Tag Archives: herbicide carryover

Annual Ryegrass – Best Friend of Deep Cover Crops

In Oregon’s Willamette Valley, 90 percent of the world’s seed for annual ryegrass is grown. Because the water table is so high, the roots need not go far for moisture. In the Midwest, it’s a different story, and that was the first major “AHA” of its widespread adoption as a cover crop.

Over the winter, annual ryegrass roots can reach to depths of five feet, although the first year will probably not produce that depth. But over a span of five years, the channels built from successive years of annual ryegrass use will provide new access for deeper growth the next year.

For this and other reasons, Indiana farmer Cameron Mills says annual ryegrass is the best cover crop out there. “Annual ryegrass still gets a fair amount of bad-mouthing,” he said at a recent conference in Oregon, where many of the ryegrass seed growers were in the audience. “The important thing is, you have to keep getting good information out there about annual ryegrass to balance the negative. One thing you hear is that it is hard to manage. Well, that’s not true either, but you do have to manage it carefully.”

Annual ryegrass, he continued, solves a lot of problems, such as erosion, depleted organic matter, compaction, annual weeds and soybean nematodes. But to get it to work for you, you must be flexible about when you apply the seed and when you terminate it.

And as for terminating it, you have to be very conscientious that the herbicide used to terminate it doesn’t remain in the soil very long – commonly referred to as herbicide carryover; otherwise, it could inadvertently retard the growth of the next round of cover cropping. See below, two fields planted on the same day, only a mile apart from one another. One field shows healthy growth, and the herbicides were generic Bicep II and Impact. The other field, where Halex GT was used, is almost barren of cover crop. Mills said that there’s nothing wrong with Halex GT…it’s a great herbicide, but you must pay attention that the herbicide used doesn’t carry over into next year’s cover crop season.

New Annual Ryegrass Management Guide for 2016

ARG in Quebec - November photoClick here for the new “Quick Guide” for managing Annual Ryegrass as a cover crop.

In addition to new tips for seeding, the guide also outlines an emerging problem for managing cover crops in the Midwest. Many farmers use residual herbicides in the field to control weeds like marestail and waterhemp.

The lifespan of some of these herbicides extends into the next growing season for cover crops and have been shown to have a “carryover” effect on the success of the cover crop.

In the next post, we’ll outline more details on the types of herbicides to watch out for and how to continue using cover crops, too.

Herbicide Carryover in Cover Crops – New Free Guides

In the past couple of years, there has been increasing concern about the impact of residual herbicides in the field hampering or killing cover crops, including annual ryegrass.

Mike Plumer, a pioneer in the cover crop renaissance in the Midwest, has published a handy guide to specific residual herbicides and his observation about their affect on different cover crops.

Click here for a selection of publications about the herbicide carryover issue..