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College of Food, Agricultural, and Environmental Sciences


Rains May Hold Up Corn Crop

May 27, 2004

COLUMBUS, Ohio — Despite recent scattered thunderstorms with heavy downpours and hail, nearly three-quarters of the state’s corn crop remains in good-to-excellent condition, according to the Ohio Agricultural Statistics Service. But it’s the saturated soils and ponding of some fields that raise questions as to what condition the crop is headed. Peter Thomison, an Ohio State University Extension agronomist, said that saturated soils and ponding — localized for much of Ohio — may have an impact on the corn crop in that oxygen depletion caused by flooded conditions can impair nutrient and water uptake and inhibit root growth. “Growers should keep such factors in mind when evaluating damage from saturated soils,” said Thomison. “The extent to which flooding injures corn is determined by several factors including plant stage of development when flooding occurs, duration of flooding and air/soil temperatures. When you have warm temperatures (above 77 degrees Fahrenheit), corn may not even survive 24 hours.” Even if the plants survive flooded conditions, there could be problems later in the growing season. “Excess moisture during the early vegetative stages retards corn root development,” said Thomison. “As a result, plants may be subject to greater injury during a dry summer because root systems are not sufficiently developed to access available subsoil water.” The stage of corn throughout Ohio currently ranges from V1 to V6 (the stage at which the growing point of the plant is at or above the soil surface). About 85 percent of the corn has been planted in Ohio, with areas mainly in the north central and northeast regions of the state still waiting to plant. Thomison said some growers may be forced to plant later than normal or replant their crop due to soil conditions. “If growers are in a late-planting or replant situation, they may want to take a look at Bt corn hybrids. We’ve seen advantages in planting Bt corn late in the season as a control for European corn borer,” said Thomison. “Late-planted fields are more susceptible to second generation damage from corn borer. If a grower has to replant and can’t plant for another week and has to stay in corn, it may be a good option to look at Bt corn, especially if he can get the right hybrid maturity.” Thomison said growers can usually plant corn up through the first week of June, at which time they are encouraged to switch to another crop, like soybeans. Those growers that are dealing with saturated soil conditions in their fields should be evaluating the condition of their corn crop. “Take at look at the regrowth that is occurring. Cut the plant open and look at the growing point. If it’s dark color and mushy, it’s likely that the plant will either die or be unproductive,” said Thomison. “Sometimes when a plant sits in a saturated condition for prolonged periods, the growing point of the plant dies, but you get suckers that grow from the growing point below-ground nodes. This results in an unproductive plant that usually does not produce normal ears. In fact, I’ve never seen a normal ear develop from a sucker.” Where a corn plant, in its early stages of development, is vulnerable to saturation damage, hail generally does little in impacting the plant’s performance. “The corn crop up through the V6 stage is usually impervious to defoliation damage from hail storms and hail does little to impact yields,” said Thomison. “One exception is when you get hail damage on top of saturated soils. The water splashes into the damaged whorls of the plant, depositing dirt and bacteria. That bacteria grow within the plant and eventually kill it. Warm dry weather following a hailstorm will facilitate rapid re-growth. However, cool, cloudy weather that stops plant growth will give bacteria and fungi in the whorl more time to invade and infect the growing plant.” State precipitation as of May 24 was averaging 2.37 inches, 1.51 inches above normal. Some counties were hit hard with recent severe thunderstorms, with Medina reporting the highest amount of rainfall for the week at 5 inches.

Candace Pollock
Peter Thomison