Ag Answers:Osu Study Shows Hail-damaged Crops Still Produce

Scientists can't stop hailstorms. But it might not matter anyway, because corn defoliated by hail early in the season recovered fairly well in an on-farm agronomy study conducted by Ohio State University.

Researchers cooperating with local farmers studied the recovery of corn plants virtually shredded in a June 9, 2000, storm that pelted Fayette County, Ohio. Hailstones ranged in size from 0.75-inch to 1.25 inches. Some plants were 80 percent to 100 percent defoliated.

"When I got down there a few days later, the farmers said the ground had been completely white with hailstones," said graduate student Todd Mangen, who conducted the project with OSU agronomist Peter Thomison. "They said it looked like it had snowed. They didn't think the crop would produce anything at all."

But survive the crop did. Yields in three of the four fields approached or surpassed the state's record corn yield average of 149 bushels per acre. Yields at the best sites ranged from 147.5-194.1 bushels per acre, while the worst site checked in at 93.3 bushels per acre. "The recovery rate was phenomenal," Mangen said.

It also was a rare opportunity for agronomists to study stalk bruising from hail impact, Thomison said. Researchers often don't study corn defoliation from a real-world hail event, he said. Usually they simulate defoliation by manually removing leaves from plants. Hail impact can cause other kinds of damage, such as stalk bruising.

The study found that hail bruising didn't weaken stalks nor lead to significant losses from lodging, Thomison said. The outcome refuted growers' perceptions that bruised tissue would be susceptible to disease or insect damage, resulting in stalk rot, he said.

Thomison attributed the corn crops' recovery to the excellent growing conditions after the hailstorm. Another factor was the position of the plant's "growing point" relative to the ground. The growing point is a pyramid-shaped whitish stalk tissue near the base of the seedling. Plants seem to recover well when the growing point is at or near the soil surface when the hail falls.

Knowing the potential for plant recovery is valuable to farmers who have to make split-second management decisions about what to do with damaged fields, Thomison said. The decision can be very subjective because defoliation isn't pretty and can be downright terrifying to a farmer concerned about a crop loss. Producers can save the time and expense of replanting to a short-season crop like soybeans if they know the crop has a reasonable chance to recover.

Another value of defoliation studies is that management decisions can be applied to other kinds of events that remove leaves from corn or affect their full functioning, Thomison said. These include severe insect feeding, foliar disease and chemical or mechanical damage.

Understanding how corn develops after a defoliation event can help farmers troubleshoot plant abnormalities found later in the season, Thomison said. For example, farmers with widely dispersed fields may not be aware that localized hail affected their crop when they come across barren plants, excessive tillering or tied whorls, all associated with hail damage.

There are secondary management considerations when defoliation occurs early in the season, Thomison said. They include:

* Uneven maturity rates between defoliated and unaffected corn, resulting in varying drydown rates throughout a field.

* Ears of defoliated plants closer than normal to the ground, requiring equipment adjustments at harvest.

* More weed problems because defoliated plants don't close the canopy early enough to shade out weeds.

* Tied leaf whorl or "buggy-whipping" syndrome, whereby the leaf whorl is twisted, preventing leaf emergence after a hailstorm.