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Corn+Soybean Digest

Rain-Soaked Cornfields May Need Nitrogen

COLUMBIA, Mo. -- Farmer pessimism over low corn prices may prevent profiting from a proven practice, fears Peter Scharf.

The University of Missouri soil specialist urges corn producers to scout their fields for nitrogen loss after recent rains. Nitrogen applied where fertilizer has been lost can boost yields.

"Heavy rains since May 1 have created the potential for nitrogen loss," Scharf said. "Nitrogen applied in April may have leached out of the Corn root zone."

MU field tests in the 1990s showed that nitrogen-stressed corn could respond well to late nitrogen fertilizer applications.

"We saw a yield response of over 100 bushels per acre once, when the corn was head high," Scharf said. "Even at silking, yield response can still be large. Yield increases of at least 35 bushels per acre were obtained all three times we tried it."

MU extension specialists Bill Wiebold, John Lory and Scharf conducted the studies.

Sandy soils are most vulnerable to nitrogen leaching, Scharf said. "Nitrogen moves down with the water, typically at the rate of 6 inches for every inch of rainfall." Poorly drained soils may also lose nitrogen. "When soils are saturated or nearly saturated they are low in oxygen. In that condition, nitrogen is converted into an unusable form. Eventually, it is lost to the air," Scharf said.

Field scouting is a critical element to determining corn that needs treatment. "Roadside looks, or standing on the edge of the field, will find some, but nitrogen deficiencies may be missed in the middle of the fields," he said.

Scharf urges farmers to walk through fields about four or five days after fields become walkable. "Scouting will be most accurate and useful then," Scharf said.

All corn tends to look yellow after days of standing in cool, wet soil without sunshine. A couple of days of sunshine will take care of that. "If the nitrogen has not been lost, it will take that long for corn to grow out of it," he said.

Rescue treatments can be applied with good results up until the corn is

silking, or is head high, Scharf said. "Scouting for evidence of nitrogen loss and then responding with nitrogen applications when appropriate could be profitable for producers this year."

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