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Published June 07, 2008, 12:00 AM

Will's Windmill column: Side-dressing nitrogen produces highest corn yields

Feeding nitrogen to corn roots, through a side-dress application, is a way farmers can improve yields.

By: By Will Yliniemi, DL-Online

Feeding nitrogen to corn roots, through a side-dress 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 side-dressing 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, side-dressing 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 side-dress 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 side-dress application. “Incorporation of side-dress 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 side-dress of nitrogen is highly effective to minimize the potential of leaching.

Early effects on corn influence later development

With our corn planted, it is important to remember that the first few stages of corn growth will set the tempo of the hybrids health and yield. Starting with emergence, the corn plant develops primary roots and by the second leaf stage (vegetative stage-V2) has first whorl roots elongating.

By V4, the plant has second whorl roots elongating with these nodal roots already a major part of the root system. At this same time, the growing point is still below the soil surface. However, leaf and ear shoots are already being initiated. This initiation will be complete by V5 (five-leaf stage). Also by V5, a microscopically small tassel has been initiated at the growing point.

Soil temperatures can greatly affect the corn development even with the growing point below ground. Colder soil temperatures (below 50 degrees Fahrenheit) can increase the time between leaf stages, delay tassel formation and reduce nutrient availability. The growing point, however, is protected from hail, wind or frost while under ground.

Unfortunately, the growing point is not protected from saturated soil water conditions. Remember that early weed control is also important. Weeds compete for water, nutrients and light. Chemical control, cultivation and higher plant populations or crop rotation can reduce weeds. If cultivation is used, shallow cultivation after V2 is important, as deeper cultivation will destroy nodal roots.

For more information on crop production and related topics, please contact me, Will Yliniemi, Hubbard/Becker County Extension educator, by phone at 1-218-732-3391 or 1-218-846-7328, by cell at 1-218-252-1042, or by e-mail at ylini003@umn.edu.

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