Although twin rows work well for some farmers, the verdict’s out on whether you’ll consistently see a yield advantage.

In 2009, Ohio State University corn research plots comparing 8-in. twin rows to 30-in. rows showed no significant difference.

“The twin rows were planted in staggered spacing. And since some hybrids and plant populations may influence corn response to twin rows, we used hybrids with varying maturities (107-, 111- and 112-day) and four plant populations (28,000, 33,000, 38,000 and 43,000 plants/acre),” explains Peter Thomison, Extension agronomist at Ohio State University. “A small but significantly higher yield (approximately 5 bu./acre) occurred when plant populations were increased above 28,000.”

Thomison says the Ohio findings were similar to research in other states where the yield advantage for twin rows was usually less than 3 bu./acre.

At Purdue University, Tony Vyn, Extension cropping systems agronomist, agrees that more producers seem to be interested in twin-row systems for both corn and soybeans than before.

“I think there’s a sense that if you have twin rows and canopy cover is achieved earlier, and if the individual plants are spaced farther apart from each other, it will automatically result in a yield increase,” he says.

But after researching twin rows for two years, Vyn says, “There’s no significant yield gains associated with twin rows in the hybrids we looked at in a population range of 28,000-43,000.”

However, he sometimes sees a little advantage – about 2 bu./acre – with higher plant populations above 40,000 for twins vs. single rows.

“The bigger question is not what’s the row width but rather what’s the optimum density,” Vyn points out. “I believe the impact of plant density on final yield is a much bigger factor than the impact of row width on final yield. Getting plant density right makes more financial sense to pursue than changing from standard 30-in. rows to a twin-row system.” 

Dean Sponheim, a farmer from Nora Springs, IA, and sales rep for Pioneer, says he gets lots of questions from farmers interested in trying twin-row corn. So, his farm was used by Pioneer to cooperate in a large-scale trial looking at plant population and hybrid selection for twin rows.

“We tried nine different hybrids at three different plant population levels last year,” Sponheim says. “Only three showed yield advantages over 30 in. rows, but there wasn’t any correlation as to why. We even planted some at 50,000 seeds/acre and they yielded the same as in 30s.”

The test plots were planted in 30-in. rows with the twin rows 8 in. apart. “The twin rows stood better, but they didn’t yield more,” he says. This year, he’d like to get down to at least 6 in.

“This was our first year and I’m not going to give up on twins,” Sponheim says. “But I’m not going to make a wholesale change to twins like I thought I would. Still, I’m confident that twin rows are where we’re going to have to go.”