Saturated soil conditions and flooding of corn fields may have caused nitrogen to be lost resulting in the need for rescue nitrogen treatment. This is especially a concern if the nitrogen fertilizer was applied in the fall. Well-drained soils are more likely to have lost nitrogen than fields that are poorly drained. Not all areas within the same field may exhibit signs of nitrogen deficiency. Aerial photography is one of the best ways to determine if a cornfield is suffering from nitrogen deficiency. When nitrogen is deficient, the corn plant will appear lighter in color than a corn plant with adequate nitrogen. The visual difference is readily visible using drone photography to obtain an aerial view. The lighter the green color the more deficient the nitrogen level in the crop. Nitrogen deficiency will appear in the older leaves first. Yellowing will occur at the leaf tip and along the leaf midrib while the leaf edges remain green giving it the appearance of an arrow.

Through the use of high clearance or aerial application equipment, corn will benefit from additional nitrogen up to tasselling. Research trials done at the University of Missouri by Dr. Peter Scharf, Extension professor specializing in nutrient management, found that up to 150 pounds per acre of urea can be applied to corn up to four feet tall without significant yield loss compared to nitrogen applied at planting. When the corn was less than two feet tall a benefit was seen when they added a nitrogen loss inhibiter to the urea fertilizer. Urea Ammonium Nitrate (UAN) solution can be dribbled between the rows of standing corn, but significant yield loss from leaf burn was seen when it was broadcast.

For more information, contact Valerie Tate, University of Missouri Extension Agronomy Specialist at tatev@missouri.edu or 660-895-5123. MU Extension programs are open to all.

Valerie Tate is an agronomy specialist for the University of Missouri Extension.