Corn in many parts of Oklahoma is looking good, but physiological maturity of the crop is still weeks away and so producers need to be vigilant in terms of risk management, Oklahoma State University experts said. 

“Many of Oklahoma’s summer crops were going backward about July 1, but then most of the state received needed rainfall; those crops with enough maturity left in them were able to turn a corner and recover,” said Josh Lofton, OSU Extension cropping systems specialist. “As of the last week of July, corn is still three to four weeks from physiological maturity.”

Corn producers can pick up visual cues from several crop development stages: 

• Most Oklahoma corn is in the kernel dent stage as of late July. Break open a cob and look for the milk line, a distinct horizontal separation between the milky and starchy areas of maturing kernels. The starchy area will have a more vibrant yellow color, while the milky area will be paler in hue. 

•  Physiological maturity of corn occurs shortly after the kernel milk line disappears and just before the kernel black layer forms at the tip of kernels. Stress after the crop reaches physiological maturity has little effect on grain yield unless the integrity of the stalk or ear is compromised. 

While not a grain development stage, harvest maturity is often defined as the point where grain moisture content is about 25% and harvest can occur with minimal kernel damage and mechanical harvest loss. There are issues with storing grain above 15% and grain buyers in the region often prefer corn producers delay harvest until moisture content is below 14% as most buyers do not have grain-drying capabilities.

An annual occurring issue with corn production in Oklahoma has been managing aflatoxin. Recent hot and humid weather conditions have been favorable for development of the greenish-yellow to yellow-brown fungus, often found on the ear between the kernels. Presence of the fungus is not always indicative of the amount of toxin produced.

OSU experts recommend producers contact their crop insurance agent if they suspect aflatoxins are going to be a concern before harvest. Aflatoxin contamination is an insurable loss, but strict protocols for sampling must be done during harvest and sent to an approved testing facility.

Lofton and Bushong recommend producers check their irrigation equipment to make sure it is working properly. 

“Remember, appearances can be deceiving; the corn crop is not quite at physiological maturity yet,” Lofton said. “Heading into August, there is still 10% to 30% of unrealized seed development to lose.” 

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