Producers who experienced flooding will have to evaluate crop damage due to flooding on a case-by-case basis, a South Dakota State University specialist says.
SDSU Extension Crops Specialist Bob Hall says there are many variables that affect flooding damage, so the extent of damage in a field can vary greatly. Each field or area of concern must be evaluated.
"The only sure statement is that crops totally and continually emerged for more that about three to four days or longer have a high risk for crop loss," Hall says. "A producer should go to the field, dig up plants, and look for good tissue. Off-colored or darkened tissues are likely early signs of seedling death."
Environmental temperature at flooding, including water temperature, has an effect, Hall says.
"Generally, the plant to tolerate flooding longer at cooler air and water temperatures. Flooding damage is also influenced by duration of the flooding period, whether the crop was totally submerged, which is worse, or only partially submerged.
Most reports indicate temperatures of about 77 degrees Fahrenheit as the cut-off temperature, Hall says. That is, temperatures above that level tend to hasten damage or plant death, while temperatures below that mark tend to enable the plant to cope with flooding longer.
Some researchers also think that plants under running water will tolerate flooding longer than plants under ponds of water, Hall adds.
At temperatures above about 77 degrees and total immersion, you can expect crop death within 12 to 24 hours, Hall said. At temperatures below 77 degrees and total immersion, the plants may hang on for two to four days with some reduction in stand.
"Plant seed also has to respire just like developing seedlings," Hall says. "The flooding of seeds will likely be somewhat similar to seedlings. Both the seedlings and seeds need to respire, and any lack of oxygen caused by flooding will sooner or later result in death."
Hall added that the tolerance of crops to flood conditions persisting longer than two days varies by crop type. Alfalfa is more tolerant than small grains, small grains are more tolerant than corn, and corn is more tolerant than soybeans.