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As mentioned in the forage article, cereal rye is an excellent cover crop that can be seeded this fall and used as winter and early spring pasture. The rye needs to be killed two to three weeks before planting corn to reduce the potential for seedling damage from the decaying rye residue. This is easily done with an application of a glyphosate herbicide; however, there has been some confusion about rye being glyphosate-resistant. Cereal rye is not, but some species of ryegrass are.
Several speakers at various no-till educational events have warned against using ryegrass as a cover crop because of concerns about glyphosate resistance. Annual and/or perennial ryegrass is getting to be one of the more popular cover crops for no-tillers further east in areas of greater rainfall. They report that the roots go down about 3 to 5 feet, depending on the growing conditions, even though the top growth is only about 6 to 8 inches. It's planted in September or early October and sprayed out in April before it joints. After it joints, it's almost impossible to kill. There is glyphosate-resistant ryegrass in Missouri and in Australia.
If using ryegrass as a cover crop, be careful about species selection. Australian and Italian ryegrasses may be glyphosate-resistant. The Oregon Ryegrass Association claims that the seed provided by their members is not, as seed production fields are never sprayed with glyphosate so resistance shouldn't develop. So far, Gulf ryegrass and several other species are not resistant. If ryegrass is sprayed with glyphosate and doesn't die, make sure it doesn't go to seed, producing resistant seed. Several other herbicides are available to kill ryegrass but resistance may be developing to some of these as well, if multiple generations of the same seed stock are used as resistance develops over time.
When a cover crop is seeded into corn residue, the corn residue under the growing cover crop decomposes rapidly because of the additional biological activity and the increased humidity under the canopy. The corn residue and the subsequent cover crop residue after it's killed decomposes, building soil and releasing tied up nutrients. Cover crops on soybean residue add more residue to help protect the soil surface and add more carbon biomass to the system. On soils with excess water, the cover crops can be used to help dry the soil while providing roots and biomass to help build the soil. In areas where soil moisture may be short, the cover crops need to be killed earlier to conserve water but still provide cover and soil structure improvements that may be needed.
If considering rye as a cover crop, use cereal rye (the grain) as it's a good forage and it is easy to control. Ryegrass may produce a more vigorous root system to help build soil structure and relieve compaction, but it may be difficult to kill. Several other carbon (grasses) and nitrogen (legumes) cover crops are available and also may be used, depending on the needs of the producer.
Paul Jasa
Extension Engineer
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