Although it brought above-average corn yields for some growers, the 2016 cropping season was a bizarre one for many in Nebraska — most notably, the wide temperature swings in the south-central part of the state in early to midsummer. Extreme weather isn't out of the ordinary for corn growers on the Plains, but last year saw something else that added to the mix: widespread ear deformation issues, including dumbbell-shaped ears, multiple ears per node and short ear husks. These abnormal ears were accompanied by varying ear heights and ear nodes of corn plants within the same row.

While it's not yet known what exactly caused these issues to occur, or what the overall yield impact was, Justin McMechan, Nebraska Extension crops specialist; Roger Elmore, Extension cropping systems agronomist; and a team of researchers at UNL are studying the conditions at play that may have led to these issues. During the 2016 growing season, McMechan and Elmore collected samples from 16 fields in south-central Nebraska and one field in eastern Iowa. Moving forward, they plan to study the samples to identify contributing factors.

"Right now, we're really just trying to get a handle on how these ear formation issues might relate to corn growth and development that might provide some insight into why this happened," McMechan says.

Factors at play
These growth and development factors include node height, husk length, ear node and ear height. While it's not known for certain, a lower ear node height may be an indication of the loss of the primary ear. Previous research has indicated that environmental conditions could cause a loss of the primary ear, causing the plant to initiate a secondary ear at lower node through plant hormones.

"The plant wants to survive, so it's putting its resources toward the secondary ear, which doesn't have as much hormonal apical dominance as the primary ear," explains Elmore. "Looking at Justin's new data from the locations where data collection and summary is complete, it looks like ear height was lower on most of these odd types of ears, which supports the hypothesis that we lost our primary ear node — although that may not be the case."

Then there's the question of what caused these deformity issues. Last year's bizarre weather events may have been a factor for south-central Nebraska. With a mix of below- and above-normal temperatures in June, and cold temperatures and wind in early July, it's hard to say exactly which of these conditions, or the combination itself, played a role. Likewise, eastern Iowa also experienced a cold snap in early June.

"We started off wet in May, and then we got really dry in June. This may have left some corn plants with really shallow root systems, which could have affected water stress later on," says McMechan. "It's safe to say that we had a lot of underlying stress events in 2016."

And Elmore says some hybrids may be more susceptible than others. "These are typically racehorse hybrids that are cutting-edge, top-of-the-line performers. What happens when you put a quarter horse on a mile-long track? I'm not a horse racer, but I don't think you want a quarter horse running a mile track," Elmore says. "These are cutting-edge hybrids, and when you're sitting on the cutting edge, things need to be lined up pretty well. Otherwise, they're going to fall off the edge."

Putting the pieces together
So what factors or combination of factors are responsible for these symptoms? At this point, it's hard to say. "That's what we're hoping to figure out. It could be different environmental triggers at different locations that resulted in similar symptomology. It's a big puzzle," Elmore says, adding that the puzzle "could have 10,000 pieces."

The next step is to sort through this giant data set from the sampled fields and, hopefully, identify a possible causal relationship between environmental conditions and ear formation issues experienced in those fields.

McMechan and Elmore plan to recruit a graduate student who can help with the analysis, and a visiting scientist from Henan Agricultural University in Zhengzhou, China, is also joining them to help analyze these documented cases. By plotting out the specific weather data for each location, they hope to identify the stress triggers that resulted in these symptoms. Then they'll simulate these symptoms in the greenhouse, including evaluating different hybrids for these conditions. "Once we figure it out, we can help ensure it doesn't happen again," Elmore says.

However, McMechan notes, this kind of in-depth research takes time.

"If you're expecting an answer for the coming season, it'll be nearly impossible for us to come up with something solid. It's actually going to take a couple years," he says. "We're in Step 1 in what are probably three to four steps over the next couple years in order to gain a full understanding of this situation. It's also possible we may find this situation is such an anomaly that we may not see this again. Roger Elmore has worked in corn for more than 35 years and has not seen all of these symptoms come together at the same time before."

Other researchers involved in this project are Jenny Rees, Extension educator; Tom Hoegemeyer, adjunct professor of practice at UNL's Department of Agronomy and Horticulture; Joe Keaschall, professor of practice in the Department of Agronomy and Horticulture; and Tamra Jackson-Ziems, Extension plant pathologist.

This research is ongoing and any growers that have information from their experience to share can contact Elmore at [email protected] and McMechan at [email protected].