Is Your Water Ruining Your Weed Control?

Small factors can quietly reduce herbicide effectiveness.

- Chelsea Dinterman

There’s a lot to think about when it comes to weed management. Which herbicide you use, when you make applications, and how many resistant weeds have infiltrated your field are just a few questions that come to mind. But when was the last time you thought about your water?

While water often makes up 95% of a spray solution, it’s often an afterthought. Even worse, water-quality-related impacts on herbicides can often be attributed to other factors. But as margins continue to tighten, a deeper look at every aspect of your herbicide program could benefit your bottom line.

“Water quality is something farmers really need to pay attention to,” said Derek Emerine, the national agronomist for Helena Agri-Enterprises. “I know margins are extremely tight right now, and the most expensive herbicide application is the second one you have to apply because the first one didn’t work.”

Water Hardness

Water hardness — the amount of calcium, magnesium, or other positively charged ions (cations) in the water — is often the primary concern.

Herbicides formulated with weak acids are most prone to hard water. This is because molecules in the herbicide can bind to cations in the water, reducing or completely neutralizing the product’s ability to stop weed development.

“Glyphosate is a great example of this, but other herbicides can be affected as well,” said Sarah Lancaster, an Extension weed specialist at Kansas State University.