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Flooded corn

Heavy rains can flood corn fields or create saturated conditions. Here, we discuss agronomic and disease issues when corn is exposed to prolonged periods of high soil moisture and cool temperatures.

Agronomic considerations

Growth and development

Young corn can survive flooded conditions lasting for about two days under warm temperatures (at or above the mid-70s, in degrees Fahrenheit) to four days under cooler temperatures (at or below the mid-60s).

How much of the plant was submerged and how quickly the water recedes influences survivability. Corn plants that survived flooded conditions should show new leaf development within three to five days after water recedes.

Flooded and saturated conditions also restrict root development, reducing the crop's ability to take up water and nutrients and tolerate drought stress later in the season.

How flooding or ponding affects corn prior to tasseling

Replanting

University of Minnesota Extension corn replant guide

In general, do not plant corn for grain after mid-June in Minnesota.

When planted on June 19, expected corn yield is only 59 percent of the maximum. Plus, corn planted in mid-June or later has a high risk of getting frozen in the fall before it reaches physiological maturity, even if an early-maturity hybrid is selected.

If you wish to replant at this point, consider planting a crop other than grain corn. However, you can generally plant corn for silage as late as June 25 in southern Minnesota, if you select hybrids that are 15 or more relative maturity units earlier than full-season for the region.

Nitrogen management considerations

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Seedling diseases

Flooded and wet soil conditions increase the risk of seedling diseases (Figure 3), which may become a problem in flooded fields.

Favorable conditions for seedling diseases include wet and compacted soils, slow plant emergence and growth, crusted soil and poor seed quality.

Diseases can reduce plant and root growth, plant population and, ultimately, yield. Non-lethal infection at the seedling stage may cause damage that persists through the growing season.

rotting corn seedling
Figure 3: Corn seedling disease.

Problematic pathogens

The soilborne pathogens that cause these problems are widespread and persistent in Minnesota fields, and can cause damage when conditions develop that favor them. Several different pathogens and diseases can become problematic.

For example, wet and flooded soils are especially favorable for the soilborne, moisture-loving pathogens like Pythium, which appears to cause most damage to corn and soybean seedlings.

Jeff Coulter, Extension agronomist; Seth Naeve, Extension agronomist; Dean Malvick, Extension plant pathologist and Fabian Fernandez, Extension nutrient management specialist

Reviewed in 2018

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