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Corn+Soybean Digest

Spacing Switch?

Old habits die hard. While 30-in. rows may have the highest corn yield in some areas, many southern growers still like 38-40-in. corn spacing to accommodate cotton — even with increased corn acres. It's hard to abandon traditional cultural practices, says Rob Ferguson, Louisiana State University (LSU) agronomist.

“They're hanging on and not shifting,” he says. “The feeling is that cotton will come back.”

He shares the opinion of others in “former” cotton country, which has seen corn acres virtually double the past few years. Switching to 30-in. rows would mean a major shift in equipment originally tailored for lint, not grain production.

But in parts of Texas, corn produced in 30-in. rows out-yields 38-40-in. rows by 5-10%, says Brent Bean, Texas AgriLife Extension agronomist. He notes that unlike other southern growing areas, the Texas Panhandle-High Plains region has long been sold on 30-in. rows.

“The vast majority of our region's growers farm 30-in. corn,” says Bean, adding that virtually all the corn is irrigated in the semi-arid region. “A few are still at 40 and a few have gone to 20-in. narrow rows.

“The yield difference between 30- and 40-in. rows is between 5% and 10%. With our corn yields in the 200-250-bu. range, 10% more corn can easily be 25 bu. more per acre.”

The narrow-row corn can out-yield the 30-in. by 3-4%, says Bean. “However, it's more difficult to scout for insects and cultivation can be difficult if it's needed.”

TEXAS' LARGE PRODUCTION area includes land where cotton still rules due to its ability to produce on much less irrigation water. Some traditional corn growers even added cotton to their rotation the past decade when corn prices were severely depressed. But higher corn prices later brought them back, just as they caused many other southern growers to go the corn route.

Rick Mascagni, another LSU field crop agronomist, has been involved in corn spacing research in northeast Louisiana, where corn averages 160-180 bu./acre under irrigation. “Results have been inconsistent,” he says. “We had cases where 30 in. out-yielded 40 in., but it didn't happen every year. It's hard to get a 30-in. bed large enough for a good planting surface, particularly on the more clay-type soils.”

He says one year's research indicated that 20- and 30-in. corn planted on a flat seedbed had lower yields than corn grown on a 40-in. raised bed. In that year, there was over 20 in. of rain in May and June. “But we still don't expect much change from 40 in. because guys still grow some cotton and have the equipment set for it.

“They also like a corn-cotton rotation due to the advantages it offers in nematode and weed and grass management,” Mascagni says.

Growers considering a switch to 30-in. corn may take a few tips from the University of Wisconsin Extension agronomy department. It suggests that before going to 30-in. rows, growers should consider hybrid selection; machinery suitability for this row width, including silage harvesting equipment if needed; the extra time needed to plant, cultivate and harvest; and the extra herbicide for band application over the row.

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