No one knows the unpredictability of Iowa weather better than Iowa's own corn and soybean producers. Previous thoughts of early-season drought quickly have turned to concerns about flooding and saturated fields. Most of the corn acreage across the state has been planted and recent rains have raised questions regarding the survivability of small corn plants exposed to saturated or flooded conditions. Flooding does reduce corn yields, either by decimating stands, slowing dry matter accumulation, or both. Corn has been shown to be more susceptible to flooding injury than either soybeans or sorghum.
Warm temperatures exacerbate the injury.
As the plants increase in size, their susceptibility to flooding lessens, but there still can be yield reductions as a result of the flooding. Other problems also may arise, such as fungal pathogen infection. Excess moisture and flooding provide ideal conditions for the development of seedling pathogens, especially Pythium species. Flooding probably reduces the half-life of the fungicidal seed treatments, too, although there are no hard data to quantify this effect. After the flooding subsides, you can expect some surviving plants to collapse later due to fungal infection.