Cold, snow at start of May could injure corn seeds

COLUMBIA, Mo. –Plummeting temperatures in Missouri could mean poor stands of corn and seed damage.

The unseasonable weather might cause chilling injury to corn seeds prior to emergence, said University of Missouri Extension agronomy specialist Bill Wiebold.

Seeds contain 6-8 percent moisture when they go into the ground, then they rehydrate themselves with moisture from the soil. At low temperatures, the hydration process can rupture seed cell membranes. Cell contents can then leak out and become a food source for invading pathogens, leading to death or injury of the seed.

“It can be devastating,” Wiebold said. Damage during seed imbibition could take out 90 percent of the stand, he said. “We’re going to see it happen this year. Be ready to think about replanting. Seed in the bag is usually not affected by cold temperatures.”

Emerging seedlings may also face field conditions such as crusting. No-till fields typically have lower soil temperatures and greater soil moisture. Well-drained soils fare better than claypan soils.

Producers who haven’t planted corn yet are feeling pressure to start soon to avoid yield losses. Wiebold and MU Extension corn specialist Brent Myers said there is still time to get high yields.

“We’re not at the point where we’re getting significant yield loss yet,” Myers said, “but we’re getting close.”

Declines in yield potential may occur soon, but they will be small until after mid-May.  Corn yield begins to drop when planted after the end of April, but only by 5 percent by May 5 and 13 percent by May 20, according to data from a four-year planting-date study at MU’s Bradford Research Center near Columbia. Yield drops as much as 40 percent when corn is not planted by June 19.  Wiebold and Myers also recommend that farmers stick with 110-day maturing corn through the end of May.

When soil temperature remains below 50 degrees, seeds germinate slowly and can take three to four weeks to emerge.

The U.S. Department of Agriculture’s April 29 planting progress report remained virtually unchanged from the last update, with only 15 percent of Missouri’s corn crop in the ground, most of that in the southern part of the state. This is 24 days behind last year and 15 behind normal, but doesn’t reflect recent planting activity in northern counties.

Temperatures remained 5-9 degrees below average across the state. The four-week average for rainfall was 6.22 inches, with areas in northeastern Missouri getting as much as 7.51 inches.

“This is a spring for the record books,” Wiebold said.

The MU Extension guide “Corn and Soybean Replanting Decisions” (G4091) is available for free download at extension.missouri.edu/p/G4091.