The planting date of corn certainly can affect its yield potential.

Corn planted in mid-June at two University of Illinois trials last year in Southern Illinois yielded 10 to 40 percent less than corn planted in April through late May, according to Steve Ebelhar, agronomist at the U of I Dixon Springs Ag Center.

“We have a wide window to plant corn in Southern Illinois, but it’s not as wide as we hoped,” Ebelhar told FarmWeek last week at the Illinois Fertilizer and Chemical Association’s annual convention in Peoria. “If you can plant corn before the end of May, you can get pretty reasonable yields.”

Nitrogen uptake, on the other hand, is not affected as much by planting dates, based on recent research.

“The responses to N were about the same (in field trials), regardless of the planting date,” Ebelhar said. “We don’t see a need to increase N rates based on the planting date.”

The same held true for corn-on-corn, according to the research.

Yields in many areas were considerably lower last year for corn-on-corn compared to a corn/beans or corn/wheat/beans rotation, but the N rate in many cases had little to do with that outcome.

Emerson Nafziger, U of I Extension agronomist, recently said the real problem with corn yields, particularly for corn-on-corn in 2010 and 2011, was a lack of water during the critical grain-filling period.

Nitrogen typically enters corn plants in water droplets through the roots. So the amount of nitrogen available in the soil didn’t matter much last July and August when precipitation dried up or was non-existent across much of the state.

“We didn’t see a response (in corn-on-corn yields) by adding additional N,” Ebelhar said.

U of I research also found little yield response when it compared broadcast fertilizer applications vs. deep-band applications, according to Fabian Fernandez, U of I Extension assistant professor of soil fertility.

Research, however, showed a yield bump in strip-till corn vs. no-till corn.

“The data indicates there is a benefit for strip-till,” Fernandez said. “It very likely is related to water availability (in strip-till systems) and improved nutrient availability because of that water.”

U of I researchers in the future plan to study nitrogen removal rates in corn to see if the rates have changed due to hybrid advancements, Fernandez added.