The use of seed blends for annual ryegrass cover cropping may not be the best idea. Here’s why:
Each variety of annual ryegrass has certain characteristics for growth, including how quickly it comes out of dormancy in the spring. And there’s a potential problem with that: if you spray the annual ryegrass with glyphosate when the grass is still dormant, none of the herbicide will be absorbed by the dormant plants. Thus, while the application may kill the actively-growing annual ryegrass varieties, those varieties still lying dormant won’t be affected.
There are a couple ways to deal with this issue. The first is to plant only one variety, one that has been tested for the Midwest and has the capability to stand up to harsher winter weather. When applying glyphosate to a single variety, there won’t be any difference in the time the entire cover crop field comes out of dormancy.
If you’re facing this spring with a field of annual ryegrass blend, you must be more vigilant about the burndown. The best bet, if weather cooperates, is to give the entire cover crop an extra 5 – 7 days to come out of dormancy. It’s a bit tricky to tell what’s an actively growing plant, so ask your crop consultant if you have doubts. But, with an extra week before burndown, you will likely be spraying plants that have all come out of dormancy.
Sometimes, after spraying annual ryegrass, it appears that the job has been done…the grass looks brown and dead. But be watchful; sometimes the kill hasn’t been complete and new growth can occur. Scout your field in the week or so after the first glyphosate application and see if it’s completely killed. If not, a second application of herbicide will be needed.
For more information about the fine points of burndown, check out the handy one-page reference on the General Information page in this blog section, for today’s date. Otherwise, you can also check out the same information on the annual ryegrass cover crop website. (News releases 2013 – Annual Ryegrass Control)