There is some confusion when it comes to knowing the differences between annual ryegrass and cereal rye. Many confuse these crops because they share the word “rye” in their names. Annual ryegrass is a cool-season grass, while cereal rye is a grain that has growth characteristics much like wheat. Annual ryegrass seed costs slightly less than cereal rye, is much smaller and weighs 26 pounds per bushel. The seed of cereal rye is much larger and weighs 56 pounds per bushel.
Like many cover crops, annual ryegrass builds soil, reduces runoff and erosion, sequesters nitrogen, improves water infiltration and increases organic matter. Annual ryegrass is easy to establish in the fall with adequate moisture. For best results, it needs to grow for 45 to 60 days before freezing temperatures arrive. Annual ryegrass is more susceptible to winterkill, which can be caused by a lack of snow cover combined with very low wind chill and multiple freeze-thaw events.
Annual ryegrass residue breaks down more quickly than that of cereal rye. In trials in the Midwest, about 70 to 80 pounds of nitrogen per acre were available to the following row crop, after annual ryegrass was burned down. These results depended on field history.
According to Dale Strickler, an agronomist for Green Cover Seed in Iola KS, annual ryegrass, while not a cereal grain, is a viable fall-planted grass option. “While the above-ground biomass of this species is far less than rye or triticale, the root system is massive. Annual ryegrass roots 36 inches deep have been observed from plants that are only 6 inches tall.” He adds that Diploid varieties like Winterhawk can survive winters in zones 4B and 5A (Nebraska) and south but need to be established sooner than cereal rye to have the best survival chances. “We like to see annual ryegrass established 2 weeks ahead of your first frost if possible to maximize root development prior to overwintering.”
Many farmers look for a cover crop capable of breaking through layers of soil compaction. Annual ryegrass performs much better than cereal rye, especially below 24 inches. The roots of row crops will follow the annual ryegrass roots deeper for nutrients and moisture that otherwise would not be available. Mike Plumer, a University of Illinois Extension agronomist and cover crops specialist, says he would never recommend cereal rye to solve soil compaction.
Cereal rye will survive in low rainfall, but it doesn’t do well in excessive moisture. It also grows fine in low soil fertility and sandy soil. Annual ryegrass does just fine in a wet climate. While it prefers fertile soil, annual ryegrass does well on poor, rocky soils and will do better than cereal rye in denser clay soils, according to the Sustainable Agriculture Network.
More biomass is a plus for cereal rye during the fall, winter and early spring because it provides good weed control. Annual ryegrass also is effective with weed control.
Strickler says winter cereal rye remains the undisputed king of cover crops due to its extreme cold tolerance and wide planting window. “With the ability to germinate in soils as cold as 34 degrees, it can be planted very late in the season and still successfully vernalize. It is the first crop to break dormancy in the spring so it is the best weed control of anything you can plant in the fall.” He adds that it is by far the best cover crop ahead of soybeans and it can be used ahead of corn as long as a good nitrogen management plan is in place.