While the corn crop is planted and emerged in most Illinois fields, damage from both standing water and dry soils are causing stress to the crop in places across the state, said University of Illinois Extension agronomist Emerson Nafziger.

"Saturated soils cause both root damage and loss of N, meaning that plants are unable to take up enough N to keep healthy color," he said. "While pale leaves cannot photosynthesize as well as they should, pale color is mostly a symptom of the poorly functioning root system that results from low soil oxygen.

“In such cases, while supplemental N may provide some benefit, it will not do so until and unless soils dry enough to allow roots access to oxygen again."

Nafziger said several reports of "floppy" corn have also come in during the past two weeks from areas where soils had been dry for some time and plants were starting to grow rapidly.

"This is almost always a case where the nodal root system is trying, and failing, to grow out into the soil," he said. "This happens when surface soils are too dry to support root growth. In some cases a physical barrier, such as sidewall drying and hardening following no-till, also contributes."

Plants with this problem have outgrown the capacity of the seminal root system to support growth, and so they may fall over, due both to lack of physical support and to lack of water, he said.