Nitrogen sidedressing corn is a balancing act
Each year we get a lot of questions regarding sidedress applications of nitrogen. Sidedress applications allow growers to maximize profits. However, each growing season has varying precipitation and different environmental conditions that can prohibit producers from applying nitrogen in-season.
For each bushel of corn removed, 1.5 pound of nitrogen is required. However, one pound of nitrogen is in the corn and half a pound is in the stover. For example, you want to grow 200 bushels of corn, you would need 300 pounds of nitrogen. Some of the nitrogen would come from a credit from previous crop and nitrogen from the soil to reduce the total amount of nitrogen needed for application.
If the corn crop were following soybeans, a 20- to 30-pound nitrogen credit would be applied. Depending on soil type and cropping history, 60 to 70 percent of your nitrogen should be applied at or before planting if you are planning on sidedressing your corn crop. This allows you to evaluate growing conditions and maximize profit.
When corn is in its early vegetative stages to V5, little nitrogen is needed. The largest portion of nitrogen uptake occurs during the V8 to VT (tasseling) development stages. Corn takes up very little nitrogen after pollination.
Thus, it is critical to apply your sidedress nitrogen application before the V8 development stage. Most research indicates that if the nitrogen application is made around the V6 stage, yield loss due to nitrogen stress is rare.
Soil injection or dribbling nitrogen between the rows is the best ways to sidedress nitrogen. This type of application can reduce volatilization of urea and protect the crop from foliar damage. If you are sidedressing with ammonia, it is critical that you watch soil conditions and make sure the knife track closes properly to avoid foliar damage from the ammonia escaping.
Applications of ammonium nitrate, SuperU and urea “over the top” can result in foliar damage. However, this damage is an aesthetic concern and rarely result in any yield loss.
For broadcast applications, UAN can be applied up to one-foot plants, ammonium nitrate up to two-foot plants, and urea or SuperU up to four-foot plants or the V8 stage. Broadcast applications of UAN or ammonium nitrate are the least desirable way of applying N due to the cosmetic burn. You can reduce this cosmetic burn by applying the dry nitrogen sources when the foliage is dry.
Sidedressing corn can help you apply nitrogen when the crop needs it most. Also, sidedressing allows you to evaluate current-growing conditions to determine yield potential and the proper amount of nitrogen needed to reach your yield potential. When it comes to sidedress applications, apply earlier than later in crop development. By waiting until later in the season, you have the risk of wet weather. Wet weather can sometimes delay timely applications of nitrogen and cause significant yield loss.
Visit your local MFA location for more information on sidedressing corn or to visit with an agronomist about sidedressing corn on your farm.
Dr. Weirich is director of agronomy for MFA Incorporated.