Corn growers who apply sidedress nitrogen (N) fertilizer early can increase their chances of getting maximum benefit. There’s no benefit to delaying the application until a later plant growth stage, says University of Minnesota extension soil scientist George Rehm.
Rehm says that, in a University of Nebraska study, researchers established different N-deficient levels early in the growing season by applying various rates of N fertilizer immediately after planting. They then applied additional N at different times during the growing season. Total N applied was 230 lbs/acre of ammonium nitrate (33-0-0) for all treatments.
“In general, the highest yields resulted from applying some of the nitrogen at planting and the rest at the V4 growth stage,” says Rehm. “Delaying the second application to the V8 growth stage did not improve yields. It’s also important to note that high yields resulted with a single N application at the time of planting.”
Further details on the Nebraska study are on the Internet in an article entitled “In-Season Nitrogen for Corn.” Go to http://www.plpa.agri.umn.edu/extension and click on the icon for "2003 Minnesota Crop News."