In a year like this with tight margins, why would you spend money on herbicide and throw a sizable percentage of it away? You wouldn’t, right? Unless you are checking water hardness in the water you use for spray solution you may be doing just that, and not even know it, says Fred Whitford, Purdue University director of Pesticide Programs.
“Minerals in hard water can tie up active ingredients of some herbicides,” he says. “Basically you’re diluting the rate of herbicide because there is less left to work on weeds.”
Here are five steps to make sure hardness of spray water won’t be the cause of poor weed control on your farm this year.
Step one. Test for hardness!
TEST YOUR WATER: Here is a simple test for water hardness. In this case the water is very hard, registering about 1,000 ppm or more.
You can do a test with a simple kit that uses litmus paper, Whitford says. These kits are available on line from various supply houses, or should be available where swimming pool accessories are sold. You shouldn’t have to spend more than 30 or 40 cents per sample for a test strip.
“You won’t know for sure if your water is hard if you don’t test it,” Whitford says.
Step two. Choose a product to reduce hardness of water
Your choice is usually ammonium sulfate or various liquid products sold to condition hard water. Research by Bryan Young, Purdue University weed control specialist indicates that if your water has 400 or 500 parts per million of minerals that make it hard, ammonium sulfate tends to work best. Alternatives to AMS can condition hard water, he observes, but AMS provides other benefits to the spray solution besides water conditioning.
Step three. Determine how much to apply
If you are using liquid products, read directions. If you are using dry ammonium sulfate, the rate is typically from 8.5 to 17 pounds per 100 gallons of water. “The water in much of Indiana tests around 400 ppm or higher for hardness,” Whitford says. “I would lean toward the high rate. “
Suppose you decide to apply 17 pounds per 100 gallons. For a 1,000 gallon tank of water, that’s 170 pounds, or about 3.5 bags. “The drawback is you’re carrying ammonium sulfate around, but it is effective,” he says. And it’s also relatively cheap, Whitford adds.
Step four. Add it to the spray water
Whitford says some recent research tends to indicate it doesn’t matter whether you add the conditioner first before adding herbicide, or after. “My preference is to add ammonium sulfate first because it is part of the process of conditioning water, but apparently it doesn’t really matter,” he says. “Just make sure the spray solution has time to agitate so the ammonium sulfate is thoroughly mixed with spray solution.”
Young says the most important thing is that water is being conditioned so that there aren’t any herbicide complexes with cations as droplets are drying on the leaf.
Step five. Don’t be alarmed that solution still tests hard
After you’ve added the ammonium sulfate, or liquid conditioner, and you decide to test the spray solution with your litmus paper, you may not expect what you find. “The water is still going to be hard,” Whitford says. “That doesn’t change. What changes is that the minerals in the water are now bound to the sulfate component of ammonium sulfate, not the herbicide. But the minerals are still there.”