Many corn and soybean fields are submerged in water after heavy rains swamped portions of north central Ohio earlier this week. Ohio State University Extension agronomists are still evaluating the impact of potential flood damage, the effects of which are dependent on stage of crop development, length of the flooding period, speed of water movement, and other factors.

"Late-season flooding is an uncommon event in Ohio, so little information is available on its effects on corn at this stage of development," says Peter Thomison, an OSU Extension agronomist. "A major concern is the impact of flooding on grain and silage quality."

According to the Ohio Agricultural Statistics Service, over 75 percent of the corn crop is in the dough stage, and nearly 25 percent is denting.

"In past reports, when corn in the dent stage was covered by floodwater for six or more hours and nearly completely caked with mud for up to two weeks, damage from ear rots and premature kernel sprouting was extensive in those areas of fields where water had covered the ears the longest," says Thomison, who also holds a partial Ohio Agricultural Research and Development Center appointment.

The impact of flood damage on corn will be highly dependent on stage of development, duration of the flooding, how much the corn plant was immersed during flooding, and subsequent weather conditions.

"Prolonged flooding may cause significant root injury. Such plants will be more vulnerable to stalk rots, thereby increasing the likelihood of stalk lodging, especially if harvest is delayed," says Thomison. "As soon as plants have dried, stalks should be inspected to determine if root rot has indeed occurred and to what degree."

He recommends that infected fields be harvested first to minimize yield loss.

The position of the ears when the plants were flooded can also contribute to potential plant injury.

"If ears were in an upright, rather than downward position, it would have probably resulted in them catching and retaining more soil. This can lead to ear rots because of the ears being caked with mud," says Thomison. "When dealing with flood-damaged corn, a common suggestion is to allow rains to wash off as much soil as possible before harvesting to retain silage quality, as well as help make harvesting a bit easier."

Flood damage to Ohio's soybean crop is also dependent on how much the plants were covered with water and for how long, amount of silt and debris contained in the water, and the speed of water movement.

"The minimum yield loss occurs when plants are only partially covered with clean water for no more than three days," says Jim Beuerlein, an OSU Extension agronomist. "The maximum damage occurs when plants are totally covered with dirty water and silt is deposited on the leaves, pods, and stems."

If silt is not washed off the plants within two days, the plants will die within a couple of weeks.

"The effect of flooding during the reproductive stage of soybeans varies from near zero to total loss," says Beuerlein. "Where plants are totally covered with dirty water, there will likely be a total loss. Plants that were only partially covered with silt may produce some yield if the water leaves soon and the flooded part of the plant wasn't killed."

Anne Dorrance, an OARDC plant pathologist, stressed the importance of draining saturated fields as soon as possible.

"If fields remain saturated under hot weather and we get carbon dioxide build-up, that's when injury can occur," says Dorrance. Based on university research by soil drainage specialist Tara Vantoai, carbon dioxide can build-up to toxic levels in flood situations, injuring plant roots.

"Despite the flooding, soybeans are pretty tough," says Dorrance. "In fact, many fields that received these heavy rains were in desperate need of it from the drought."

Although the flooding damage caused by the recent heavy rains may be a blow to producers in affected areas, OSU Extension agronomists emphasize that the acreage flooded areas represent only a small portion of the state's total crop.