Considerations for flooded corn and soybean
With the recent heavy rains, many corn and soybean fields have areas where crops are experiencing flooded or saturated conditions. This article discusses agronomic and disease issues for corn and soybean exposed to prolonged periods of high soil moisture and cool temperatures.
Agronomic considerations for corn
Growth and development
Young corn can survive flooded condition lasting for about 2 days under warm temperatures (at or above mid-70ºF) to 4 days under cooler temperatures (at or below mid-60ºF). Survivability also is influenced by how much of the plant was submerged and how quickly the water recedes. Corn plants that survived flooded conditions should show new leaf development within 3 to 5 days after water recedes.
Flooding and saturated conditions also restrict root development, thereby reducing the crop's ability to take up water and nutrients and tolerate drought stress later in the season.
Additional information is available from Purdue University in the article,
Effects of flooding or ponding on young corn.
The University of Minnesota Extension corn replant guide is available at: http://www.extension.umn.edu/agriculture/corn/planting/docs/corn-field-guide-evaluating-crop-damage-replant-options.pdf.
In general, corn should not be planted for grain after mid-June in Minnesota. According to the research summarized in the corn replant guide, expected yield of corn planted on June 19 is 59% of maximum. Further, corn planted in mid-June or later is at high risk of being frozen in the fall prior to corn physiological maturity, even if an early-maturity hybrid is selected.
At this time, growers in Minnesota that wish to replant should consider planting a crop other than grain corn. however, corn planted for silage can generally be planted as late as June 25 in southern Minnesota, if hybrids are selected that are 15 or more relative maturity units earlier than full-season for the region.
Nitrogen management considerations
Wet soil conditions in the spring create concerns that nitrogen (N) applied in early spring or earlier might be lost. When soils become too wet, the potential for N losses is directly related to the amount of N present in the nitrate (NO3-) form. With the exception of urea-ammonium nitrate (UAN) solutions that contain 25% of the total N as nitrate or ammonium nitrate that contains 50% of the total N as nitrate, most commercial fertilizers being used today are in the form of ammonium (NH4+) or forms that rapidly transform to ammonium (like anhydrous ammonia and urea). In the ammonium form, N is retained in the exchange sites of soil particles and organic matter.
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