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Evaluate corn stands now for emergence

Tim Schnakenberg Published on 02 May 2011

Some of the corn planted has been in the ground for a few weeks and the early-planted corn should now be spiking according to Tim Schnakenberg, agronomy specialist, University of Missouri Extension.

“Normally corn should be up and out of the ground within three weeks of planting, but the cooler weather and high moisture levels may cause stands to not emerge evenly,” says Schnakenberg.

“Corn producers should walk their fields and carefully monitor corn emergence this year. Stand counts will help to determine if replanting is necessary.”

The best way to get a stand count is to count the number of emerged plants in 1/1000 of an acre.

According to Schnakenberg, the number of seedlings emerged can be multiplied by 1,000 to get the stand count per acre. For 30-inch rows, count the number of seedlings in 17 feet, 5 inches of row.

For 36-inch rows, count the seedlings in 14 feet, 6 inches. These counts should be done in multiple locations around the field and averaged.

As a general rule, Schnakenberg says to consider replanting if populations are fewer than 16,000 emerged plants per acre for non-irrigated corn or 20,000 for irrigated corn.

“If you need to replant, the date of replanting should be figured in to the decision. In Missouri corn planted past May 10 can result in significantly lower yields,” says Schnakenberg.

A stand that was planted on time but with a thin stand emerged may still be worth salvaging if uniform. However, the decision is more complicated when large gaps exist.

Spot planting these gaps gets very tricky because old plants that survived will act as weeds to the new plants that are established later.

Research has found that spot planting into a poor stand three weeks after the initial planting is not always a good idea due to this competition.

“The yield potential is about ten percent greater if you tear up the field and start over with an even-emerging stand. This decision should be made after factoring date of replanting, cost of establishment, seed and pesticides,” said Schnakenberg.

Schnakenberg also points out some symptoms of some bigger issues in a corn stand that should be evaluated. 

For example, kernels found in the row that are swelled but not swollen could indicate soils that are too cold, too wet or fertilizer that has come in contact with the seed.

Kernels hollowed out may indicate damage from seed corn maggots or wireworms.

“If the sprout is leafed out underground or is twisted, it sometimes is an indication of crusted soil, seed planted too deep, wet soil or herbicide damage."

"Birds will sometimes pull up plants or plants and kernels that are dug up and eaten may be a result of squirrels, mice or raccoons,” said Schnakenberg.

—University of Missouri press release

Tim Schnakenberg 
Agronomy specialist 
University of Missouri