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How to Tell When Corn is Physiologically Mature

How to Tell When Corn is Physiologically Mature
Look for the black layer at the tip of the kernel to know for sure.

Earlier in the season, during cool spells in late July and early August, it appeared that some later-planted corn fields might have trouble reaching black layer before frost. As long as the frost isn't early, at least not a killing frost, that no longer seems as likely. An increase in heart in late August and early September, plus dry weather that affected plants, has led to plants maturing faster than it once looked like they would.

However, that doesn't mean that every field in Indiana has reached black layer yet. And when it does, it can still be very wet corn, usually from 30 to 35% moisture at black layer, according to Bob Nielsen, a Purdue University Extension corn specialist.

Black layer formed: Look closely at the tip of the kernel. You can see a black layer which has just formed in the past few days on this kernel.

So how do you tell if your corn has reached black layer? Danny Greene of Greene Crops Consulting, Inc., Franklin, says the best way is to break an ear in half and examine the kernels. Pull out your pocketknife and carefully work toward the tip of the kernel.

As you get toward the tip, you will see different layers of material, depicting layers of starch that have been laid down as the kernel began to mature. Finally, if the corn has black-layered, you will find a rather thin but distinctive clack layer, almost a line, of material at the base of the kernel. If the kernel has reached black layer a few days earlier, the black layer may be more pronounced than if it is just now reaching that stage.

It's significant, Greene says, because once the black layer is laid down, the kernel no longer accepts any more sugars to add to kernel weight. Likewise, no more materials can be pulled out of the kernels to be used elsewhere in the plant, either.

TAGS: Extension
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