Last year produced red-hot yields for Mike Rosenbohm, who farms near Graham in northwestern Missouri. His average corn yields were up 20% from his long-term average, with yields ranging from 180-225 bushels per acre. So when a narrow-row, high-population test field had a corn yield bump of 30% or more compared to nearby corn planted in 30-inch rows, he signed a contract to purchase a narrow-row planter.

The John Deere twin-row, 20-inch planter (only offered by Stine) is configured with staggered row units (twin rows are 8 inches apart, with 12 inches between twin-row pairs). With an average row spacing of 10 inches, seeds are spaced every 12.6 inches at a 50,000 plant population. That compares to every 6 inches for a 35,000 plant population in 30-inch rows.

“Weighed checks average 274 bushels per acre. The field average was about 250,” he says. “In places, the yield monitor was running 300 to 330 on ground that normally runs about 160 bushels per acre.

“From what I saw this year, even with the good yields we had with 30-inch corn, this is much better,” says Rosenbohm, who conducted the field test in conjunction with Andrew Lance, his local Stine Seed dealer. “Comparing this system to my normal program, with extra seed, fertility and transportation costs, I needed a 10% yield increase to break even.”

In Paton, Iowa, 175 miles north, Jim Doran came to different conclusion after a similar narrow-row, high-population Stine corn trial showed more modest results on his farm.

“I can see a lot of positives to this system, but I want to see more research before I put an investment in this,” says Doran, who notes that hail damage compromised yield comparisons. “As a whole, I would say the high-population corn outyielded the 30-inch corn. It at least covered the extra costs for seed and fertilizer.”

Early canopy, erosion protection

Narrow-row, high-population corn (38,000 to 50,000 seeds per acre, depending on soil type) had several side benefits as well, such as improved weed and erosion control and lower temperatures within the crop canopy, Rosenbohm says.

The early canopy closure in his 10-inch rows created stellar weed control for his preemergence herbicide-only program, even though moisture conditions favored ongoing weed flushes. “When the crop was about boot-top high, the ground was covered,” he says. “It looked like wheat. Weed control was quite a bit better than 30-inch corn, even with a single herbicide pass.”

Later on, temperatures within the canopy were 5 to 10 degrees cooler on sunny days than readings in 30-inch corn. This could boost crop development in extreme heat, plus reduce crop transpiration and soil moisture losses, Rosenbohm says.

Improved erosion control was an especially pleasant surprise. Rosenbohm’s main test field, which includes 5% to 9% slopes, received multiple 4- to 7-inch rains over several hours. While another high-population test on low ground was knocked down, “There was very little soil loss on the hills because the ground was covered,” he says.

He boosted nitrogen (N) rates to 225 pounds from his normal 180-pound rate. Otherwise, management was the same. Frequent scouting showed no need for fungicide, despite the tighter canopy and moist field conditions.

Narrow-row corn presented further surprises. Rosenbohm discovered the ease of scouting and checking planter performance with closer spacings. Harvesting with a 20-inch head, which grabbed two 10-inch rows at a time, was a revelation.

 “It’s like cutting soybeans,” he says. “Harvesting at 45 or 90 degrees to the row works best. Running across the rows is strange at first, but with autosteer it isn’t bad. You can take end rows and the rest of the field in the same pass.”

Rosenbohm opted to replace a 24-row planter with a Great Plains central fill, 40-foot planter configured for his 10-inch row under a special plan through Stine Seed, which normally offers a John Deere planter program (see sidebar). Under the program, he pays 10% of the list price the first year, plus specified minimum seed purchases in 2015–16. If he rolls the agreement into the second year, he will owe another 23%. After that, he will own the planter free and clear.

 “I want to keep experimenting with high populations and narrow rows, and with Stine paying for two-thirds of the planter, that makes it possible,” he says. “With our terraces, a 40-foot width works better. If this doesn’t work out after next year and I turn it back, I am basically leasing the planter.”

Tough 220-acre test

For Jim Doran in Iowa, 2014 was not the best year to test a new cropping practice. After Stine Seed planted 220 of his acres in twin-row, 20-inch corn, the rainfall hardly stopped.

 “Early on, the twin-row corn looked superb,” Doran says. “As the water kept coming, plus hail, it kept pulling back. I have never experienced soils that were completely saturated from spring into July and August.”

Test fields were planted at 55,000 seeds per acre, compared to 34,000 to 36,000 seeding rates in comparison 30-inch rows. The two fields, which were planted following soybeans, were fertilized with 150 pounds of N in the fall. He applied another 100 pounds as 32% liquid N in the spring on the tests, which also received fungicide. Weed control was excellent.

 “Even though I applied plenty of nitrogen, it might not have been available to the plant with all that moisture,” he says.

The best test field yield was 215 to 220 bushels per acre, not counting a 20% hail adjustment. “Without hail and extra moisture, it’s hard to know just how well this corn would have done,” Droan says.

Long-term, though, he believes that high-population, narrow-row planting systems show promise. “We are pushing the max on standard hybrids right now,” he says.

Moisture-saturated soils challenged tests in 2014

After two years of tests with custom-built, 12-inch planters and corn heads, Stine Seed reconfigured its high-population, narrow-row planting system with twin-row, 20-inch planter and harvest setups on 10,000 acres over 105 farms in Iowa, Indiana and Missouri in 2014.

It was the biggest test yet of its kind for Stine Seed, the only U.S. seed company to promote the planting system as a breakthrough to higher yields. In 2012 and 2013 field trials, Stine’s hybrids bred for high-population environments – planted at populations as high as 55,000 seeds per acre – outperformed standard varieties in 30-inch rows.

The 8-inch, twin-row John Deere planters performed well. However, in 2014’s wet, fickle growing season, there was no significant yield difference between high-population and non-high-population corn, except where nitrogen was not limiting or moisture was not excessive.

 “A lot of our guys are happy because our genetics performed well overall in 2014,” says Myron Stine, vice president of Stine Seed. “But they were disappointed because when they did ear checks, the high population was showing an 80- to 100-bushel yield difference. The crop just ran out of gas.”

Regardless, the company remains convinced that planting higher populations of hybrids bred especially for that environment will outperform standard hybrids in 30-inch rows. “Where we had adequate nitrogen, high populations were 20 to 30 bushels per acre better,” says Stine. “Over a five-year average, with our genetics planted at higher populations, you are going to be ahead. Normally, across the Midwest, water is the limiting factor. That’s where our system excels.”

More acres in 2015

Stine Seed also unveiled a subsidized planter purchase program to expand commercial adoption of its high-population system in 2015. As the sole distributor, the company offers John Deere twin-row, 20-inch planters at a 67% discount over list price with qualifying seed purchases.

“Initially, we had a goal of moving 100 planters,” Stine says. “We now think we will be at 120 to 130 planters.”

Under the program, growers pay 10% down the first year, plus make a two-year seed purchase commitment. After the first year, they can return the planter or pay an additional 23% of the list price to buy it outright. Seed purchase requirements depend on planter size. A 40-foot planter equals a 1,200 bag-commitment over two years.

Stine says the twin-row planter performed well in 2014. Because of increased spacing between seeds with the higher row density, operators were able to run planters at about 7.5 mph without yield-robbing singulation issues. “Your meters have a lot more leeway for error without affecting yield when you have 12 to 14 inches between seeds,” he says.

Planters were set up on tramlines for in-season application flexibility by blocking row units adjacent to tractor tires.

Harvesting paired rows with a 20-inch corn head also worked well. “We learned that you can harvest twin-20 rows diagonally with a 20-inch head and lose practically no grain,” Stine says.