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Thinking about replanting corn? Think hard.

Farmers may be better off with poor stands than replanting.

As rain pushes corn planting season back yet again in some areas of the Midwest, farmers may be better off sticking with poor stands than replanting, says University of Missouri (MU) Extension agronomist Bill Wiebold.

Farmers face tough decisions about when and if they should replant corn, says MU Extension corn and small grains specialist Greg Luce. Start by weighing replanting costs with your head, not your heart, says Luce.

Compare current yield potential against replant potential and costs.
The MU Extension guide “Corn and Soybean Replant Decisions” tells how to count and calculate stands, replant costs, and yield potentials. The guide provides worksheets to help growers make decisions for different regions of Missouri. 

Wiebold’s research suggests that poor stands from earlier-planted corn may be the best option as it gets later in the season for replanting. “The later we get, the more acceptable the corn stand becomes,” says Wiebold.

“The health of the existing corn stand certainly needs to be considered,” says Luce, “yet it may be better to plant soybean than replant corn.”
Luce gives examples in a MU Integrated Pest & Crop Management newsletter article “Evaluating Corn Stands for Possible Replant”. In it, he uses data from Wiebold that compares planting dates, different yield environments, and stands from 14,000 to 36,000 plants per acre.

The data for an average yield environment shows a population of 18,000 plants per acre that was planted on May 6 has a higher yield potential of 76% than a field replanted on June 5 with a full stand of 30,000 plants per acre (75%), says Luce. In a high-yield environment, more seed is required. A high-yield example shows that a stand of 24,000 plants per acre planted by May 1 would have better yield potential (82%) than replanting on May 31, even with a full stand (77%).

If you do decide to replant, be sure to kill out the previous stand, says MU Extension weed scientist Kevin Bradley. “Herbicide Options for Killing Failed Corn Stands” in the May 2017 Integrated Pest & Crop Management newsletter gives some ideas about how to do it. 

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