LEXINGTON, Ky. — With corn harvest almost all but wrapped up, farmers are now turning to winter wheat season. The one difference that could set this planting season apart from others is the amount of nitrogen (N) that might be required for a successful crop.

Excessive rains in the Bluegrass State and high corn yields this summer have left many fields with a shortage of N that might call for higher applications than normal, especially for late wheat plantings.

"There is just not any N left over in most of these fields to help out our wheat," said Chad Lee, grain crops specialist with the University of Kentucky College of Agriculture, Food and Environment.

In most years, there is ample N after corn harvest has been completed; however, this year’s abundant rains and generous yields mean little residual N remains in the soil. Wheat requires a small amount of N to produce a few tillers before freezing sets in. But too much N can cause excessive growth, which can make the crop more prone to being killed by freezing temperatures.

This year starkly contrasts with 2012 when severe drought left plenty of N in the soil, but corn yields tanked. With the extra N in the ground, what was intended for the corn lasted well into the next spring for that wheat crop.

Lee suggested farmers run a test prior to adding N. "Before you do any application, you first need to do a soil nitrate test to gauge if fertilizer N is needed this fall. Once you get your nitrate test, you’ll have a better idea of what you need.

"I probably wouldn’t recommend any more than 30 pounds per acre, as too much N would cause overgrowth and prone to winter kill," he advised.

Typical baseline nitrate values are approximately 8-10 parts per million nitrate collected to a depth of 12 inches. If a producer has equal to or below this range, then the 30-pound range would probably not cause enough growth to make the wheat susceptible to low temperatures.

As of the first week of November, 66 percent of winter wheat had been planted in the Bluegrass State, which is right on par with its five-year average.