With tighter economic conditions, there has been increased interest in using legume cover crops to supply nitrogen to corn, a Penn State University fertility specialist says.

Doug Beegle says a recent summary of available research has shown that red clover established in wheat or oats and then left to grow as a cover crop until the next season can contribute between 45 and 155 pounds of nitrogen per acre to the next corn crop.

"We can probably reliably count on 80 to 100 pounds of fertilizer-equivalent nitrogen from a good stand of red clover cover before corn," Beegle says of the research he's reviewed. "The stand and growth definitely makes a difference in the amount of nitrogen available. Adjust these credits down for poor stands or poor growth before termination.

"For an investment of around $25 per acre for seed and planting, we can get around $40 worth of nitrogen, plus the non-nitrogen yield benefits from the red clover cover crop."

Following is a summary of some of the research that Beegle has reviewed:

  • Research several years ago in northeastern Pennsylvania showed that 80 to 144 pounds of nitrogen was received from red clover established in wheat or oats.
  • More recent research in central Pennsylvania found 62 to 110 pounds of nitrogen per acre from red clover established in wheat.
  • A similar experiment at Landisville, Pa., in 2008 found the nitrogen contribution from red clover was only 40 pounds per acre. However, at this location, the corn following the clover cover crop actually required more nitrogen to achieve the maximum economic yield than the corn with no cover crop. Interestingly, this was because the maximum yield following the red clover cover crop here was 30 bushels per acre higher than the maximum yield with no clover.
  • In 2007 at Centre County, Pa., the yield following the clover cover crop was 17 bushels per acre higher than with no cover crop. This represents a  significant non-nitrogen contribution from the cover crop, which further increases the value of the cover crop.

Beegle says some farmers are also harvesting one cutting of hay from a clover cover crop, which adds an additional value. However, he says the nitrogen contribution will be reduced around 30 pounds per acre if the hay is harvested.