Narrow Spacing to Boost Yields

Research shows that planting corn at higher rates in narrow rows can boost yields. But experience shows that this recipe only works under proper conditions. You need to plant the appropriate seeds in nutrient-rich soil to reap the benefit of narrow rows and high populations.

Dan Anderson, Farm Journal Columnist

What has kept the strategy of planting corn in 20" rows or narrower from gaining wide acceptance?

"A 325-lb. NFL lineman wouldn’t make a very good race horse jockey," says Harry Stine, owner of Stine Seed Company near Adel, Iowa. "Just like you can’t interchange athletes between sports, you can’t put corn hybrids bred for 30" rows in narrow rows and expect them to excel."pC9 Narrow and Numerous 4

The impetus to experiment with 20" or narrower rows comes from extensive research at universities across the Corn Belt that indicate corn yields often benefit from higher planting rates. But higher populations crowd plants within the row.

"When intra-row spacing gets to 5" or less it begins to constrain yields," says Kess Berg, Integrated Farming Systems lead corn agronomist with Monsanto Company. "Narrow rows are one way to push plant populations beyond 35,000 without crowding them too much in the row."

For example, at 33,000 plants per acre in 30" rows the plants are 6.3" apart, but in 20" rows their average spacing is 9.4".

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When harvesting 51,000 plants per acre in 12" rows, automatic header height control and autosteer is necessary, says Steve Luther, Stine Seed Company field manager.

Yield push. While Stine acknowledges there are challenges to growing corn at elevated populations, he thinks final stands higher than 45,000 plants per acre are necessary to reach yields of 250 bu. per acre and beyond.

"On the average, farmers harvest 0.3 lb. of dry grain per stalk," Stine says. "In the 1940s, they planted 8,000 plants per acre. Take 0.3 lb. of grain times 8,000 stalks, divided by 56 lb. per bushel and you should yield 43 bu. per acre.

"Today we’re planting corn at around 35,000 population, and still averaging 0.3 lb. of grain per stalk," Stine says. "0.3 lb. of grain times 35,000 plants per acre, divided by 56, figures out to around 187 bu. per acre, which is an average yield across the Midwest."

Using Stine’s formula, it requires 46,500 plants per acre to average 250 bu. per acre at harvest.

Both Stine and Berg emphasize that simply narrowing rows and increasing populations doesn’t guarantee higher yields.

"It’s important to remember that high populations are just part of the picture," Berg says. "In many fields, plant population isn’t the limiting factor. Going with higher populations in narrower rows without optimizing soil fertility and other variables may not increase yields."

Steve Butzen, DuPont Pioneer’s agronomy information manager, says corn yields don’t always increase when rows are narrowed.

"Our data from the previous two decades didn’t show an interaction between row width and hybrid," Butzen says. "The same hybrids that won in 30" rows also won in narrow rows. But things are rapidly changing. If our current or future data begin to show that a specific hybrid is better in 15" or 20" rows than other hybrids in 30" rows, we’ll focus on optimizing that opportunity to achieve higher yields."

Genetics are key. Alpha, Ill., farmer Marion Calmer has grown corn in 15" rows for 15 years. He says history predicts that different seed genetics will be the catalyst that optimizes higher seeding rates.

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Harry Stine, owner of Stine Seeds, vows to never plant another crop in rows wider than 12".

"Think about it," Calmer says. "If you plant the old open-pollinated corn they used to hill-drop in the 1930s in today’s 30" rows at 33,000 plants per acre, the yields would be miserable. You can’t just switch to narrow rows and higher populations and still use the same corn genetics you did in 30" rows."

Stine is convinced that the potential of higher populations planted in narrow rows will only be reached if the hybrid is designed to thrive in that challenging environment.

He admits that after 30 years of research he still hasn’t identified a broad spectrum of hybrids that favor high populations. But he’s developed enough hybrids that benefit from high populations in narrow rows so that in 2012 he planted more than 2,500 acres in 12" rows at 51,000 plants per acre.

Average yields in Stine’s 12" rows were variable due to sketchy summer rains, but ranged from 150 bu. to more than 250 bu. per acre, similar or slightly higher than adjacent fields planted in 30" rows.

"I don’t expect huge, immediate yield gains from planting higher populations in 12" rows. Maybe 5% [better than 30" rows]," Stine says. "The genetics and management practices for higher populations in narrow rows are going to evolve. It won’t happen overnight, and there are places where high populations just won’t work because of poor soil fertility or other limiting factors."

The success of Stine’s first wide-scale use of high corn populations in ultra-narrow rows, planted with two custom-built planters, one manufactured by John Deere/Bauer and the other by Great Plains, encouraged him to add two more custom-built 60'-wide, 12"-row John Deere/Bauer planters to his machinery inventory for 2013.

"I will never plant another acre in anything wider than 12" rows," he vows, "and I predict that just as the majority of farmers made the switch from 40" rows to 30" rows, the majority of farmers will plant higher populations of corn in some sort of narrow rows in the foreseeable future."

Square Seeding

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There’s not a lot of room between 12" rows with 43,000 plants per acre spaced 12" apart.

As planting populations increase, intra-row seeding decreases, creating competition and stress between plants and reducing yields. Marion Calmer, Illinois farmer and guru on growing corn in narrow rows, has done the geometric calculations and offers examples of how different row widths and seeding rates interact to vary intra-row plant spacing.

"Ideally, every corn plant would be exactly the same distance from all its neighbors," Calmer says.  "In 15" rows, corn at 28,000 plants per acre are spaced 15" apart in the row. If you plant 12" rows at 43,000, the plants in the row are 12" apart.

"Even if the intra-row spacing is narrower than the row spacing, "narrow rows still produce less competition between plants," Calmer explains. "At 31,000 plants per acre in 20" rows, the plants are around 10" apart. The bottom line is that higher populations planted in narrow rows give the

individual plants the space they need to maximize yields."