Some corn has shifted up into road gear, and it looks pretty good. Other corn fields are stuck in idle as the days of summer are now getting shorter.

In some years corn has reached pollination by this point, but this year much of it is less than waist high and not ready to show silks and tassels, and may still look yellow because all of the expensive nitrogen you applied last fall has disappeared. If you have more ducks and white caps in your field than corn plants, there may not be much hope; but if there is a chance to help it along, let’s see what can be done.

The 2008 corn crop throughout the Cornbelt is uneven, growth rates vary widely, and the lack of nutrients have resulted in yellowing and stunted growth, says Iowa State University agronomist John Sawyer. He has produced a pair of fact sheets on Yellow Corn, Wet Soils, and N Loss.

In the first of the series, Sawyer says the initial problems of corn resulted from wet soils, and not so much the lack of nitrogen, since N requirements are low in young corn. But he said crop rotation had a significant role in the performance of corn this year. Sawyer said corn following beans outperformed corn following corn, even when nitrogen had been applied at a 240 lb/A rate.

But what was the reason for the yellow color? Sawyer says his analysis is that nitrogen was either lost from the fall application or has moved deeper into the soil and not yet become available to the corn roots. He says there has been a more positive reaction to the spring application, but only time will tell about the impact of the heavy rains on total nitrogen available for the corn.

What can be done now? Sidedress, says Sawyer, and inject it to root depth, not put it on top of the soil hoping for rain. He says the corn needs the nitrogen more than the moisture. He adds that corn will soon be in its rapid growth phase and will need the nitrogen.

In the second fact sheet of the series, Sawyer says corn on higher ground will respond to the nitrogen quicker than corn on low ground, where wet soils suppressed the response. But after the soils drain, all of the corn will show a positive response, however the response it better to the spring applied nitrogen, even at the lower rates of application.

Sawyer’s research was directed at depth of nitrogen injection, and he found that in low areas, the corn responded better to the more shallow depth of injection and on the higher ground the corn responded better to the deeper injection.

• Purdue’s fact sheet on estimating nitrogen loss
• Illinois’ fact sheet on deciding whether to apply more nitrogen

Summary:

If you are trying to grow corn, and it does not want to cooperate this year, nitrogen may be one of the barricades to success. Fall applied nitrogen may have been lost or corn roots may not have found it yet. Spring nitrogen, applied in the root zone, may get a good response. The nitrogen issue is also complicated by whether corn followed corn or soybeans.

Stu Ellis