Higher corn populations may be the way of the future, but seed companies are finding yield and economic benefits from high populations are both hybrid- and field-specific.

Myron Stine, president of Stine Seed Company, said his company began to see benefits in hybrids that performed well at high populations in the early 1990s. Over time, they started to identify the genetics responsible and developed a high-population growing system matched with specific genetics.

Genetics are fluid, but it takes a long time to change those, Stine said. We view (high-population corn) as a constantly evolving technology (and) management practice.

Honing in on higher populations

Stine said the number of growers in 2016 who saw a difference from higher population corn was fewer than in 2015, but those who did notice a difference saw a more dramatic improvement.

Like other management practices, farmers who use higher populations expect better yields on average across multiple years just as varying benefits are expected from fungicide or split-season nitrogen applications because of variable growing season conditions.

Stine said that in 2016 some high-population plantings had nitrogen left over, while the high-population fields with the biggest yield gains used up the available nitrogen.

The company developed a twin 20-inch-row planting system with John Deere and Great Plains. The twin rows can be harvested with a 20-inch corn header while halving the row spacing width. A twin 30-inch-row system is also possible.

This system is also being used with variable rate technology. Growers are varying populations from 30,000 to 45,000 seeds per acre and changing hybrid selection as they move from less productive to more productive ground.

Pairing populations and hybrids

Paul Carter, DuPont Pioneer senior agronomy sciences manager, said all Pioneer hybrids are tested at 20 to 30 locations over several years, plus hundreds of on-farm trials. Planting populations in some of these tests range from 18,000 to 50,000 seeds per acre on 30-inch rows.

In general, Pioneer has found the seeding rate required to maximize yield increases as yield level increases, Carter said.

The economic optimum seeding rate varies from about 30,000 seeds/acre for locations yielding 150 bu./acre to over 37,000 seeds/acre for yields of 240 bu./acre. Average responses vary by hybrid and local situations.

Brad Van Kooten, DuPont Pioneer senior marketing manager, said in studies looking at high seeding rates in 15-inch rows, they found about 80 percent of the germplasm worked well with 30-inch-row performance 20 percent responded differently. Of the total, 10 percent performed better in narrow row, high-population environments over a period of at least three years.

The benefits from these top-performing, high-population hybrids are incremental, Van Kooten said. While statistically better, they were not make or break differences.

Producers should review soil fertility levels to make sure they match their higher production goals, he said.

Pioneer also found a correlation between higher seeding rate advantages and shorter maturity corn.

Location is likely an important factor as higher planting densities may be better able to take advantage of a shorter growing season, Van Kooten explained.

Carter said that over the past 50 years, improved corn genetics have led to a gain of around 2 bushels per acre per year.

A lot of that gain has come from developing hybrids that can withstand the stress of plant to plant competition, he said.

Its important for growers to keep up with this gain, but the additional population required may be near an additional 250 plants per acre per year, he said.

So theres been a steady, a linear increase. We havent seen a step change, he said.

Van Kooten said theyve learned that the highest yielding genetics may not always benefit from higher populations. Population should be a hybrid-by-hybrid decision.

To find the sweet spot for each hybrid, Pioneer has a number of tools, including a Planting Rate Estimator app. Local seed reps likely are the best resource for farmers, Van Kooten said.

Understanding high populations

Becks Hybrids Practical Farm Research Agronomist Alexandra Knight said theyve seen a trend of high population seeding rate success in highly productive soils with high organic matter.

Knight said Becks participated in a multi-hybrid planting study from 2012 to 2015, testing offensive and defensive hybrids and corresponding seeding rates based on yield map history. It found a 7 bushel per acre benefit in corn.

Their Iowa 2016 High Yield Attempt PFR study a moonshot of sorts for highest yield also showed a yield advantage with a higher seeding rate.

Knight said some of the factors that seem to play a role in making a hybrid that performs best at high populations include uniform emergence and consistency of ear fill. Precise nitrogen placement, both timing and location, has also been key in high-yield attempts.

In 2017, PFR research will include testing hybrids at planting rates from 30,000 to 42,000, Knight said.

As they continue to develop their high population corn system, Stine said they are finding a number of traits are responsible for making a hybrid that performs well at high populations.

Generally, we are seeing shorter plant types with more upright leaves, he said.

On some high-population hybrids, they are beginning to see tassels below top leaves of the plant, he added.

Earlier flowering is also common observation with successful early season hybrids, Stine said.

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Genetics key with high corn populations - Illinois Farmer Today