What are nitrogen application options for corn?
If attempts to get N applied preplant or early sidedress have failed, or there are concerns about N supply from early fertilizer or manure applications, then mid-to-late vegetative stage application can be a helpful rescue. Having some non-N limiting(approximately 50 percent more than normal rate) reference strips or areas in the field are helpful for comparisons. These areas can be used to visually determine if corn would respond to additional N, or as a check to see if earlier N applications or carryover N is not sufficient.
These reference areas are also needed for N stress sensing tools (such as chlorophyll meters or active canopy sensors) to help guide application rates. These reference areas should be planned and N applied early in the season, or be field areas that are known to be non-N deficient. Plant and canopy sensing can begin when corn is at approximately the V8-V10 growth stage. If late N application is needed, it should be applied as quickly as possible, and not later than the tassel stage.