Best Options for Side Dressing Nitrogen

Yellowing corn can be a symptom of nutrient deficiency. Photo by South Dakota State University

This spring has been a logistical challenge for farmers in many ways, especially nitrogen applications. Farmers were told to forego nitrogen applications just to get the crop in and side dress later. It is now later and rain continues to fall. Nitrogen applied pre-plant in the form of UAN or Urea has the most potential for loss, primarily from leaching too deep into the soil for the late planted corn roots to catch up.

There is no clear cut method to figure out how much nitrogen you may have lost. If you applied everything pre-plant using either UAN or Urea, it may be worth the extra money to add some additional in season. The amount of rain is the driving factor to deciding how much you may have lost. Anhydrous Ammonia has less available up front in the form of nitrate and therefore will likely still be there.

There are still several good options to side dress corn with. Anhydrous Ammonia, UAN, and slow-release or sulfur coated Urea are a few. Injected or shallow incorporated with a UAN or NH3 toolbar is best. Broadcasting Urea works as well, as long as it has a urease inhibitor on it or a slow release form. If you choose to broadcast Urea, its best to do it before V6 so you are not risking yield loss. If you choose to apply all of your nitrogen this way, it’s best to get it on before the plants hit V4. Past V4, it can damage the corn plant and will cause yield loss and larger corn plants. The larger the corn plant, the more urea can end up lodged down in the whorl. As a reminder, the growing point is still below ground until around V6.

This was a good spring to have an in-furrow or starter fertilizer down with your planter. If you did not and your corn is showing some yellowing, there is still time to get some additional nitrogen applied. One important thing to remember is yield potential decreases if you planted late, so if you had a lot of nitrogen down up front you may not need to add more. Take all factors into consideration and remember the power of your organic matter to supply some nitrogen now that we are warm enough for mineralization to keep the nitrogen available to the crop.

If you have any questions, call the Latham office at 641-692-3258 and we will get you in contact with one of our experts.


Photo courtesy of