If you applied 200 units of nitrogen to your corn, would you know how many units would be left at harvest? Before the season even begins?

Bryan Young asks that question because it’s the same concept with herbicide carryover — a grower can’t know how much of his herbicide will still be present later in the season before he even applies it.

The Purdue University weed scientist instead says that when it comes to herbicide carryover on cover crops, the best thing growers can do is arm themselves with information to reduce concern about carryover.

“It’s not ‘You’re free, in the clear’ over here and ‘You’re doomed for failure over there,’” he says. “It’s kind of less or more concern. That’s where we’re at right now.”

At the 2016 National No-Tillage Conference, Young shared tips to consider for creating a weed control program that won’t damage cover crops down the road. 

Environment Matters

If a grower calls Young and asks him whether his herbicide is going to carry over and hurt his cover crop, Young will ask two questions:

• Did you get any rain on it?
• What was your environment?

The environment, which includes rainfall, temperature and soil type, is what he considers to be the No. 1 factor that influences herbicide carryover because it determines how long the herbicide will last. Soil adsorption in particular is the biggest determiner of how much herbicide will be there later.

“If it’s bound to…