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Timing and Temperature: Key Factors to Consider Before Replanting

Corn survival odds in flooded fields.

One way to describe the 2017 planting season? Soggy. If you have standing water in your planted fields, you may be considering replant. “Survival of young corn plants under these conditions depends on several factors,” says Roger Elmore, Extension cropping systems agronomist at University of Nebraska–Lincoln.

“Smaller seedlings are more susceptible than larger seedlings,” says Elmore in a University of Nebraska Crop Watch article. But the effect of standing water on germinating seeds is not well known. Hybrids will respond differently to standing water.

48 Hours

Timing is everything. If there’s standing water in your field, you have 48 hours before the oxygen supply will become depleted, says Elmore.

“Cool air temperatures help to increase the possibility of survival,” he says. “Yet, we would not expect survival of germinating seeds to be greater than that of young plants; they should not be expected to survive more than four days.”

Here are the odds for survival of young corn plants in varying conditions, according to the CropWatch article.

  • Before emergence: Seeds can survive up to four days.
  • Prior to the sixth leaf and underwater (6 inches of water on surface) with a temperature less than 77°F.: Will survive for four days. Longer flooding results in lower yields especially at lower nitrogen levels. Some plants will be buried by sediment and residue and may not survive.
  • Prior to the sixth leaf and underwater (6 inches of water on surface) with a temperature greater than 77°F.: May not survive 24 hours.
  • Corn prior to sixth-leaf stage in saturated, cold soil with flooding: Seed rots, seedling blights, various other pathogens, crazy top.

If it becomes necessary to replant, consider which herbicides have been sprayed, says Randy Hagen, knowledge transfer manager at Monsanto. “Some crops can’t be planted back to a field that had a certain herbicide.”

Don’t make a drive-by assessment either, advised Hagen. “Investigate the stands by going out and doing population stands in several spots of the field.”

Also, as we get closer to June, it’s time to start considering switching maturities. “If you have an option to do silage, you may want to go in and replant with the same maturity,” says Hagen. However, for grain, there may be a consideration to move to an earlier product. Hagen recommends looking at soil type, early frost dates, and yield potential of the of the original product before moving to an earlier maturity. If replanting goes into June, consider a hybrid five days earlier or so, he says.

Below are seven factors Elmore recommends considering when dealing with flooded fields.

  1. The longer an area remains ponded, the higher the risk of plant death.
  2. Completely submerged corn is at higher risk than corn that is partially submerged. Plants that are only partially submerged may continue to photosynthesize, albeit at limited rates.
  3. Corn will survive longer when temperatures are relatively cool — mid-60s or cooler — than when it's warm — mid-70s or warmer.
  4. Even if surface water subsides quickly, the likelihood of dense surface crusts forming as the soil dries increases the risk of emergence failure for recently planted crops.
  5. Extended periods of saturated soils after the surface water subsides will take their toll on the overall vigor of the crop.
  6. Associated with the direct stress of saturated soils on a corn crop, flooding and ponding can cause significant losses of soil nitrogen due to denitrification and leaching of nitrate N.
  7. In addition, diseases and other problems can develop due to silt in the whorls.
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