Flooded fields are prevalent around the Corn Belt, some planted, and some are not. Iowa State agronomists say corn that is germinating can withstand four days of saturated or flooded soils. Seedlings with less than six leaves can withstand four days underwater if the temperature is less than the high 70’s. Higher temperatures shorten the survival period.
As floodwaters recede decisions about replanting need to be made, but the feasible dates for replanting are quickly vanishing. In the next few days, replanted corn may have a 90% yield potential, but if replanting is delayed beyond June 10, the yield potential is 70% or less. Consult the Iowa State Extension website.
Soybeans are jeopardized by wet fields says Palle Pedersen at Iowa State since there is significant yield loss after six days in the water, and greater yield loss with temperatures over 80 degrees. Saturated soils restrict oxygen to the soybean roots, and flooded soils allow a build up of toxins and carbon dioxide 50 times greater than in dry soils. Silt can also collect on leaves and restrict photosynthetic activity, unless rain washes it off.
If your soybeans are emerging,what is their state of health? Iowa State specialists say poor stand establishment suggest disease pressure is quite high despite use of fungicides. Cool wet soils increased seedling diseases and contributed to the poor emergence rate.
If your soybeans need replanting,seed treatments with fungicides are highly recommended by specialists, who say, “If Phyophthora causes seedling damping off, more severe damping off would happen in the replanted soybeans unless the seed is treated with the right fungicides or the weather turns dry after replanting.” And the recommendation is for the use of even higher doses of fungicides on the replanted beans.If your soybeans are planted and up,they are susceptible to damage from bean leaf beetles, because they are starving and looking for food. Large numbers can accumulate in the few fields which have growing soybeans. Bean leaf beetles have to be numerous (16-39 beetles/ft. of row at stage V2+) to cause economic damage. But they say with soybeans struggling to grow, and considering the value, lower thresholds may work.