Top Causes for Mechanical Corn Yield Loss

No corn harvest season is ever perfect.

It’s impossible to get every kernel of corn out of every field. But, by identifying the causes for mechanical yield loss, you can minimize the bushels you leave in the field and help preserve corn revenue when you harvest your crop this fall.

Harvest equipment can have a lot to do with how much yield loss you experience. Being attentive to both equipment and field conditions is critical in minimizing yield loss. Research shows during harvest, 60% of yield loss typically occurs at the corn head, according to Iowa State University Extension agricultural engineer Mark Hanna.

“The challenge is as farmers go from one harvest season to the next, one field to the next and one acre to the next, things are not always normal. Harvest conditions change based on your weather and more,” says Dragotec USA president and Fenton, Iowa, farmer Dennis Bollig. “It only takes two kernels/square foot to equal a bushel/acre. With 600+ kernels on an average-sized ear, that can add up to some real bushels quickly.”

There are two primary ways yield loss occurs mechanically: Ear and kernel loss. Corn moisture can dictate how much of both you experience; the wetter the corn, the more likely you are to experience ear loss, while drier conditions foster kernel loss.

“When the corn might be wetter, you get more ear bounce,” Bollig says. “When you have 25% moisture corn, the kernels are held tightly onto that cob, so when the energy of that stalk roller hits that deck plate and the corn is pulled down fast, you get a pretty dramatic ear bounce.”

Ear loss

Other types of ear loss causes include:

- Ears bouncing forward with the wrong corn head angle.

- Higher knife roller speeds: Though it can aid in sizing residue for better breakdown in the field, faster knife rollers can lead to more ear bounce out of the corn head.

- Losing ears over the side of the corn head.

- Pulling ears through misadjusted corn head deck plates.

- Failing to gather ears from down corn leaning away from row units.

Kernel loss

Even some of the smallest gaps in and between components like corn head deck plates can lead to kernel loss of up to four bushels/acre, research shows. Adds Bollig: “We know that every 1/8 inch misadjustment can mean several bushels/acre depending on the corn you’re harvesting.

Reasons for kernel loss include:

- Butt-shelling: Kernels separating from ears because of the impact of a dry ear hitting the corn head deck plate. Dry corn shells five times more than wet corn, making dry fields more susceptible to yield loss from butt-shelling.

- Hydraulic deck plate gap variability: Without recalibration, the gaps between hydraulic deck plates can become variable and inconsistent, allowing kernels to slip through or bounce out of the to the ground.

Bollig adds components like automatic self-adjusting deck plates and systems like the Drago GT corn head’s QuadSuspension help better account for many mechanical yield loss causes, helping get more corn out of the field and ultimately sustaining stronger profits.

“That corn left on the ground represents your profit,” he says. “Any corn left in the field comes out of the farmer’s bottom line.”

If you’d like to learn more about how a Drago GT or Series II corn head can help minimize yield loss, contact your local service technician or dealership. For more information on Dragotec USA corn heads, go online to