After last year’s drought, I didn’t think I’d see water logged fields this spring. But there’s water standing in fields all along the I-29 Corridor in South Dakota. Over the last five days, some areas have received more than 6 inches of rain.
How long can corn and soybeans plants at early growth stages survive in these waterlogged soils?
Nathan Mueller, South Dakota State University Extension agronomist, says it depends.
"We know that the crop growth stage, variety/hybrid, duration of ponding/saturation, soil type, soil/air temperature, and other factors can affect the survival of corn and soybean plants under these waterlogged conditions," he says in state issued by SDSU Extension. "Unfortunately other factors reduce plant population related to flooding including crusting, plants covered in sediment or buried under residue, and increase in seed/seedling diseases like damping-off in soybean."
Currently, the crop growth stages of most corn and soybean range from germination to V3 and germination to V1, respectively. At these early growth stages of germination, emergence and early vegetative, Mueller says both corn and soybean plants are negatively impacted quite quickly by waterlogged conditions.
"Crops that are not completely submerged have some limited capacity for diffusion of oxygen to occur from the shoot to the root, which increase survival time," he says. "Oxygen is needed by plant cells for growth and development including germination."
Mueller points to research data which shows that waterlogged conditions experienced by corn seed for two or more days is a long enough time to decrease final corn emergence and is more detrimental at soil temperatures in the 70s than the 50s.
"In general, young corn plants can survive about two to four days of flooded conditions," he says
Although the effect of waterlogging on soybean germination and early growth has not been widely studied or written about. Mueller says the presence of waterlogged soils at any time and for any duration during the germination process in soybeans will reduce the final germination and emergence percentage.
"A germination decrease of 20-43% can occur from a 48-hour flooding that occurs after the start of seed imbibition or swelling. Even after waterlogged conditions are removed, researchers have found that seedling growth was reduced by more than 50% from 24 to 48 hours of flooding when temperatures were near 77°F."
On-farm research and observations also say not to give up hope as soybean plants at the V2-V3 growth stage can survive on soils flooded up to eight days.
" If enough plants survive the temporary soggy conditions, yields in depressional areas can be equal to or better than upland areas during dry summers," Mueller says.
Soybean yield reductions from 0 to 100% can occur from three days of flooding at the V2 to V3 stage compared to adjacent non-flooded areas. However, he says low plant populations and shorter plants resulting from ponding/flooding often result in decreased yield. The probability of yield loss increases as final soybean plant population decreases below 100,000 plants/acre.
Mueller says there should be plenty of seed available in the maturity range needed to replant, but may not be able to get the extra hybrid of variety you want.
If you can’t plan, you’ll probably want to check out the prevented planting provisions in the Farm Bill. See http://www.extension.iastate.edu/agdm/crops/html/a1-57.html. You’ll also need to know the final planting dates for crop insurance coverage. For South Dakota data, see http://igrow.org/agronomy/corn/late-planting-dates-for-crop-insurance/.