Corn plant population is definitely a component of yield potential for any field of corn. It comes down to simple math in calculating the number of plants that yield a quality ear of corn in each acre of the field, and quality means an ear of respectable size with large kernels.

Fred Below is one of the most outspoken advocates for looking at plant population in fields and focusing on the limits to yield based on the facts of how many kernels of corn can be grown by each plant. Below is a member of the Crop Physiology Laboratory, Department of Crop Science, University of Illinois at Urbana-Champaign.

Higher Corn Population Will Increase YieldBelow includes corn plant population as one of the “seven wonders of corn yield” in presentations he has made around the nation. The other six wonders or influences on yield are weather, nitrogen, hybrid selection, previous crops, tillage and growth regulator use (fungicides).

Yield equals plants per acre times kernels of corn per plant times weight per kernel (Yield = plants/acre  x  kernel/plant  x  weight/kernel).

With this calculation in mind, 250 bushels harvested per acre from a field with only 36,000 plants is almost impossible. He suggests it will require at least 40,000 plants per acre, each receiving sufficient sunlight and good farmer management. It is that assistance with management where ag retailers and crop consultants come into the picture to assist farmers.

To reach the magical 300-bushels per-acre goal for corn production, Below is positive it will take at least 45,000 plant per acre. However, using typical kernels per long ear and good kernel weight, he shows coming up short even at 45,000 plants with 565 kernels per plant and each kernel weighing 260 milligrams.

FARMERS CAN DO BETTER

Using higher corn populations in an economical production system is quite possible for many farmers. In a statement in one of his recent presentations, Below said, “A lot of farmers give up a little yield, I believe, because they are not quite at the populations they need to be. Plant population is an important component of high-yield systems, but it must be managed.”

Below has been experimenting with twin-row, 20-inch and 15-inch width rows. He said, “Twin rows are a challenge but can increase plant population.” He noted that twin-row planting does not respond well in high heat years. Locations where high temperatures don’t occur day after day is where twin-row planting has its most potential.

Not needing to invest in new combines and other pieces of equipment is the advantage of twin-row planting with spacing of about 7 ½-inch twin rows, which also appears to be ideal for nutrient placement and water management.

HYBRID SELECTION KEY

The goal in any population grid that can be developed for a field is to “remove plant-to-plant competition.” Some corn hybrids don’t like to be too crowded, and this is another aspect of management for “high tech” corn production.

“The most important decision that farmers make each year is hybrid selection,” Below said. The importance of the hybrid selection has a lot more to do with yield than just performing well in a particular plant density.  

Additionally, if a plant emerges late and is smaller than those around it from the start, Below’s work shows it will be kept down and crowded out of being a fully productive plant, but if it had emerged at the same time as its neighbors, it would have competed just fine and produced an ear of corn equal to those neighbor plants.

Of course fertility is also a key issue in providing enough fertilizer and having it available to the large number of “race horse” hybrid plants at the right time during their growth progress.

When planting high populations, shoot for the highest yield—again the hybrid selection is key. Below said two major aspects have to be considered in hybrid selection—“those that tolerate high density population and those that utilize nitrogen the best."