As I have driven around the countryside the last several days, I couldn't help but notice the typical scorched look of injured corn plants caused by ammonia gas escaping from poorly closed slots during sidedress nitrogen applications. What wasn't so typical was the random patterns of damage across fields, not just the usual end row damage where equipment turned around.
Not unlike the presence of leaf rolling , these random patterns of ammonia burn to corn leaves likely reflect the existence of severe soil compaction in many fields around the state this year. As the applicator knives are pulled through such areas, the slots often do not close properly due to the chunky clods being thrown up. Some ammonia escapes and dessicates corn leaves that happen to be in the way.
Luckily, the effects on grain yield from such defoliation to relatively young corn plants is relatively minor. The lower leaves being damaged are not important in the big scheme of things. Unless the whorl is damaged severely, new leaves will emerge within several days. Within a week or so, the damage will no longer be visible.