or conditioner, making your glyphosate work better and saving you money on unnecessary product.
Best Practices for Mixing and Spraying
To get the most out of your glyphosate in hard water, follow these mixing and conditioning tips:
- Condition the water first: Always add AMS or other conditioners to the tank before you add glyphosate. This stops those ions from binding with glyphosate before they can be neutralized.
- Mix in the right order: Use the WALES method—Wettable powders, Agitate, Liquid flowables, Emulsifiables, Surfactants and conditioners last. Remember, AMS goes in before any other active ingredient.
- Watch for water source changes: If you switch between well water, dugout water, or municipal water, test the hardness again.
- Clean your sprayer tanks regularly: Minerals can build up in tanks and plumbing over time, which can mess with your water quality.
Additional Considerations
While glyphosate is often used by itself for pre-seed burnoff or fall applications, it’s more and more being mixed with other products to manage resistance or get broader weed control. Many of these other products – especially Group 14 or Group 2 herbicides – also benefit from conditioned water for better mixing and stability.
Plus, as weeds in certain Prairie areas become more resistant to glyphosate, getting the best possible performance from every application isn’t just about saving money; it’s about being responsible and protecting this vital tool.
Hard water might be invisible, but its impact on how well herbicides work is huge—especially for systemic options like glyphosate. In the Prairies, where hard water is a common hurdle, not conditioning your spray water can lead to bad weed control, needing to spray again, and ultimately, losing out on productivity.
