Loose kernels behind the corn head represent more than harvest loss. They can also create a volunteer-corn problem in next year’s soybean crop.
Before changing any settings on your combine, however, Marion Calmer recommends first determining what is causing those kernels to hit the ground.
Calmer, an Illinois farmer and CEO of Calmer Corn Heads, has spent six decades harvesting corn and has worked with both Case IH and John Deere engineering teams. Based on that experience, he says there are three primary causes of butt shelling: genetics, moisture and corn head speed.
Three Possible Causes, One Likely Culprit
“It could be genetics, for one; some corn shells off the cob easier than other corn,” Calmer says. “Second, it could be moisture.”
Moisture can influence how easily the ear separates from the shank, he explains. Early in the day, when corn is wetter, more energy is required to separate the ear, potentially increasing kernel loss from the butt.
The third factor — and the one Calmer says he would investigate first — is corn head speed.
“I think 95% of the time, the problem is going to be the speed at which this ear corn hits the steel,” he says.
Physics at Harvest Speed
Think about what happens to a corn ear as it moves through the corn head, Calmer advises. At slower speeds, the ear moves through the head more gently. As speed increases, so does the force with which the ear contacts the metal components.
“If we run the head real slow, and that ear comes down gently, we don’t see any butt shelling at all because it’s not going to knock those kernels off the bottom of the ear,” Calmer says.
But increase the speed significantly and the result changes.
“If we were to exaggerate this, take an ear of corn and slam it down at 12 miles an hour, then you can see these kernels are going to start to get damaged and they’re going to start to come off the bottom of that ear of corn,” he demonstrates in a recent video.
That makes Calmer’s first adjustment a simple one: “If you’re trying to reduce butt shelling, the first thing I would do is slow the header down so that ear of corn doesn’t smack the stripper plate too hard,” he says.
Don’t Reach for the Wrench
That’s important because Calmer says farmers sometimes respond to butt shelling by immediately tightening the stripper plates. Instead, he recommends diagnosing the source of the loss before making an adjustment.
Penn State Extension’s guidance on minimizing corn harvest losses also emphasizes diagnosing the source of kernel loss before changing combine settings.
It says to start your evaluation process by stopping the combine and inspecting the ground behind the combine. If loose kernels are concentrated in the row, pick up several ears and examine the butt end. Missing kernels there are a telltale sign of butt shelling.
A Methodical Approach to Adjustments
If kernels are being removed at the corn head, check deck-plate spacing and corn head speed. Penn State notes that deck plates that are too wide can allow the ear butt to contact the stalk rolls and knock kernels loose. Dry, brittle or small stalks can make the problem worse.
Then make one adjustment at a time. Start with the corn head, adjust deck-plate spacing for stalk size and field conditions.
Harvest a short distance and inspect the ground again to determine whether kernel loss has improved. That approach helps identify the source of the loss before multiple settings are changed at once.
Lost Kernels can Become Next Year’s Problem
The concern with corn butt shelling goes beyond what is left behind in the field at harvest.
Every kernel lost at the corn head is grain that never reaches the bin. In a corn-soybean rotation, those kernels often become volunteer plants the following year.
A 2016 University of Nebraska study by agronomic researchers Chahal and Jhala found that one volunteer corn plant per square meter reduced soybean yield by 22% under the study conditions.
Volunteer corn can be particularly challenging to control because most modern corn hybrids contain multiple herbicide-resistance traits, adds Penn State. Controlling volunteer corn in soybeans can require additional herbicide applications, adding another layer of expense.
Lessons from Six Decades in the Cab
Calmer recalls that when he was young, corn was picked by ear, with ear separation occurring on the picker rolls. While modern corn heads use stripper plates, the goal remains the same: move the ear through the head without knocking kernels off.
“I’ve been harvesting for 60 years,” Calmer says. “My grandpa told me that if we don’t butt shell the ear, then we don’t have to worry about cleaning it up.”
The bottom line, he says: When kernels show up behind the corn head, resist the urge to immediately tighten stripper plates. Stop the combine, inspect the ears and loose kernels to confirm butt shelling, then consider corn head speed. Those few minutes of diagnosis could save bushels this fall and prevent a volunteer-corn headache in next year’s beans.
Watch Calmer’s video and hear all his recommendations at the link below:
