Over the past few years, severe Midwest winters (deep freeze with no snow; freeze/thaw/freeze cycles, etc.) have created problems for lots of cover crops, since most are not immune to winterkill.
During a “normal” winter - one with moderate temps and snowfall - almost ANY annual ryegrass seed will germinate in the fall and be ready to rock ‘n roll again in the spring, provided you’ve had enough good fall weather to get roots well established (see the annual ryegrass site for guidelines on that). But there are varieties that poop out more easily when the winter turns ugly.
So, research and development of winter hardy annual ryegrass varieties continues, and we’ll report on those as the year progresses. Dan Towery has seeded two plots with a half dozen varieties, including some new ones that are experimental. The idea is to create a variety able to withstand tougher winters.
In a recent conversation about this with a noted forage specialist at the University of Kentucky - Garry Lacefield - he theorizes that some of the problem with winterkill may come from fields where livestock manure has been added. He said that the manure provides extra nitrogen, which is good for fall growth but the extra N causes “cell elongation” in the grass leaf. That allows leaves to retain more water, which are then more susceptible to freezing.
Dan Towery and others also suspect that when the ground thaws and freezes, it heaves, especially when there’s residue in the field - from crop stubble or manure. That heaving process, they theorize, can separate the cover crop “crown” from the root stalk, thus kill the plant.
Another thing Dan will be looking for is how much value the fall growth of annual ryegrass has on production in the following year, even when the grass is winterkilled. To assure that result, he is simulating a winterkill situation, by smothering the grass late this fall and then seeing next year how much benefit was provided by the annual ryegrass roots grown throughout the fall, before winterkill.
Tags: Annual ryegrass, annual ryegrass as a cover crop, Dan Towery, Garry Lacefield, winterkill
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