Harvest consideration for frost killed corn

Oct 10, 2019

By Mark Licht, Charles Hurburgh

A portion of Iowa’s corn crop is likely to experience a frost before naturally reaching maturity as a result of cool temperatures later this week. Natural maturity is often determined when a black layer is formed at the kernel tip. At this timeframe grain moisture is typically 28–35% moisture. If a frost or freeze occurs a black layer can still form, however, grain moisture will be greater than 35%. A light frost of greater than 28oF for only a couple hours may kill some leaves, especially in the upper canopy. A freeze of 28^oF or less for a couple hours will result in whole plant death.

Whether maturity is natural or induced by a frost, grain dry matter accumulation has finished. Incomplete grain fill from a frost or freeze often results in corn with low test weight that is greater than 35% moisture. The severity depends on how far the milk line has progressed at the time of the cold temperatures. At ¼ milk line the kernel moisture will be higher and the kernel weight will be lower compared to ¾ milk line. Expect dry down in the field to take longer because of a higher kernel moisture and slower dry down rates because there is continued moisture exchange with the cob.

Grain yield decreases more the earlier a killing frost occurs (ranges from 12% in late dent up to 41% at beginning dent stage). Yield losses are also less when only leaves are killed (ranges from 6% in late dent up to 27% at beginning dent stage). In addition to lower yield, incomplete grain will occur resulting in a lower test weight. Expect test weight to be in the low 50s to 40s (pounds/bushel). Lighter kernels will require fine adjustments to combine settings. Recognize the effects frost and freeze to corn ahead of natural maturity results in more susceptibility to breaking, lower grain protein, and lower digestibility

Grain moisture of frost injured corn is deceptively low because the outer portion of the kernel dries quicker than the interior. Often grain moisture is 1–2% higher than many grain moisture meters, however, the newer 150 mhz units used by many elevators are more accurate. Dry frost killed corn 1–2% lower than the typical 14–15% and cool grain as quickly as possible. It will take more energy per unit of moisture removed to dry frost damaged corn. Storage life drops rapidly below 53 pounds/bushel test weight.

Source : iastate.edu

Video: Why Your Food Future Could be Trapped in a Seed Morgue

In a world of PowerPoint overload, Rex Bernardo stands out. No bullet points. No charts. No jargon. Just stories and photographs. At this year’s National Association for Plant Breeding conference on the Big Island of Hawaii, he stood before a room of peers — all experts in the science of seeds — and did something radical: he showed them images. He told them stories. And he asked them to remember not what they saw, but how they felt.

Bernardo, recipient of the 2025 Lifetime Achievement Award, has spent his career searching for the genetic treasures tucked inside what plant breeders call exotic germplasm — ancient, often wild genetic lines that hold secrets to resilience, taste, and traits we've forgotten to value.

But Bernardo didn’t always think this way.

“I worked in private industry for nearly a decade,” he recalls. “I remember one breeder saying, ‘We’re making new hybrids, but they’re basically the same genetics.’ That stuck with me. Where is the new diversity going to come from?”

For Bernardo, part of the answer lies in the world’s gene banks — vast vaults of seed samples collected from every corner of the globe. Yet, he says, many of these vaults have quietly become “seed morgues.” “Something goes in, but it never comes out,” he explains. “We need to start treating these collections like living investments, not museums of dead potential.”

That potential — and the barriers to unlocking it — are deeply personal for Bernardo. He’s wrestled with international policies that prevent access to valuable lines (like North Korean corn) and with the slow, painstaking science of transferring useful traits from wild relatives into elite lines that farmers can actually grow. Sometimes it works. Sometimes it doesn’t. But he’s convinced that success starts not in the lab, but in the way we communicate.

“The fact sheet model isn’t cutting it anymore,” he says. “We hand out a paper about a new variety and think that’s enough. But stories? Plants you can see and touch? That’s what stays with people.”

Bernardo practices what he preaches. At the University of Minnesota, he helped launch a student-led breeding program that’s working to adapt leafy African vegetables for the Twin Cities’ African diaspora. The goal? Culturally relevant crops that mature in Minnesota’s shorter growing season — and can be regrown year after year.

“That’s real impact,” he says. “Helping people grow food that’s meaningful to them, not just what's commercially viable.”

He’s also brewed plant breeding into something more relatable — literally. Coffee and beer have become unexpected tools in his mission to make science accessible. His undergraduate course on coffee, for instance, connects the dots between genetics, geography, and culture. “Everyone drinks coffee,” he says. “It’s a conversation starter. It’s a gateway into plant science.”