By JEFF BURBINK
Extension Educator, Purdue Extension Elkhart County

GOSHEN — It’s that time of the year. Many farmers, nursery owners and homeowners will soon be spraying fields and yards with burndown products to reduce early season weed pressure before planting.

One of the more popular herbicides for burndown is glyphosate, which is the active ingredient in Roundup and many other products.

Glyphosate kills plants by binding to an enzyme called EPSP synthase. When bound to EPSP synthase, the enzyme cannot function and the plant cannot produce three critical amino acids. Plant begins to starve to death soon thereafter.

If you have used glyphosate before, you know that it must come in contact with green, growing tissue to work properly. Glyphosate that falls onto the soil is rapidly and tightly bonded to the soil and organic matter. It has no effect on weeds at that point. In fact, using turbid (dirty) water, or hard water will greatly reduce herbicidal activity too.

Hard water also affects glyphosate’s performance. Calcium, magnesium, iron or sodium can form a complex with the glyphosate molecule so that it is unable to bind to EPSP synthase. If glyphosate cannot bind to the enzyme, it will not provide control.

Much of the groundwater in Elkhart County is naturally hard water, so it comes as no surprise that most farmers have learned to deal with this. Adding ammonium sulfate to the spray tank before adding the herbicide can overcome adverse effects of hard water.

The amount of AMS to add to water can range wildly from 4.25 to 17 pounds per 100 gallons of water. Just check the label of your herbicide for the details. Fortunately, AMS is a pretty cheap fix. All you really need is a hard water test, available at most water softener companies and you will have the information you need to decide how much AMS to add.

Glyphosate is not the only herbicide that benefits from this additive. Picloram, glufosinate, dicamba, clopyralid, bentazon, acifluorfen and 2,4-D and among a few of the other products that are enhanced by AMS when blended with water before the herbicide is added.