Don’t Let Cover Crops Turn Into Weeds

A weed, simply put, is “a plant out of place.” Cover crop enthusiasts are all too aware of this adage – this agronomic practice has many advantages, but at the same time winter cover crops need to be eradicated before spring planting. Otherwise, this asset quickly becomes a burden.

This year’s wet spring weather in many parts of the Midwest may present a challenge for farmers with cover crops, says Kevin Bradley, University of Missouri Extension weed specialist.

“Last year, by the first of April, we’d made our first applications,” he says. “We’re at least two weeks late this year. We can’t give a date on when to spray – weather changes everything. And the winter was a lot rougher on cover crops this year.”

While 93% is enough for an A in the classroom, that level of control is a failure in the field, he says. Enough weeds remain to steal sunshine, fertilizer and water. According to Bradley’s research, annual ryegrass, wheat and crimson clover are the toughest cover crops to kill, while cereal rye, hairy vetch and winter peas are relatively easier. Oats and radishes are the easiest – in fact, Bradley says no control was needed in central Missouri this year due to winterkill.

For this reason, Dave Robison, agronomist with Legacy Seeds, suggests farmers trying cover crops for the first time begin with a few acres of oats and radishes to gain familiarity with the practice before advancing to other cover crop options such as annual ryegrass.

“Don’t get me wrong, annual ryegrass is a fabulous cover crop with tremendous value as a cover crop and forage,” Robison says. “But, it does take more management than many other cover crops. Annual ryegrass provides high reward with some additional risk.”

Bradley offers up the following tips to maximize cover crop kill:

  • Adjust spray settings for more gallons per acre to get better coverage.
  • Spray during daylight hours when ryegrass is actively growing.
  • Spray when temperatures are 60°F or higher. Avoid spraying when day or night temperatures are forecasted to fall into the 30s.
  • Spray at least four hours before sunset for better herbicide translocation.

Here are additional control recommendations specifically for ryegrass, from the Oregon Ryegrass Growers Seed Commission.

Source: Ben Potter, Farm Journal


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