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fingers holding two corn kernels, one of which has reached black layer
RACE TO MATURITY: The kernel on the left shows the black layer at the tip, while the kernel on the right from a different ear is still not quite to black layer.

Corn finally reaches black layer

Corn Watch: One of the two hybrids in the field didn’t reach black layer until early October.

Finding a black layer on kernels this year was almost like finding the pot of gold at the end of the rainbow. For a while, it appeared as if this final growth stage might be that elusive. Late planting and periods of cool weather interspersed among very hot days left many people wondering if corn planted in June would mature before frost.

Many hoped for a late frost. As it turned out, frost came at about the normal time in most areas of the eastern Corn Belt. A killing freeze didn’t occur until Nov. 1 on average, which is close to normal for many of these same areas. As a result, most fields of corn, even those planted well into June, matured before a killing freeze.

Dave Nanda, director of genetics for Seed Genetics-Direct, explains that in a corn breeder’s terms, that means kernels reached physiological maturity. When that happens, a layer of cells forms at the tip of the kernel that prevents materials from entering or leaving the kernel. Since it usually has a dark tint, it’s often referred to as the black layer.

Once corn reaches that point, yield should not be affected even if a 28-degree-F killing freeze occurs. However, grain moisture could still be at 30% to 32% when black layer first occurs.  

Corn Watch ’19 field

Seed Genetics-Direct sponsors Corn Watch ’19. The goal was to follow the season by monitoring how one field of corn in central Indiana reacted to the environment during the season.

There was no guarantee the Corn Watch ’19 field would reach physiological maturity before a frost or killing freeze either, Nanda notes. It was planted May 28 with two mid- to full-season hybrids.

“Everyone was three to four weeks behind in the field all season long,” Nanda says. “The Corn Watch field was well above knee-high by the Fourth of July, but it didn’t pollinate until at least a couple weeks after that date.”

Nanda started looking for signs of black layer in early September. “When we first started looking, it was still in the dough stage, just coming out of the milk stage,” he recalls. One of the hybrids was a few days ahead of the other one on maturity.

The earliest of the two hybrids finally reached black layer in the waning days of September. The other hybrid was about a week behind. Fungicide was applied on the field, which helped plant health and possibly added to yield, but plants of the later hybrid stayed green even into October.

Nevertheless, both hybrids finally reached black layer. The first 36-degree frost occurred in mid-October, which is normal based on 30-year averages for the area.

“Hopefully we won’t be so anxious about examining kernels for black layer next year,” Nanda concludes.    

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