|Twin-row planting seems to boost corn yields, compared with 30" rows, but the payoff varies from year to year, says Kevin Koepp.
Corn yields on the farm operated by brothers Kevin and Curtis Koepp, near Belle Plaine, Minn., are gradually climbing—as long as Mother Nature blesses the area with normal rainfall and temperature. No doubt various management factors are involved, but two of them are twin rows and careful planting.
This year marked the brothers' fourth season planting twin-row corn and soybeans—two rows 7½" apart on 30" centers. In corn, their test plots have shown yield increases of 1 bu. to 10 bu. per acre. "The effect on yield varies from year to year," Kevin says. "The past three years, we've averaged 5 bu. more per acre from twin rows.
"I think the yield increase results from planting a higher population (34,000, compared with 32,000 in 30" rows) and more equal spacing of plants," Kevin says. "In twin rows, plants are twice as far apart in the row (12.4", compared with 6"). They are at least 10" from other plants, so they intercept more sunlight."
The additional cost of twin-row corn is fairly modest, Kevin says. In addition to more seed, the brothers apply more pop-up fertilizer at planting—7 gal. per acre of 10-34-0, compared with 6 gal. in 30" rows. "In 30" rows, 7 gal. per acre, applied in the seed furrow, would risk burning the seed," Kevin notes. "But in twin rows, it's like applying only 3½ gal. per acre."
If you apply a soil insecticide at planting, you'll need twice as much because you have twice as many rows, Kevin adds. If you use insect-resistant hybrids, as the Koepps do (except for their 20% refuge), twin rows increase returns from more expensive seed.
Other advantages of twin rows include using the same planter for corn and soybeans and harvesting corn with a standard 30" head, Kevin says.
"With twin-row soybeans, you get most of the yield benefit of narrow rows, but there still is room for air to circulate, which reduces disease," he says. "There is room for your sprayer wheel to run. And they're nicer to combine than drilled beans."
Handle more residue. As they were moving to twin rows, the Koepps were also trying to preserve surface residue cover to protect against soil erosion. Named their conservation district's cooperators of the year in 2005, the brothers follow conservation plans, with measures ranging from filter strips and buffers to residue, nutrient and pest management planning.
Handling the increased volume of residue produced by twin-row corn was a challenge at first. "You get taller, thicker stalks and more leaves," Kevin says. "Our old corn head didn't chop the stalks enough, and our old field cultivator made windrows out of the residue in the spring, so the ground couldn't dry out."
The brothers switched to a Drago chopping corn head. "It sizes residue into 4" chunks, and they start to decompose," Kevin says. After harvest, they run a disk ripper over cornstalks.
The Koepps swapped their old field cultivator for a Case IH Tiger-mate II field cultivator with rolling rear baskets.
To get residue to flow through their planter, the Koepps mounted Yetter Manufacturing 2967 Residue Managers with SharkTooth wheels on the front units and single-wheel residue managers on the rear rank.
The Koepps think they're benefiting from a gentle foot on the accelerator. "We plant at 4.5 to 4.6 mph," Kevin says. "Uniform seed spacing is what it's all about. The trash whippers on the planter help by creating a smooth, uniform seedbed. Anytime the planter unit vibrates, it interferes with uniform spacing of seed."
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