Some of Ohio’s soybean fields are facing flooding injury due to heavy rains that have swept across the state over the past few weeks, but the injury is not likely a total loss to the crop.

“Soybean plants subjected to flooded conditions get stunted and stay short the rest of the season,” said Anne Dorrance, an Ohio State University plant pathologist with the Ohio Agricultural Research and Development Center (OARDC). “Fewer pods also develop, which reduces yields, but it’s not a 100-percent loss.”

According to studies conducted by Ohio State University soybean researchers and OSU Extension Educators, soybean plants sitting in one to two inches of water for up to a week take anywhere from a 20 to 50 percent yield hit, depending on the variety and the drainage situation in the field.

“We have seen in some of these studies plants recovering in places where the field does get to dry out and temperatures don’t get too hot,” said Dorrance. “But we also have places were the plants are just wiped out.”

Because of the flooding conditions in some areas of the state, fields have been replanted, and a growing concern if rains continue is that it will become harder for plants to recover because of the presence of diseases. Saturated conditions have opened the door for diseases, such as Pythium and Phytophthora root rot.

“What will be even worse is if the faucet shuts off altogether. Plants are already faced with damaged root systems, and if we go into a drought, then it’s a double whammy,” said Dorrance.

Growers can distinguish flooding injury from diseases by observing the condition of the plant roots.

“First of all, there will be a smell. The field will smell different because there is so much decay, and it’s because the roots have been suffocated. Then when you dig up the plants, if the skin sloughs off the root exposing the white center, you’ve got flooding injury,” said Dorrance. “If the entire root system just turns to mush, then you’ve got root rot.”

Improved field drainage, resistance packages and seed treatments are ways growers can combat disease development on their soybean plants when conditions become favorable.

Corn at less-vulnerable stage

The corn crop throughout parts of the state was also subjected to flooding conditions, but its development is at a point that makes it less vulnerable to flood damage.

“Corn planted before May 10 is probably well beyond the V-5 stage when the growing point is at or below the soil surface and more sensitive to flooding and associated anaerobic soil conditions,” said Peter Thomison, an OSU Extension agronomist.

One concern is that immersed corn plants were covered with layers of silty mud, potentially inviting diseases that could affect the crop’s performance.

“The layers of silty mud covering plants will limit or prevent leaf photosynthesis. Bacteria deposited in leaf whorls by flooding can result in disease and kill plants,” said Thomison, who also holds a partial OARDC research appointment. “However, most corn development in the state has not progressed beyond the 10- to 11-leaf collar stage so most leaves on affected plants should not be severely impacted by the mud coatings. Corn plants produce up to 21 leaves, so at the 10- to 11-leaf collar stage, about half the corn leaves have yet to emerge from whorl.”

The leaves of the upper canopy are considered the most important for the corn plant, because they produce most of the plant’s yield potential.

For weekly updates on Ohio’s field crops, see the Crop Observation Recommendation Network (C.O.R.N.) newsletter.