During this year’s 25th National No-Tillage Conference, one of the interesting hallway conversations dealt with the clash between a Purdue University weed scientist and organizations that sell or promote annual ryegrass as a cover crop.

As several no-tillers pointed out, Purdue weed scientist Bill Johnson is no fan of annual ryegrass and believes suppliers and some conservation groups oversell the weed control benefits of cover crops, especially annual ryegrass.

In a later phone conversation, Johnson told me his plot work indicates annual ryegrass is difficult to kill and that it has many of the same characteristics as weeds (dormancy and continued germination through the season, as well as a high propensity to develop herbicide resistance). He also feels it’s foolish to promote it as a cover crop when glyphosate-resistant annual ryegrass is likely already in Kentucky and other corn- and soybean-producing states.

Johnson feels annual ryegrass doesn’t help with control of summer annuals that emerge after a cover crop is terminated in the spring. However, he does recognize it works better with some winter annual weeds.

Annual ryegrass is definitely popular as this year’s No-Till Farmer benchmark study (pg. 42) found 28% of growers seeded it as a cover crop in 2016.

Tough on Annual Ryegrass

What really upset no-tillers was a 4-page report on “Cover Crop Do’s and Don’ts” that Purdue issued last summer. Co-authored by Johnson, the report’s weed management section contained the following statement:

“Don’t use annual ryegrass as a cover crop. Purdue Weed Science does not…