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Corn+Soybean Digest

Take Cover

Corn roots 75-in. deep. Soybean roots 38-in. plus. Believe it!

By using a ryegrass cover crop in a no-till system, Illinois researchers can boast yields that have spiked at 230 bu. for corn and an equally impressive 65 bu. for beans.

And it's not just from one-year wonder plots.

Mike Plumer, a University of Illinois Extension educator out of Carbondale, has a six-year stack of data and grower results that shows the ryegrass cover crop system can boost yields when non-cover crop production suffers due to drought.

“A ryegrass cover crop that includes good certified ryegrass seed can certainly enhance corn and soybean production,” says Plumer, who works with growers who have adopted the cover crop system.

His studies since the late-1990s illustrate how a ryegrass cover crop reduces soil erosion in winter, holds winter moisture long past planting time and opens up a deep root system. All these traits help corn and soybean roots dig deep into the soil in search of water and nutrients.

Cover crops have probably been more popular in some southern growing areas where cotton producers need protection against severe wind damage and subsequent soil erosion.

Those systems have mostly involved wheat or rye cover crops of the cereal brand. Planted in the fall after the previous year's harvest, the cover crops help hold residue and moisture during the winter, before protecting young plants from damage caused by high winds and stinging blowing soil.

Cereal rye or wheat can also help with corn and soybeans in the Midwest. But certified annual ryegrass seed, available mostly from Oregon, works best, says Plumer.

“We consistently get a 50% or better root system when compared to cereal rye, wheat or oats,” he says. “We get enough changes in the soil profile that corn and soybeans also increase rooting depth.”

The ryegrass cover crop is normally planted in September or early October, just after soybean or corn harvest. It is usually drilled or broadcast planted in. “Planting rates will vary,” says Plumer. “We are still adjusting the rates, but typically drilled ryegrass seed is planted at a rate of 15-20 lb./acre. If it's broadcast, the rate is 18-20 lb./acre. Late-season broadcast is usually 20-25 lb./acre.”

Some lower planting rates also look good. “We drilled in 12 lb./acre in one field about mid-September and it looked great (in mid-October),” says Plumer.

The ryegrass grows through the winter and early spring, capturing and conserving snow and other moisture. The cover crop is terminated about the first week of April, when the ryegrass is 6-8 in. tall.

A number of herbicides, like Roundup, Touchdown and other glyphosates and Gramoxone and other residuals are used to terminate or kill the cover crop. If the soybeans or corn are Roundup Ready, then glyphosate is a typical burndown herbicide and can be used to follow up on escapes. Farmers should count on two herbicide applications for best control.

After six years of continuous cover crop studies, Plumer says corn roots are going as deep as 75 in. “Corn crops on the six-year land yielded about 180 bu. this year,” he says, adding that non-cover crop fields in the same region yield 130-140 bu. “Yields were in the 150-180 bu. range for fields under the cover crop system for a short time.”

Soybean roots in the cover-crop system are 38-42 in. deep after six years and 30-32 in. after short-term cover crop growth.

Yields are not quite as dramatic as those for corn, but still outshine regular no-till production. “Our soybean yields are 55-65 bu. and are consistently 5-8 bu. higher than where there is no cover crop,” says Plumer.

There are some negatives with using cover crops, as with nearly any cropping system. A good cover crop program requires more attention to management, especially during the herbicide burndown period, he says.

“You don't want the ryegrass to become an unwanted weed in the growing season,” he says. “That's why it is essential that it's all controlled.”

Termination and cleanup can cost $15-20/acre if it is not controlled with the first application. That's on top of ryegrass seed cost of $6-12/acre. Beware of bad non-certified seeds. Plumer says some growers have seen problems from glyphosate-tolerant ryegrass seed, or “rigid ryegrass.” There are concerns about rigid ryegrass contamination or herbicide resistance, so certified seed is a must in this program, he says.

For more information on certified ryegrass seed, go to

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