Contacts: Catherine Dehdashti, U of M Extension, (612) 625-0237, ced@umn.edu
Andrea Johnson, Minnesota Farm Guide, (320) 289-2256, andreaj@mchsi.com

Sidedressing nitrogen produces highest corn yields

ST. PAUL, Minn. (6/2/2008) — Feeding nitrogen to corn roots, through a sidedress application, is a way farmers can improve yields. When corn is growing from knee-high to shoulder-high, the maximum rate of nitrogen uptake occurs.

From 1998 to 2006, scientists at the Southwest Research and Outreach Center in Lamberton, Minn. studied the timing of nitrogen application on yield. The studies show that sidedressing is a nitrogen management practice that has consistently produced the highest yields when various times of application are compared.

"When nitrogen is applied after emergence, sidedressing supplies the nitrogen at a time when there is maximum need," says George Rehm, University of Minnesota Extension soil scientist and professor emeritus. "The time of application and time of maximum rate of uptake are matched."

Rehm reminds growers that a foliar application is not the same as a sidedress application. "Regardless of the product used, very little nitrogen used in a foliar application enters through the leaf tissue," says Rehm. "The vast majority of the nitrogen absorbed by the corn plant must enter through the roots."

The efficiency of nitrogen is the same whether it enters the plant through the leaves or through the roots. "Products that might be used in foliar applications are not more effective than the traditional, less expensive nitrogen products," he adds.

Many corn producers broadcast 46-0-0, although 82-0-0 and 28-0-0 have an equal impact on corn yield when applied as a sidedress application. "Incorporation of sidedress nitrogen is recommend if 28-0-0 or 46-0-0 is used," Rehm says. "A light cultivation will work or timing application ahead of a quarter-inch or more of rain would really be good."

On irrigated corn, a split sidedress of nitrogen is highly effective to minimize the potential of leaching.

Do you have questions you'd like Extension soil scientist George Rehm to answer, or would you like to discuss agronomic practices or concerns? You can read his blog at any time at AgBuzz.com. AgBuzz.com is a cooperative effort of University of Minnesota Extension and Minnesota Farm Guide. George Rehm's blog and his answers to your questions are available at http://www.agbuzz.com.

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URL: http:// www.extension.umn.edu/extensionnews/2008/agbuzz060208.html This page was updated June 2, 2008 .
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