First frost of the season should not affect harvest, expert says

Eastern Iowa likely will see its first frost of the season overnight, followed by the possibility of freezing temperatures Tuesday night into Wednesday.

Brian Pierce, a meteorologist with the National Weather Service in Davenport, said the first frost in Eastern Iowa typically occurs during the first 10 days of October, so the Cedar Rapids area is “roughly right on schedule.”

Cedar Rapids itself “is kind of right there on the edge of possibly seeing frost,” he said.

The National Weather Service has issued a frost advisory for Eastern Iowa from 1 to 8 a.m. Tuesday with temperatures between 32 and 35 degrees. It has placed the area under a freeze watch from Tuesday night into Wednesday morning, where lows in the upper 20s are possible.

Since chilly conditions could be on hand for the next few mornings, Pierce said gardeners should take measures to protect sensitive plants, like moving them indoors.

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Joshua Michel, an Iowa State University Extension and Outreach field agronomist for Northeast Iowa, said there is not too much concern about frost conditions interfering with the harvest.

“As far as grain harvests for corn and soybeans, the harvest season is already so far along that a lot of the fields in Northeast (and) Eastern Iowa are already being harvested or will be harvested shortly,” Michel said.

Michel said the only danger for the frost affecting harvest would be for any corn or soybeans that were planted late in the season and haven’t reached maturity yet.

“But those are very few and far between,” Michel said. “If there are any fields like that, then a frost event will essentially force those plants to shut down … wherever they are in growth and development. But thankfully, that's going to be very, very limited.”

Michel said when he surveyed Northeast Iowa last week, the number of times he saw corn and soybean crops “shut down” on fields could be counted on one hand.

How can frost affect other plant species?

Michel said he is more concerned about the frost affecting cover crops and forages in northeastern and eastern parts of the state.

Michel said cover crops like oats and turnips could be killed off due to the frost. Cereal rye, on the other hand, has more “cold hardiness” to withstand chillier temperatures.

One other risk, he said, is with forages grown to feed livestock, specifically with sorghum species. Michel said when stress — like that resulting from colder temperatures — is placed on these plants, they can produce prussic acid that can result in “acute toxicity” for livestock who eat it.

“As of now, thankfully, there's pretty limited production of these particular sorghum species throughout Eastern Iowa, but there are a few out there,” Michel said.

Michel said alfalfa and clover do not have prussic acid and are not considered toxic, but when they are eaten by livestock after a frost, there is a slightly higher risk for bloat.

“If a producer does want to allow their livestock to go out and graze it, they should follow some normal bloat preventing grazing management, just to try to help prevent any potential issues,” Michel said.

Olivia Cohen covers energy and environment for The Gazette and is a corps member with Report for America, a national service program that places journalists in local newsrooms to report on under-covered issues.

Comments: (319) 398-8370; olivia.cohen@thegazette.com