Top 5 causes for corn yield variability at planting time

Sponsored by Dragotec USA, Inc.

Even before planting, corn faces yield loss potential. Variability in growing conditions can cause it early on in the growing season.

Starting from day one, a myriad of factors exert influence on every corn kernel planted, causing variability in conditions that can lead to a range of potential yield loss. As planting season nears, it’s critical to make adjustments to account for these causes of variability in corn yield potential. Some may be visible and clear during the growing season, while others may only manifest themselves as yield loss when the combine runs this fall.

“There are so many things that cause stalk size variability in a corn field,” says Dragotec USA president and Fenton, Iowa, farmer Dennis Bollig. “But, with so many causes for that variability, stalk and ear size may change a lot across different microenvironments in every acre.”

Variability factors

Here are a few conditions to stay on top of as you begin planting this spring. Doing so can help minimize potential yield loss when you harvest your crop this fall.

1) Soil type

Plant variability can happen in a matter of feet in a corn field. And, that variability at harvest actually starts well before the seeds are sown in the spring. Soil type, including factors like organic matter, soil pH and water retention, is a major driver for a crop that may show inconsistent results in the field at harvest.

“When you move across the field from one soil type to another, one may grow bigger plants with stronger stalks than the next,” Bollig says. “Soil type variability doesn’t happen in straight lines, and I have fields that may have anywhere between five and 20 soil types. That can cause major plant variability.”

2) Crop residue

How much crop residue present in your fields in the spring depends a lot on your crop management system. And, when it comes to being a cause for crop variability, it’s about a lot more than just the amount of residue left in the field. Where it is in the field at and after planting can have a big effect on how much variability it can create.

“If corn residue gets into the furrow, some seeds may have residue right next to them in the ground, while others may not. That will affect soil temperature, and you will see variety in plant sizes,” Bollig says. “When you’re planting multiple varieties, that can cause variability in the residue size and breakdown, and that can affect how different plants emerge and grow, too.”

3) Soil drainage

This is one of the most visibly noticeable causes for plant variability throughout the growing season. How well the soil drains excessive moisture goes a long way to how variability earlier on in the growing season manifests itself as yield loss at harvest. Variability caused by inconsistent soil drainage across a field is complicated by plant populations and hybrids.

“You can drive down a road and you’ll see areas of some fields where the corn is taller and greener, and areas where it’s shorter and yellower. That’s because of excess moisture,” Bollig says. “Drainage is not consistent across any field.”

4) Topography

Though weather — namely precipitation, frost and wind — are major drivers for in-season crop variability, don’t neglect accounting for topography and the layout, slope and general surface variation in your fields. That’s especially true when assessing specifically how those weather variables affect your crop potential.

“Sometimes a frost isn’t uniform across a field, and topography and soil types can create huge amounts of variability among corn plants,” Bollig says. “With wind, some parts of the field have better protection than others, and you will have bigger plants in those areas that don’t fight wind as much.”

5) When and how much you plant

Planting dates and plant populations are major factors when it comes to overall crop variability. Earlier planting makes seedlings more susceptible to early frost damage, while pushing plant populations higher can sometimes cause crop stress during the growing season.

“Farmers are pushing plant populations higher, so when you have environmental stressors, they will be magnified. One issue is you may have a lot of smaller ears, and with smaller ears, you’re more susceptible to yield loss through the corn head,” Bollig says. “We’re growing more ears per acre, but as you move through fields with different soil types and weather patterns, we are creating a huge amount of variability.”

Counteracting and minimizing variability

Though some variability is inevitable, farmers can take steps to minimize its influence on corn yield loss. Accounting for soil pH and type through soil testing and nutrient management can help create more consistent fertility. Soil drainage can be improved by adding drainage tile.

Yet, some variability will remain by the growing season’s end, making it critical to best match harvest operations for the conditions you’ll face, thereby minimizing yield loss at harvest. Though it may be far from farmers’ minds during planting season, thinking about how conditions can best match harvest equipment — especially the corn head — is important even this early in the year.

“Having a corn head with self-adjusting deck plates is so important. You can adjust the deck plates manually on every corn head out there, but with all the potential variability in every field, stalk and ear sizes can change numerous times in every acre, sometimes even within a few square feet,” Bollig says. “The goal is to grow more corn more efficiently, and sometimes we inadvertently create variables upon variables. But, we know that the best place for your deck plates is up against the stalks. That’s going to minimize your yield loss.”

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 Drago dealer. For more information on Drago corn heads, go online to