Ammonia Damage to Corn

There is potential for ammonia damage to corn especially in dry springs. The risk will vary with the soil moisture, soil texture, depth of the ammonia placement, and rate injected into the soil, and proximity of the corn seed to the ammonia band.

Ammonia burn can be diagnosed by locating the knife track and where the seed was planted into this track. The damaged roots will be brown and look as if they were burned. They will not grow into the ammonia zone until later. The corn plants may also take on a wilted appearance as root system is limited. If the seed is directly in the zone and ammonia has leaked upward, the seed may start to germinate but will die.

When ammonia is injected into the soil, it moves outward from the injection point. This forms an oval or circular shape of ammonia release in the soil. The greatest concentration is at the point of release and lessens outward from this point.

Situations which growers should be aware of are conditions which may cause ammonia not to seal. This may occur on coarse-textured soils or soils which are too wet or dry. Ammonia will move back up the knife slot if not properly sealed and have a higher potential of injury as seed may be placed in this zone.

Winged sealers immediately above the outlet of the knife can help prevent ammonia movement upward. Also, be sure to place ammonia deep enough into the soil. Injury comes from free ammonia coming in contact with the seed and roots.

For more information, contact Wayne Flanary at 660-446-3724 or Heather Benedict at 660-425-6434, Regional Agronomists, University of Missouri Extension.