Expert: Forget Corn Replant After July 110

With corn prices at record highs, many growers are considering replanting flood-damaged fields, although years of data advise caution with such a decision. Recent yield simulations run by the Department of Agronomy at Iowa State University show that while the economics may work out in a perfect situation, replanting carries with it some major risks.

“Corn planted this late has an early frost damage risk of around 40 percent in the southern part of the state and as high as 66 percent in the northern areas,” says Roger Elmore, ISU professor of agronomy and ISU Extension corn agronomist. “An early frost could mean the difference between 130 bushels an acre (bu/A) and 24 bu/A.”

Simulations of yield potential for corn acres planted by July 1 show early season hybrids will be the only reasonable option for anyone who finds it economical, and worth the frost risk, to replant. But planting the early season hybrids creates an additional risk since these varieties are less suited to Iowa’s environmental stresses and disease.

If the weather is perfectly suited to growing corn from now until harvest and land is replanted by July 1, it may be possible to reach yields of 100 bu/A to 130 bu/A. But grain moisture content could be as high as 37 percent which means yet another additional cost to dry down the harvest.

Given the high prices of other commodities besides corn, your growers should also consider the benefits of planting soybeans, grain sorghum, various spring and summer annual forage crops, or even leaving the land fallow, says Elmore.

“The yield potential for corn drops off precipitously every day planting is delayed,” says Elmore. “Our research shows a daily drop off in yield of 2.5 percent. And if you can’t plant before July 1, corn isn’t really an option.”

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