This year seems to have been a lucky one so far. The corn across most of the country has hit the fairly safe zone, says Jeff Coulter, University of Minnesota extension corn specialist.
A heavy frost would only reduce yield by 10% since most of the corn in the country is in the half-milk stage or further along. A light frost, which only affects the leaves, would only reduce yield by 5%, he says.
The severity of the damage depends on the length of time and the extent of the below-freezing temperatures, according to Iowa State University's National Corn Handbook. Substantial damage would occur if the temperature remained below freezing for four to five hours. Leaves are most susceptible to frost because of their whorl arrangement and thin composition, making it difficult to retain heat.
The best and only thing a farmer can really do for corn that has been hit with a frost is to simply hold off and let it dry down, says Coulter. Once it dries down, the farmer can take it out of the field.
Farmers should check the field the morning after a frost once the sun has risen and started thawing the plant, according to the National Corn Handbook. The bigger issue is to plan ahead for next year, Coulter says.
Coulter's advice for future years is to avoid pushing the maturity because it only takes one bad year to cause problems. Farmers should choose plant corn varieties that are reasonable for their areas. Corn hybrids should be chosen based on when they reach physiological maturity, according to the National Corn Handbook. The plants should reach maturity before the average date there is a freeze risk greater than 50%.
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