Nitrogen losses occur in wet soils by leaching and/or denitrification. Warm soil temperatures in June are conducive for denitrification losses in which soil microbes convert nitrate nitrogen to gas which returns it into the atmosphere. Warm soil temperatures speed the process. Leaching nitrates may be deeper into the soil profile, and unless sandy, corn roots may reach nitrate nitrogen.

Corn color is the most reliable indicator if additional nitrogen is needed. Supplemental nitrogen may be applied from side-dress through R-1. Small corn plants may be pale green in color. Larger plants may be pale in color and lower leaves have an inverted “V-shaped” yellow shape pointing in the direction from the leaf tip inward. Nitrogen deficiency will occur on the lower leaves as the plant will translocate nitrogen from base of plant upward to where it is needed.

When applying nitrogen to tall corn, care should be considered regarding the product to use.  Urea will pose less burn than ammonia nitrate so urea would be the preferred source.  Corn greater than three feet tall will not benefit from using urea plus Agrotain according to MU research. If you are using nitrogen solution, apply the nitrogen using hoses and let them drag through the field.  Splashing of nitrogen will burn corn leaves.

Ground rigs can apply high rates of nitrogen when nitrogen losses are great. Aerial applications typically apply 30 to 50 pounds of nitrogen to maintain high corn yield potentials.

Nitrogen applications applied to late season corn as rescue treatments can return cost of additional fertilizer in yield.  Care should be taken to evaluate health of corn and determine if high yield potential exists. Sometimes, if soils remain saturated for weeks, yield potential can be damaged.

For more information, contact Wayne Flanary at 816-279-1691, Field Specialist in Agronomy, University of Missouri Extension.