Despite the latest reports that 69% of the Illinois corn crop is in good or excellent condition, excessive rains in some areas of the state have farmers downgrading their dreams of a record harvest.
Plants left standing in flooded fields with stunted growth, yellow leaves, shortened internodes and symptoms of nutrient deficiencies are likely to show little or no recovery, says Emerson Nafziger, University of Illinois Extension agronomist.
“Once internodes are ‘set’ with hardened cell walls, no more cell expansion is possible and internodes will stop growing,” Nafziger says. “It’s the same story with leaves; small leaves will stay small once two or more leaf collars appear above them.”
If the soil would dry up some, existing leaves could green up and growth rates could increase, restoring some yield potential if the developing ears have not been compromised too badly, he says.
The real deficiency suffered by plants standing in wet or saturated soils is the lack of oxygen in the roots, not lack of nitrogen (N) in the plant. Nitrogen deficiency can’t be cured as long as oxygen deficiency exists.
“Applying foliar forms of N or dry forms such as urea will not do much good until the water goes away and the roots start to take up oxygen,” he says. “Roots do more than just take up nutrients; they produce plant hormones, they grow into the soil to reach more nutrients and they anchor the plant. They do none of these things well when they are sitting in saturated soils unable to take up oxygen. In addition, plant roots release carbon dioxide, which builds up in saturated soils and can poison the roots.”
Because of this, applying N will produce little benefit to plants that are severely stunted and standing in water, he says. However, if the majority of a field is on drier ground and still needs N, then it should be applied as soon as possible.
Nafziger recommends applying N to corn in low, wet areas only after the water is gone and plants start to green up, which indicates they are getting some oxygen. If plants are stunted and far behind the rest of the field, applying N may not help.
“I don’t recall seeing severely stunted, deficient plants standing in saturated soils come back to produce much yield,” he says. “That’s not proof it can’t happen, but the deck is stacked against these plants. Applying more inputs may be a demonstration of more hope than is justified.”
For more information on salvaging flooded corn, read The Bulletin, an online publication written by U of I Extension specialists in crop science.