Higher nitrogen rates don't always equal higher corn yields in the South

Many growers automatically equate higher nitrogen rates with higher corn yields, but that’s not necessarily the case.

“Corn is very responsive to nitrogen, but high nitrogen rates may not always be the most profitable thing to look at for your program,” says Erick Larson, Mississippi State University Extension small grains agronomist.The response to nitrogen will vary from year to year, especially in a Southern environment, he adds. “There are several unique things about the environment in the South that can make managing nitrogen very difficult. It’s certainly different from what growers in the Corn Belt of the Midwest deal with,” he says.

The traditional thinking is that growers who are making exceptional corn yields are using very high nitrogen rates, says Larson.

“But a grower I know in southwest Kansas still applies only about 225 pounds of nitrogen over the course of a season and makes up to 300 bushels per acre. A definite advantage they have is their unique environment, but they’re also doing some things to increase their nitrogen efficiency. They’re producing more than a bushel in yield with each added pound of nitrogen,” he says.

Nitrogen loss in the South is associated with conditions such as excessive moisture in the spring, says Larson.

“From the day we put corn seed in the ground until it reaches physiological maturity at the end of the season and is no longer using nitrogen may be as much as 140 days or more. We’ve got a long season to work with on corn. If we have dry conditions – a season when we don’t have 35 to 40 inches of rainfall – we can do just about whatever we want without seeing a response to nitrogen