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Corn+Soybean Digest

Cover Crops Can Serve Corn Nitrogen Needs in Continuous No-Till

Cover crops incorporated into a continuous no-till field crop rotation can produce enough nitrogen (N) to complement, or in some cases, replace corn N fertilizer applications, according to long-term Ohio State University (OSU) Extension research.

Seven years of research at Ohio State University’s South Centers at Piketon have found that cover crops such as cow pea or winter pea worked into a corn/soybean/wheat rotation can produce enough N to support at least 150 bu. of corn/acre.

The findings indicate farmers can save money on spring nitrogen fertilizer applications while reaping the environmental benefits of cover crops.

“Cover crops produce enough nitrogen to where farmers many not need to add N fertilizer to their corn crop, but if they want to be sure of maximizing their yields, farmers can supplement the cover crops with 25-30 lbs. of N fertilizer,” says Rafiq Islam, an OSU Extension soil scientist. “That’s more than enough a farmer needs to support the corn crop.”

Islam, who also holds a research appointment with the Ohio Agricultural Research and Development Center, says that practicing continuous no-till is a challenge for many Ohio farmers because of the hits they take in yields, soil compaction, weeds and other environmental difficulties.

“No-till farmers face yield reductions right off the bat – 20-25% – and those yield reductions last a good four or five years until the soil adjusts to the new production system,” says Islam. “Also, they face compaction issues, weed control problems, wet fields and the immobilization of N because of the increased carbon being stored in the surface soil.”

Throw cover crops into the production mix and the time it takes to recover from yield losses is cut in half, says Islam.

In addition, cover crops help alleviate environmental problems. For example, including a few pounds of oilseed radish with legumes can substantially improve the benefits of cover crops.

“The roots of oil seed radish can reach deep into the soil – as much as 30 in. – breaking up compacted soils (natural strip tillage), supporting microbial diversity, facilitating drainage and improving soil structure,” says Islam “If you grow a legume cover crop along with oil seed radish, you don’t need to subsoil or deep plow. The crops work together as a natural biological plow.”

In addition, oil seed radish stores massive amounts of reactive N and phosphorus, preventing any of it from leaching out of the soil or surface runoff and making it available to corn when it needs it.

“We also found that because oil seed radish does such a good job of improving the soil quality, it forces associated cover crops (legumes) to fix more N of their own, making even more of the natural fertilizer available,” says Islam. “It’s a mutually beneficial relationship.”

Not only do cover crops serve an environmental purpose, but they serve an economic purpose as well.

“In the 1980s, the U.S. imported 24% of N fertilizer. Today we import over 60%,” says Islam. “Cover crops are an ideal alternative to that market situation. We have to think in terms of fossil fuel dependency and food security issues.”

Islam offers one cover crop rotation scenario that research has shown works: In a corn/soybean/wheat rotation, harvest corn in the fall, plant cereal rye over the winter and roll over in May in preparation for soybean planting. Cereal rye helps control weeds. After soybean harvest grow wheat, then plant another cover crop following wheat such as winter pea or cow pea. Combine that cover crop with oil seed radish to increase nitrogen production needed for next year’s corn crop. Winterkill the cover crops and plant corn the following spring.

Islam says that despite the benefits of cover crops, there are still some challenges growers face in incorporating them into their no-till system. A few include finding available seed, crucial timing of planting cover crops following wheat, planning ahead for planting cover crops, and knowing the right cover crops combination.

“Farmers need more information and OSU Extension is working to provide them with that research data in order for them to get the most of out their farm both environmentally and economically using cover crops,” says Islam.

OSU Extension is releasing a series of cover crop fact sheets throughout 2010, as well as providing production information during workshops and field days. A plethora of cover crops fact sheets are available on OSU Extension’s Ohioline at Search for “cover crops.” Look for more information at the Midwest Cover Crops Council web site at

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