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Corn+Soybean Digest

Narrow Rows Broaden Yields

With higher yields and fewer weeds, narrow-row corn is paving the way to wider returns for a pair of Kansas growers.

Gary Wilbur and Roger Cooley, both of Leoti, KS, grow much of their corn for silage, which is sold to regional feedyards. They are also among many growers across the Corn Belt who have switched to 15- or 20-in. rows.

Wilbur, who has grown irrigated corn and wheat in west central Kansas for more than 35 years, began his switch to 15-in. corn in the late 1990s.

“I wanted to get a canopy established quickly to help decrease my dependence on cultivation and herbicides,” he says, noting that he plants corn into no-till wheat stubble. “I tried a half-and-half test with 15- and 30-in. row corn to be cut for silage. The narrow-row corn yielded four more tons per acre.”

His 15-in. corn yield was 33 tons, which would equal about 265 bu./acre if harvested for grain. The 30-in. rows produced 29 tons, which converts to about 230 bu.

“Those additional yields are from the same plant population as 30-in. rows — 30,000 seeds/acre,” says Wilbur. The narrow rows' wide seed spacing and staggered planting pattern gave plants more space for development, he says.

For 30-in. rows, he plants one seed every 6 in. For 15-in. rows, seeds are planted about 1 ft. apart. A 31-row John Deere MaxEmerge variable-rate planter is used that can also be converted to a 16-row planter for 30-in. rows.

The planter is similar to one Cooley uses on his farm and in his custom farming operation. Staggered planter boxes plant seed in a zigzag pattern.

“No plants stand side-by-side with plants in the adjacent row,” says Wilbur. “There is less stress on the plants and that enables plants to grow easier and perform better.”

Cooley likes that 15-in. corn establishes a canopy faster. “We use about 25% less herbicide because of the earlier canopy,” he says. “If the canopy takes care of the weeds, you don't need such a long residual (from herbicides).”

Cooley grows dryland corn. He plants about 18,000 seeds/acre and enjoys strong yields that outperform corn grown in 30-in. rows.

Chris Boerboom is a University of Wisconsin weed scientist who has observed numerous field tests of narrow-row corn in Wisconsin and other states. He says growers can benefit from increasing their seeding rate with narrow rows.

“Typically, on a medium-textured soil, we shoot for a harvest population of 30,000 plants on 30-in. rows,” Boerboom says. “If you decrease row spacing to 20 or 15 in. and increase plant populations to 35,000, that combination really helps increase shading and reduces weeds.

“In general, it seems the potential for a yield increase in narrow rows increases the farther you go north,” he adds. “In the northern base, there may be a more consistent payoff for narrow row than in the southern (Corn Belt).”

Kurt Thelen, crop and soils specialist at Michigan State University in East Lansing, says that while silage yields are usually substantially stronger for narrow-row corn, grain yields using the same plant populations are not that much better.

“We see about a 4% increase in yields when going from 30-in. to 15-in. row spacing,” he says. “In one study, we compared five different plant populations across the board. The 4% range was consistent for all populations.

“But if you bumped up populations, you would expect to see a yield increase,” he says. “And as genetics continue to improve and the optimum plant population is pushed higher, you could also expect to see stronger yields with narrow-row corn.”

One concern with increasing plant populations is stalk strength and lodging. “That's something growers have to balance when increasing their plant populations,” Boerboom says.

Another drawback to narrow-row corn is the inability to cultivate. Although the crop can better compete with weeds in narrow rows, he adds, “there isn't much evidence that narrow rows can completely replace cultivation.

“Until more consistent and favorable results exist for weed suppression with narrow-row corn, it seems wise to either be prepared with a narrow-row cultivator or to repeat herbicide applications in years when initial herbicide treatments don't give adequate control,” he says.

Wilbur doesn't have problems with the cultivation dilemma. “You can't cultivate, but there is much less need to,” he says. “We either apply Bicep or Dual and receive pretty good protection against weeds until the canopy is developed.”

Finding the right harvesting equipment might also be tricky. Corn heads must be narrow to help prevent grain losses at harvest. For silage production, Cooley and Wilbur count on a Deere 6950 cutter equipped with a Kemper head that can handle rows of virtually any width.

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