There are corn hybrids you can plant as thick as you want and still expect consistent results. Then there are hybrids that it’s risky to plant at very high populations.

That’s how Kevin Cavanaugh, director of research for the seed company Beck’s, looks at the issue of how thick to plant hybrids today. “Matching hybrids to the right soil conditions and the production system you’re using is extremely important,” he says. “Work with someone who is knowledgeable about various hybrids, and who knows what to expect when each one is planted under specific sets of conditions.”

Knowing how hybrids react in various environments may be as important or more important than knowing if you’re planting a flex hybrid or a hybrid with more of a determinate ear size. Some hybrids handle stress better than others, and very high plant populations can be a form of stress, Cavanaugh says.

Examples prove point
The 2017 Indiana Prairie Farmer and Purdue University research plot at the Throckmorton research center near Romney, Ind., featured two hybrids planted at five different seeding rates, ranging from 26,000 to 38,000 plants per acre. The goal was to follow up on last year’s study and determine the most economical seeding rate for each hybrid.

Bob Nielsen, Purdue Extension corn specialist, assisted in setting up the plot. He will report on yield results soon. Beck’s donated seed for the plot.

One popular hybrid will flex and still produce well at slightly lower seeding rates than what some other hybrids require, Cavanaugh says. The company’s recommendation is to plant that hybrid about 2,000 seeds per acre lower than some other hybrids, depending upon your seeding rate. For example, if you’re seeding most hybrids at 34,500 seeds per acre, you might plant it at 32,500 seeds per acre.

Daniel Bechman, product support specialist for Beck’s, and Karen Mitchell, Tippecanoe County Extension ag educator, helped take stand counts in the plot before harvest. Bechman examined the same hybrid at different seeding rates. He typically found that ears were longer at the lower seeding rates and shorter at the higher seeding rates. Where higher seeding rates resulted in stress, there may have been more tip-back at the highest seeding rates. Tip-back means kernels formed at pollination but then aborted because the plant wasn’t sure it could fill all the kernels that pollinated, Bechman explains.

HIGH-STRESS ENVIRONMENT: This ear, also of Hybrid A, got caught up in a high-stress environment. Not only was it in a 38,000-seeds-per-acre strip, but it also was closer to a neighbor than normal.

HIGH SEEDING RATE: Here is Hybrid A again. Note the smaller ear next to an average-size ear, more representative of the ear size at the 38,000-seeds-per-acre rate. Stress tends to add inconsistency.

The pictures show that ears of the same hybrid planted at different seeding rates didn’t always look the same. However, Cavanaugh urges caution in evaluating these observations.

“Just because ears were smaller doesn’t necessarily mean that yield was lower,” he says. “Yield is a function of ear size, relating to number of rows per ear and kernels per row, plus kernel depth. But it’s also a function of the number of ears per acre. If you have an extra 6,000 or 8,000 ears per acre, you can still harvest good yield, even if ears are somewhat smaller.” 

Editor’s note: Daniel Bechman is the author’s son.