The push is on to increase corn yields to a 300-bushel U.S. average. Twin rows may allow corn roots room to grow to capture nutrients and water, while allowing plants to capture more available sunlight.

Have you ever felt like you needed a little more space? If Greg Selbrede's corn plants could talk, the Leon, Wis., no-tiller figures they would have been telling him they felt just a bit claustrophobic.

Just as it was once the norm to plant corn in 38- or 36-inch rows, the days of 30-inch corn may be drawing toward the twilight of its lifespan, says Selbrede, who raises forage for dairy cattle. Selbrede already has moved into the future, as he sees it.

"We were so thick in 30-inch rows, we were getting population top-off," he says. "We couldn't go higher without lessening yields and having standability issues due to thick stands."

WINNING TWINS. Twin-row corn on 30-inch centers may be increasing yields by 8% to 12% over conventional 30-inch rows, says Leon, Wis., no-tiller Greg Selbrede.

When he was ready to trade planters nearly a decade ago, the no-tiller chose to go with twin rows spaced 8 inches apart on 30-inch centers.

Concept Gains Momentum

While the idea is certainly not new — Monosem has built twin-row planters for years and Great Plains is the most recent manufacturer to get on board with the technique — the concept is gaining some momentum with support from seed giant Monsanto.

The very population top-off and plant crowding Selbrede speaks of in 30-inch corn may be the obstacle that prevents corn producers from increasing yields much further.

Monsanto officials have been adamant that corn yields per acre nationwide will need to average 300 bushels to feed a growing world population. That likely means the high-yielding areas of the Corn Belt will need to approach 400 bushels per acre, whereas regions where corn traditionally struggles may need to hit 200 bushels.

"At some point — and we think it's around 38,000 or 39,000 plants per acre — you run out of space in 30-inch rows," says Marcus Jones, technical manager for corn systems at Monsanto. "So the question is, 'Do you go to a narrower row spacing?' and if you do, 'What should that spacing be?'"

Monsanto has 72 locations of plant population studies ranging from 23,000 to 43,000 plants per acre being conducted in 20- and 30-inch rows.

Just this year, it added twin rows to the studies based on the success of twins raised on 38-inch centers in the Delta. Jones says Southern corn farmers have seen a 14-bushel advantage with twin rows on 38-inch centers versus. single-row, 38-inch corn.

"We did not know whether that twin-row concept would work in the Corn Belt," Jones says. "However, the advantage and the appeal of twin rows is that a grower can switch to a narrower row spacing without having to change over his combine head. He simply needs to buy a planter."

"We think twin rows will be an exciting change in agriculture and the wheels of that are already starting to move," says Tom Evans, vice president of sales and marketing for Great Plains. "We are convinced it will take yields to the next level.

"It doesn't require a lot of equipment changes, and I think that's one of the big pluses of twin rows. Basically, you change your planter and other power seed equipment and everything else stays exactly the way it was with a 30-inch corn head."

Better Use Of Resources

Moving the seed in a single row 4 inches in either direction to two rows doubles the spacing of the plants within each row, Evans says. That allows no-tillers the ability to increase seed populations and tighten plant spacing in each row without hurting yield.

Using a 38,000 plant population as an example, Evans says it's easy to see that you are providing more unrestricted root growth and utilizing more resources like sunlight, moisture and nutrients within a field with twin rows over current concepts:

  • Corn plants in 30-inch rows use 14.5% of an acre
  • Corn plants in 20-inch rows use 32% of an acre
  • Corn plants in twin rows use 45% of an acre

In addition, Evans says light utilization by corn plants improves greatly with twin rows. Knee-high corn (V7) in 30-inch rows captures only 30% of available sunlight compared to 68% for 20-inch corn and 90% for twin rows.

He adds that root mass can also be greatly increased in twin rows.

"The root system in a corn plant is basically symmetrical, and that's why plant spacing in the row is so critical to corn," Evans says. "The minute a root system starts to touch a neighbor, it shuts down that root system and it won't continue to grow.

"When we give it more space to grow, we increase its ability to reach out and develop a healthy plant, and pick up nutrients and moisture."

In addition, Evans says they've seen the stalk diameter of twin rows grow to 1.125 inches versus. 0.875 inch in 30-inch rows using the same hybrids.

Equipped For Twin Rows

Selbrede just completed his third year with a 12-row Great Plains Yield-Pro planter with Precision Seeding meters. He says that other than buying the planter, the system has required few adaptations compared to 30-inch, single-row corn.

Post Applications

The one thing that has challenged him, however, is sidedress applications of nutrients or post-emergence herbicide sprays.

"If I want to sidedress, it does cause some issues. I've only got 22 inches and you better have a real thin tire to get through," says Selbrede, who runs 14.9-inch tires on his RoGator. "When we're spraying a post-emerge Roundup application to control giant ragweed in black ground, we've got to be dead-on.

"We will likely be forced to go to GPS because it's a little bit taxing on the operator to be that sensitive when you don't have any room.

"If we are picking at 225 to 240 bushels per acre and we've previously run over one of the 12 rows that goes through the combine, there goes 25 bushels to the acre."

Selbrede's nutrient program begins with 250 pounds of broadcast potash. He applies 40 gallons of nitrogen pre-plant with a disc coulter and sprays 15 gallons over-the-top as an herbicide carrier.

MINIMAL CHANGES. Greg Selbrede says the switch to twin-row corn on 30-inch centers has been minimal. The only new equipment purchase he made was a Great Plains Yield-Pro planter that requires 24 row units instead of 12. The Leon, Wis., no-tiller still harvests corn with his 30-inch-row corn header.

At planting time, he uses a liquid starter at 8 gallons to the acre in a 9-18-9 formulation along with micronutrients like sulfur and zinc, a move he made when he went to twin rows for improved efficiency.

Ear Retention

While he hasn't needed to adapt his 30-inch corn header for twin rows, he does carefully choose his corn hybrids to maintain ideal harvestability.

He uses as much Bt corn as possible and gleans the best information from seed corn growers and suppliers to get a good refuge hybrid to fight off European corn borer.

"I'm moving that outside row over 4 inches, so I have to stop ear drop," Selbrede says. "With the inside rows of the corn head, I've never lost any ears.

"But if you've got a hybrid with a long ear shank, the minute the stripper roll gets a hold of it, the ear has a tendency to go down.

"If that shank can't hold that ear, you will see a few jettisoning out into the nonharvested area, and that's why it was my judgment to use top-of-the-line varieties for refuge acres to fight off European corn borer."

Do You Need A Staggered Seed Pattern?

The concept of diamond patterning or staggering has been developed and driven by Monosem. According to Marcus Jones, technical development manager for corn systems at Monsanto, growers in the South "swear allegiance to it" and say twin rows will not work without it.

It's a concept Monsanto plans to begin researching in the Corn Belt in 2010.

"We think the main idea is to capture more light. However you have those plants configured, if you're capturing more light, then you are going to capture more yield," Jones says. "It might be more the interplant spacing within each row than the spacing between the two rows that matters with yield."

Leon, Wis., no-tiller Greg Selbrede thinks twin rows work simply because corn plants are no more than 8 inches apart from each, whether in the row or the adjacent rows.

"In theory, the diamond pattern sounds good. But I've found so long as I've got 8-inch spacing between corn plants, I'm good," Selbrede says. "At 39,000 plants per acre, I have 8 inches between the rows and at least 10 inches between the plants in the rows. I have a lot more space for root development, water and nutrient uptake, and capturing sunlight."

Monosem says its many years of research have shown that staggered twin-row corn can yield 8% to 15% more than corn in single rows.

Equipment Cost

The only major equipment expense, Selbrede says, is his planter. Rather than 12 units, he needs 24 units to plant twin rows.

"It's minimal, but it escalates the cost. My eyes are wide open to that," he says. "But I can use my 30-inch corn head, my same sprayer and my same forage harvester, so the cost to turn the operation over is minimal."

More Tonnage, More Energy

What has convinced Selbrede to continue with twin rows is the level of corn production. That was borne out by a custom harvester who used a Kemper head to harvest his corn.

Selbrede says the custom harvester also had experience chopping forage from 15-inch corn rows planted with Kinze 15-inch interplant units.

When opening the field — even though the operator thought he would get to the other end of the 40-acre field without filling a truck — he was shooting silage onto the ground three-quarters of the way.

"The tonnage has been spectacular and so has the energy level because our grain-to-stover ratio is far better," he says. "It's the kernels and the ear that make you money and put production levels higher, whether you're trying for pounds per acre of milk or whether you're feeding it to livestock.

"It was this harvester's unsolicited opinion that silage from twin rows looked golden because of the amount of ears to stover. It was his opinion that while the tonnage was there with the 15-inch corn he harvested, there wasn't enough energy in that silage."

In in-field tests he conducted this year, Selbrede said he saw yields as high as 257 bushels per acre in the center of one field, and corn-on-corn yields with a 91-day variety at 218 bushels. That corn was harvested Oct. 19 and had 21% moisture.

"To give you a figure of what I get per bushel, per acre over and above what my expectations would be for 30-inch rows, that's a hard figure to give you factual data on," Selbrede says. "But consistently, with my varying ground, I think I can back this up when I say I'm getting between an 8% to 12% increase. So 10% on 200 bushels would be 20 bushels, and I think I can say that's what we're seeing."

Raising The Ceiling

Selbrede says twin rows have allowed him to raise the ceiling on plant populations, which he feels is the key to higher yields.

He runs plant populations between 38,500 and 39,000 and has toyed with 41,000, but has not seen a noticeable yield response with his hybrids.

"You're not going to get the plant to produce bigger ears because most of your hybrids are fixed ears, so you've got to have more plants," the no-tiller says. "As plant geneticists start pushing the envelope more, we'll be able to go with higher populations.

I'll be in position to use those hybrids when they say populations can go to 42,000."

Jones says plant breeders are getting closer to that goal.

"We know some hybrids respond to plant density better than others. We're sorting that out," he says. "But we know some hybrids take up nutrients more efficiently as you increase populations, so those would be the ones best suited for narrower rows."

Narrower Yet? How About 12-Inch Corn Rows?

Allen Berry is no stranger to experimenting with narrow-row corn, having seen corn yields of 20- and 15-inch corn increase by 10 bushels to the acre over today's 30-inch standard.

It's his feeling that if corn yields are going to hit 300 bushels per acre on average, plant populations will need to hit 45,000. Conceptually, he thinks a 12-inch corn row with plants at 12-inch spacings would be ideal for achieving that plant population and yield goal.

"I think that row spacing would give plants more shoulder room to capture more sunlight and allow roots more room to grow before meeting a neighbor," the Nauvoo, Ill., no-tiller says. "That plant is a factory. It's taking up nutrients. Sunlight is a source of energy. The more you can capture, the better."

Berry believes twin rows are a step in the right direction for raising higher corn yields. He says that when corn plants in 30-inch rows at higher populations get within 4 inches of each other in the row, they become weeds and can't compete.

"The problem is that nobody makes a corn header for twin rows," Berry says. "You get along well if the corn is standing perfect; it all bends in. But if you get downed corn, you may run into difficulties. I think that's a makeshift way to harvest.

"I think twin rows are better, but why not get it right? If we are going to push populations up to 45,000 plants per acre, we almost need to go with a narrower row."

Berry admits 12-inch corn will have its challenges.

Corn Header

Current gear boxes for harvesters are 15 inches or wider, meaning it will take a different design to achieve a 12-inch-row corn header.

"At 15 inches, that's as tight as you can go right now, so we may need some totally different design, kind of like a stripper header for wheat."

Corn Planter

Berry has a 3-year-old, 20-inch-row Kinze planter with pusher units that can plant in 10-inch rows. That allows Berry to plant trials of 10-, 20- and 30-inch row corn with the same planter. He was able to harvest the corn with his 20-inch-row header, and expects to have final data soon.

No Post Herbicides

Berry's philosophy is to stay out of corn fields once the crop is in the ground, but he admits that you will need to use full doses of pre-emergence herbicides, like acetochlor and atrazine combos, for weed control.

"Most of the time, you never have to go back into 15-inch rows, anyway, because the crop will emerge and give quick ground shade so that weeds don't come through," he says. If you need to spray a field with ultra-narrow-row corn, use skinny tires and 120-foot-wide booms to reduce passes.

"Running over the field crossways is the least damaging, or run at a 90-degree angle to the corn row," he adds. "Mostly, stay out of the field so harvest is your next pass. If we go with fungicides, we go with aerial application."

Sidedress Snag

As an advocate of sidedress nitrogen, Berry admits this will be a big obstacle for 12-inch rows. Twin rows and 20-inch rows have an advantage here. He says a time-release nitrogen that can be applied at planting time may be one answer.

Another option may be 32% applications with 40- or 60-foot bars with a 100-horsepower tractor using 9-inch tires on 54-inch rims.

"You could have sidedress openers that inject nitrogen every 40 inches behind coulters. That would minimize damage," Berry says. "Or you might need to set the tractor-planter unit up to have a set of skip rows. That would give you a 20-inch spacing that would be no problem for 12-inch tires."

Residue Management

One of Berry's biggest concerns is maintaining a no-till system in fields with intense corn residue, particularly in corn-on-corn systems.

"We are going to need to mess up those corn stalks with the Bt crusher rolls and process the corn stalk to get it on the ground," Berry says. "Then maybe we are going to have to put some nitrogen on the corn stalks. There may be additives yet to be discovered that may encourage bacteria to work harder to break down trash so we can get it through the planter."

Running turbo discs for minimal soil disturbance at 1 to 1.5 inches deep so that you can plant into untilled ground at 1.75 to 2 inches deep may also be necessary for ultra-narrow-row, corn-on-corn.