Double Take on Twins

March 11, 2010 04:26 AM

Kevin Wood doesn't care if you call him narrow-minded. The Raymond, Ill., farmer is looking for a way to eke every last corn bushel out of his land. When a 2008 twin-row corn plot showed an amazing 30-bu. yield bump, he wanted a closer look at the concept.

His curiosity mirrors that of the Farm Journal Test Plots team, which first tested twin rows in 1999. The momentum for the practice of planting two rows 7" apart on 30" centers has built in the past few years as more corn contest yield winners use twin rows to take home honors.

"By 2006, twin rows had advanced from a niche practice used primarily by vegetable growers to a mainstream option for corn growers,” says Ken Ferrie, Farm Journal Field Agronomist, who oversaw our replicated twin-row plots. "That was the year when some of the winners in the National Corn Growers Association Yield Contest used twins to achieve their big yields.”

Twin rows work well for producers who have maxed out planting populations and yield potential in 30" rows, Ferrie notes. The narrow row spacing can also aid in water management.

Yield quest. To evaluate twin rows for himself, Wood and his son, Brian, worked with Channel Bio, a seed corn subsidiary of Monsanto Company, to launch a twin-row test. Other farmers soon jumped on board and the effort ultimately covered 7,900 acres in
Illinois, Arkansas and Missouri.

"Our goal is to find a way to push populations beyond the 36,000 to 37,000 plants per acre typical of 30" rows,” Brian explains. "We want an ear on each plant about the size of a soda can.”

As you might guess, it turned out to be a tough season for any kind of test. The wet spring led to late planting and that was further complicated by the sharing of twin-row planters to establish the test strips.

Yield results for the first-year plots at Wood Farms ranged from an 11-bu. yield advantage to an 11-bu. yield loss. Father and son saw the best results with more determinate-type hybrids.

Will Mullenix, Channel Bio technical sales manager and agronomist, says when plot results were tallied this year, there was only a slight yield benefit to twin rows across all trials. Channel Bio farmer–cooperators were encouraged to compare twin rows with 40,000 plants per acre to 30" rows with 36,000 plants per acre while keeping other inputs equivalent.

"We believe some configuration of narrow-row corn holds promise. We're trying to help our customers maximize harvestable ear counts across the variable yield environments on their farms,” Mullenix says.

"Twin rows help minimize interplant competition, especially when final stands are above 36,000 plants per acre,” he adds.

In 30" rows, the field area available for rooting decreases as populations increase due to interplant competition. With twin rows, the root area increases as populations increase because plants are spread out over more area.

Family ties. AgriGold agronomy manager Mike Kavanaugh notes that years with above-average rainfall lessen stress during the growing season and can minimize the benefit of narrow-row corn. Even so, AgriGold's 2009 twin-row study shows a 4.9-bu. advantage compared with 30" rows when all hybrids and populations are considered.

"The trendline for twin rows suggests grain yield continues to increase up to 43,000 plants per acre,” Kavanaugh explains. "The trendline for 30" row systems begins to plateau around 34,000 plants per acre” based on the company's 2009 first-year data.

The AgriGold agronomy team planted 37 research plots across the Corn Belt, using five hybrids at populations ranging from 28,000 to 43,000 plants per acre. They compared each population in 30" rows to twin rows. The tests were planted in commercial fields using each farmer's individual production practices.

Kavanaugh says the results showed agronomic differences, such as larger stalk diameters that could lead to less lodging. "Greater stalk diameter is a direct result of reduced competition and larger root systems,” he notes.

Ear heights averaged 1" higher in twin rows compared with 30" rows as populations exceeded 33,000 plants per acre. Twin-row plant heights averaged 1.5" taller than all populations compared with 30" rows.


The Impact of Narrow Rows
Charlene Finck, Farm Journal Editor
In a decade of studying narrow-row corn in twin and 20" rows in replicated plots, the Farm Journal Test Plots have shown that narrow rows out yield 30" rows by as much as 22 bu. per acre, with an average yield gain of 7 bu. to 10 bu. acre.
The row spacings produce similar ear counts, but twin and 20" rows pick up extra yield through better tip fill and deeper kernel depth. The upper end of the yield response came from soils that need to be pushed and from lighter soils that hang onto water. At the same time, the average yield gains were posted in middle-of-the-road soils.
Seed selection is important with any row spacing in corn production. If you're growing a racehorse hybrid without strong defensive traits, you'll need to protect it. Some disease-prone fields simply need a hybrid with defensive genetics. As always, it is wise to plant your own variety plot to see what works best in your fields at what population. There are limited labels for insecticide in twin rows, and post-emergence ground application is more difficult.
The downside of narrow rows and high populations is that you have to manage disease. With narrow-row corn, the tighter canopy can make disease worse. As with any row spacing, growing conditions are more conducive to disease in some years than in others. Scouting for disease is especially important. Narrow rows have to be treated like 30" rows when it comes to weeds, although the narrower rows close the canopy faster and help choke back the weeds.
Insect pressure can also pick up. Rootworm control in narrow rows requires the most attention. In narrow rows, it's not the rate of insecticide per acre that needs to be calculated but rather the rate per foot of row.
Just as with insecticide, the application rates for starter fertilizer in narrow corn rows should be calculated in rate per foot of row to make sure you deliver enough nutrients to the plants.
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"There are real differences in genetic families and how they respond to twin and 30" rows,” Kavanaugh says.

For example, he says, AgriGold's Family B flexible-eared hybrids tend to maximize productivity at 34,000 to 36,000 plants per acre in 30" rows, but twin yields climb at higher populations (see yield charts at left).

"Our data suggests there's potentially another yield level to be achieved by planting this family of hybrids in twin rows,” Kavanaugh says.

Semiflexible ears, as in AgriGold's Family F hybrids, showed a strong response to higher populations regardless of row spacings. The 2009 plot results put optimum planting population for this hybrid family at 38,000 plants per acre in 30" rows and 43,000 plants per acre in twin rows. Twin-row spacing provided a 6.9-bu.-per-acre yield pop at 43,000 plants per acre.

 "We felt these data points were right on target with past recommendations for this family of hybrids because they tend to be population-driven and less sensitive to inter-row competition,” Kavanaugh notes.

Mixed bag. Bruce Battles, agronomy marketing manager for Syngenta, says population studies by his company indicate there are some geographical differences when it comes to the benefits of narrow rows. That makes sense if you consider that the goal of the practice is to capture sunlight more efficiently and quicker.

Research across the Midwest has shown an advantage to narrower row widths as you move northward in the Corn Belt. The shorter growing season means a larger amount of sunlight is used when corn shades the rows quicker to take advantage of as much photosynthetic capacity as possible. You want 95%-plus sunlight interception at pollination. Sun that hits the ground that is not intercepted by corn leaves means lost potential energy.

"We think there's a big opportunity in using twin rows and narrow rows in a very prescriptive way,” Battles says. "They are a tool that enables hybrid genetics to realize a higher percentage of their yield potential.”

The company plans to conduct a broad swath of additional tests on row spacings this spring.

Battles notes that the tighter canopy associated with twin rows can cause disease pressures, but Syngenta studies are showing some exciting results with fungicide use in high populations.

More plots in 2010. It would certainly be a case of being narrow-minded if Wood and the other farmers who helped seed companies test twin rows in 2009 stopped with one year of data. No worries. Each group plans to head back to the field in the spring to do a double take on twins.


You can e-mail Pam Smith at

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