With the recent cold weather and varying degrees of injury growers are looking for ways to help their young corn recover. One potential concern is the application of urea ammonium nitrate (UAN) and residual herbicides in a tank mix.

UAN is a combination of urea and ammonium nitrate and has an N content of 28% to 32%. Under normal growing conditions, young corn can withstand some UAN without significant long-term damage. However, when corn is recovering from cold stress, it is probably better to find an alternative method of applying UAN.

The safest application method is to knife or band the UAN between the rows, but broadcast application is possible if the total nitrogen rate is kept to around 60 lb N per acre. An exact "safe" level of nitrogen is difficult to predict since environmental and corn plant conditions at application affect crop response. As described below, the amount of UAN needed to improve herbicide performance is much less than what is needed as a nitrogen source. Early leaf burn on corn usually is not a lasting problem since the growing point is still underground and a very small amount of total leaf area is exposed (Figures 1 and 2).


Early season weed control is imperative to maximize corn yield. Due to wet soil conditions, many corn growers were not able to apply residual, pre-emergence herbicides after corn planting but before corn emerged; however, several residual herbicides labeled in corn can be applied after corn emergence (See this CropWatch article).


  1. tank mix partner and
  2. carrier options.



Several other residual herbicides (Balance Flexx, Bicep II Magnum, Keystone, Lexar, Lumax, and TripleFlex) are labeled for early postemergence application in corn where UAN is NOT recommended. Postemergence application of these herbicides with UAN as a carrier will result in corn injury.


  • Some leaf burn may occur.
  • See label for specific tank mix restrictions.
