Time to Trust Nitrogen Trials!

Turning down the dial can be traumatic, but profitable.

Published on: Feb 11, 2008

Dave Nanda is one of the few agronomists who still likes to talk about pounds of nitrogen that you should apply depending upon your yield goal. He recommends applying 0.9 pounds of commercial N following soybeans for every bushel you expect to produce. If you’re after 165 bushel corn, that works out to be about 145-150 pounds of N per acre. Nanda is president of Bird Hybrids LLC, Tiffin, Ohio, and consultant for the Farm Progress Corn Illustrated project.

Most other universities, including Iowa State University, the University of Illinois and Purdue University are shying away from pegging a pound of N per bushel of corn number. Instead, they’re taking a look at past documented trial results, and using computer programs to come up with nitrogen rates that they feel are realistic season in and season out. What no one knows, of course, is exactly what the season will be like in any one location across the Corn Belt.

Purdue University recently completed two years of updated N trials, doing some on university research farms and some on farmer’s own land. Their goal was to build a bank of data so that they could enable Indiana farmers to use their own numbers if they wanted to plug into computer programs offered by such universities as Iowa State. The program housed there was developed with a big push from agronomists at the University of Illinois.

Bob Nielsen and Jim Camberato, Purdue University corn and fertilizer specialists, respectively, have determined that the optimum agronomic rate for corn following soybeans in Indiana is about 175 pounds per acre. They acknowledge, however, that it varies from one side of the state to the other, and from year to year. The optimum economic rate, however, for total commercial N applied after soybeans is around 147 pounds per acre.

Ironically, Nanda and Purdue arrived at almost exactly the same spot for reaching maximum economic yield, that’s the most profitable rate of application, not necessarily the highest yield possible to obtain. With n at nearly 50 cents per pound for anhydrous ammonia this spring and considerably higher for other forms of nitrogen available on the market, the term ‘economic optimum’ suddenly takes on a new importance and meaning.

Nanda consults with various farmers. He recently convinced one farmer who routinely applied 165-175 pounds of total extra N per acre after soybeans to drop back to 145 pounds per acre. If the farmer had any hesitation, it vanished when N moved toward 50 cents per pound. That means a 30-pound drop in rate is worth $10 per acre, or $10,000 on 1,000 acres.