If your corn emerged unevenly this year — and whose didn’t, with the dry soils, crusting and frost that occurred — you might expect to see a 5- to 6-bushel-per-acre yield loss.

That’s based on a 200-bushel-per-acre crop, and if 10% of your plants emerged anywhere from five to 17 days later than the rest of the field.

If you had 10% skips, you could expect a 16-bushel yield loss on a 200-bushel-per-acre field.

EAR IMPACT: This picture shows corn ear size as affected by date of emergence and by being next to a skip. (Photo: Lindsey Novak)

The numbers come from surveys done in 2013 and 2014 by Lindsey Novak, Bismarck State College assistant professor of agriculture, technology and natural resources; and North Dakota State University Extension specialists. They counted the number of skips, doubles and late-emerging plants, and measured the impact each had on the size of the ears on adjacent plants. Skips, of course, produced no ears — but ears next to the skips were bigger.

“Corn is one of the most sensitive crops when it comes to plant population and uniformity in timing of emergence,” says Joel Ransom, NDSU Extension agronomist. “Partly, this can be explained by the small number of seeds that are planted relative to other crops (30,000 for corn vs. 1.5 million for wheat), so a missing plant has a proportionally greater impact. Additionally, corn is a poor competitor during early development, so a late-emerging plant rarely will achieve its genetic potential, and in the worst case will not produce an ear but will compete for light, water and nutrients with neighboring plants. It becomes a weed.”

The most common problem the research saw was plants emerging late (five to seven days after the first flush). In the most variable rows monitored, up to 25% of the corn plants were found to be in this category in 2013. Doubles were rare (less than 2%), while skips or plants that failed to emerge averaged about 4.4% of the potential stand. About 4% of the plants were extra-late emergers (10 to 17 days after the first flush).

“What is most surprising is the increased percentage of plants that actually emerge late, even when the stand looks good at first glance, and the environmental conditions seem satisfactory,” Novak says. “A producer may take a quick look, either by truck or ATV, and assume the stand looks great. This even happened with the other observers and me when plotting out the sites. But, a closer look, with stand counts taken over time, revealed that up to 25% of the stand [was] five to seven days late (or approximately two leaves behind). These late-emergers do have a significant impact on yield.”

There was some good news in the study. Doubles actually increased yields by 6-bushel-per-acre rows that were monitored. The ears of the double plants were smaller than a single plant, but the combined yield was greater than the single. There were a limited number of doubles counted in the study, though.