It makes sense to think that the more inputs you add to a no-till field, the bigger the yield you should expect. But herbicides require different thinking, says Chris Boerboom.

“Herbicides are tools to make your weed management program work,” explains the University of Wisconsin weed scientist. “You don’t get more yield with herbicides. They work to protect your yields.”

For the best weed protection in no-till, the key is to understand how to use these “tools” to make weed management work.

“A big part of your success is knowing what weeds you have in the field, and how and when they are emerging,” he adds. For example, waterhemp typically emerges three weeks after planting, whereas giant foxtail usually appears a week after planting in no-tilled fields.

Need Early Application

In 1996 and 1997 no-till soybean field trials, Boerboom found weed competition didn’t begin to impact yields as long as herbicides were applied within six weeks of planting. Thus, no-tillers could expect to have 100-percent yield if sprayed within six weeks of planting.

Once this six-week window passes, other factors, such as growing conditions, impact yield, according to the researcher.

“Early emerging weeds produce the most weed seeds,” explains Boerboom. “Thus, they have the most potential to reduce crop yields. In contrast, late-emerging weeds produce relatively few weed seeds.”

For example, a single, early emerging Eastern black nightshade plant produces 800,000 seeds per plant. University of Minnesota research shows that when the first flush of weeds was controlled in soybeans…