Historically, the widest row spacing used to plant corn rows was 40 to 44 inches — limited by the width of the horse. Of course, most growers plant on 30-inch rows, with a few exceptions — like those who plant 20- or 15- inch narrow rows, or wide-row corn in dryland scenarios on the High Plains.
Agronomically speaking, yields have increased with the adoption of 30-inch rows, in addition to higher-yielding hybrids and technology in weed, disease and insect control. So, why are some growers in Iowa experimenting growing corn on 60-inch rows? From Bob Recker's perspective, it's an opportunity to capture more sunlight to boost cover crop growth between corn rows.
"My focus is sunlight — and to really take advantage of sunlight, you need more open space in a cornfield environment," Recker says. "Cover crops don't always produce the most biomass when drilled after corn harvest. That's where the space between these extra wide rows provides an opportunity — an opportunity space."
Promising early results
Recker, a consultant with Cedar Valley Innovation in Waterloo, Iowa, works with growers in Iowa and neighboring states to test out different practices — including wide-row corn with cover crops interseeded. However, before he was experimenting with wide-row corn, Recker was known for his work with strip intercropping — planting four or eight rows of corn, followed by four or eight rows of soybeans, and another four or eight rows of corn — to take advantage of additional sunlight on outside corn rows.
"I've got a good friend who had loaned me some ground for a few years, and he said, 'Go do whatever you want on it,' so I did," Recker says. "One morning over coffee, he said, 'You're doing strip intercropping to capture more sunlight; why don't we plant corn in 40-inch rows like we used to?' Because my planter was a 30-inch planter, I said, 'Why don't I just plant on 60 inches?' I fully expected it to be a train wreck — it wasn't. It was really good. That was 2017."
In fact, Recker's 2017 trials, and follow-up, on-farm trials with 12 growers in 2018, revealed corn on 60-inch rows yielded, on average, within 95% of 30-inch rows.
Focus on soil health
Since then, Recker's goals have shifted to accumulating more cover crop biomass. This year, in several fields in Black Hawk County, he's planted corn on 30-inch rows with and without cover crops, and 60- and 90-inch rows with six-way and 14-way cover crop mixes. These 90-inch rows include single rows and twin rows. In the case of wide rows, it's not the corn that benefits most from the sunlight — it's the cover crops.
"The term we've come up with is, this is an 'opportunity space,'" Recker says. "If we could get the corn where it would be just about as profitable on wide rows as it is with 30-inch rows, this is an opportunity for growing soil, growing forage, even growing produce to get more revenue."
The 14-way mix includes cowpeas, forage soybeans, crimson clover, sweet clover, Italian ryegrass, pearl millet, forage collards, radish, turnips, buckwheat, flax and safflower. Meanwhile, the six-way mix includes hairy vetch, red clover, annual ryegrass, rapeseed, buckwheat and different pulses.
Typically, Recker and other growers planting on wide rows shoot for the same overall field population. So, for a population of 30,000 plants per acre and single, 60-inch rows, a 30-inch planter would need to have very other row shut off, and every other row planted, for a population of 60,000.
"I like to drill just as soon as I can after the corn's up. I believe once the corn is about 6 or 8 inches, it's locked in its yield potential and it's ready to go. I don't want the cover crop to compete with the corn when it's locking in. But if the corn is up at V4, V5, it's going to win," Recker says. "That's the key — getting the corn to win the race, and the cover crop to finish a close second."
Bad year for corn, good year for cover
Of course, with the lack of rain in northern Iowa this year, Recker notes the corn won't be harvested — even the corn planted on 30-inch spacing with no cover crop is showing below-average yields. This plot west of Janesville received about 13 inches of rain, compared to an average of 24 inches, between April 1 and July 31. Meanwhile, the wider the rows, the more the cover crops thrived.
"We planted late in May, had a little bit of rain, and then nothing. That's where the cover crops are a risk management strategy against unfavorable weather patterns that discriminate against corn, but a multispecies cover crop might be able to adapt. I'm really intrigued with how dramatically different the multispecies was compared to a simpler mix. So it adapts," he adds. "To me, diversity is a pretty interesting risk management strategy. Your financial planner would say, don't put it all in one basket. You need a diversified portfolio. This is a diversified crop portfolio."
Mike Cook, who farms in and around Waterloo, is a prime example. This is Cook's first time growing wide-row corn — although he previously worked with Recker to experiment with strip intercropping. This year, they replicated the same mixes on a plot Cook farms. Similar to Recker's plot near Janesville, his wide-row corn is a loss this year — due in large part to persistent dry, hot conditions.
"I've got light, sandy soil, we didn't get rain when we needed it, and we had a number of consecutive days with 90 degree temperatures — which is unusual, especially in northeast Iowa," Cook says. "That's a death warrant for corn on poor soils if you don't have rain."
Putting opportunity space to work
However, Cook has grown produce in Waterloo since 1986, and has used the opportunity space with 60-inch rows to grow produce like watermelons, squash, radish, turnips, turnip greens, purple hull peas, green beans and ornamental pumpkins to sell at the local farmers market.
"It did really well in the wide rows. We have some really good stands of turnips," Cook says. "Those were some of the biggest turnips and turnip greens I've seen that we harvested this year."
And, Cook has seeded cover crops between the rows as well — which helps suppress weeds and prevent erosion. It's a natural next step for Cook, who is in his sixth year of no-till, and has seeded a cereal rye cover crop on part of his acres for the last three years, which, he notes, has helped add biodiversity to the soil and improve soil water infiltration.
That's why Recker says even with a slight yield loss, wide-row corn can be profitable with a cover crop, produce, forage crop or other use of the "opportunity space."
"My data says you can take a 5% yield loss, plus or minus 10%," Recker says. "There are people who are getting more. Mostly, people are getting less. If you aren't managing weeds, if you aren't tweaking the population, and if you aren't doing a good job of planting, you're going to get a lot less. So it's not for amateurs. It's not an easy button."
Wide rows present grazing opportunity
Jim Johnson, a sales consultant with propane supplier Sport Wade Inc. in southern Iowa, got started with wide-row corn in a similar, serendipitous manner to Bob Recker.
"We started in 2017 with a Practical Farmers of Iowa [PFI] trial, planting covers into 30-inch corn rows. When we were doing this trial near Lamoni, the grower stopped for 18 or 20 minutes, and it skipped him over about 15 inches. We had a 45- to 60- inch gap, so I just went ahead and planted cover crops in it," Johnson says. "In 2017, we had a really dry, hot summer. In the 30-inch rows, we measured about 300 pounds of biomass per acre, but we had about 2,000 to 3,000 pounds [on a dry matter basis] in that wide gap, and it was visible."
He's currently working with six growers in the area — usually on plots anywhere from 10 to 30 acres. Some fields he's working with have shown anywhere from 10,000 to 20,000 pounds of biomass per acre — averaging out around 15,000 between the rows.
"Bob Recker was a big inspiration," he adds. "When we had that skip and saw the results, I went to a PFI meeting and listened to Bob Recker, and it was like a lightbulb went off."
Working with PFI, the Iowa Cattlemen's Association, the Natural Resources Conservation Service, and people like Recker and Washington County grower Mitchell Hora, Johnson has continued to experiment, planting cover crops into wide-row corn around V4 to V6 — and planting the same day as corn. However, he notes he's working on a one-pass system to plant corn and the cover crop simultaneously with the same machine.
Cover crop mix, high populations
He typically seeds a mix of cover crops in these wide rows — including turnips, radishes, annual ryegrass, red clover, mung beans and cowpeas.
Similar to Recker, Johnson is planting higher populations — 60,000 plants per acre — on every other row, with the goal of achieving the same population of 30,000 plants per acre as with 30-inch rows.
For Johnson, it's not about yield; it's about return on investment.
"If we're not losing yield, and even if we lose a little, we still gain some root action — and we're breaking down nutrients," Johnson says. "It all goes right back into that row, and if we move over 30 inches and grow corn again — because we planted a legume cover crop where we normally would the other row of corn, we can take advantage of that nitrogen."
Johnson says on the fields he's worked with, growers have experienced anywhere from a 15-bushel per acre loss to a 10-bushel gain.
"In one field with 60-inch rows, we had about 15,000 pounds per acre of biomass growing, and the yield monitor was showing 200 bushels per acre in parts of the field, compared to 180 bushels on 30-inch rows in a nearby field," he says. "This year, we've got two 60-inch row plots we're comparing to 30-inch rows. On both of those plots, we didn't seed a cover crop, but it looks like we're going to be right in the ballpark in terms of yield."
It goes beyond agronomic benefits, however. Johnson says several growers he's working with raise cattle and plan to strip-graze the cover crops after corn is harvested. From this standpoint, wide rows with cover crops present an economic advantage as a forage resource.
"We have the advantage here because we have livestock — everything from cattle to sheep. So we're looking at diversifying even more," Johnson says.
Different goals, different approaches
Mitchell Hora takes a different approach to his wide row setup — turning off every third row on the planter, planting two rows, and skipping one. This means every other row is 30 inches wide, and every other row is 60 inches. Hora shoots for the same population per acre as his regular fields, and increases the population to 50,000 plants per acre for the rows that are turned on.
Hora has been planting cover crops on wide-row corn on his Washington County farm since 2019, and the corn he harvested this year was planted where the 60-inch gap, with a diverse cover crop mix, was seeded two years ago. Typically, he tries to seed cover crops when the corn is around V3 or V4.
"This year, we interseeded cover crops on June 7 at the field day on our farm, and the corn was at V3," Hora says. "We were dry earlier in the year, but we've had amazing moisture through the summer — and the cover is just awesome."
Hora's goal is to introduce as much diversity into the rotation as possible to stimulate soil biology and build soil health, giving a chance to mineralize and sequester nutrients for the corn crop two years later. With that in mind, he has planted a range of diverse cover crops in wide rows, including cereal rye, annual ryegrass, cowpeas, sunn hemp, flax, tillage radish, turnips, buckwheat, hairy vetch, rapeseed, Russian brassica, Balansa clover, crimson clover, and various other clovers. This usually amounts to about 40 pounds of seed per acre at a total cost of around $35 per acre.
"The following spring after the cover crop, I've seen a freeing up of available phosphorus and potassium — over 2,000 pounds — and over 400 pounds of nitrogen," Hora says. "Some cover crops have exudates that directly impact nutrient availability, like buckwheat. Buckwheat doesn’t form mycorrhizal connections, but directly secretes an acid to help break down the soil and free up phosphorus. Because of that, we don't apply any P and K. Some of my corn has only 140 pounds of N applied on it. Besides that, there are only 1.5 passes of herbicide — no insecticide, no fungicide."
Maintain yield on wide rows
However, Hora notes since he's not a livestock producer who can use the cover crop biomass as a forage resource, his goal is to not lose yield on wide rows. And this year, despite giving up about 5 bushels per acre, he notes yields are promising.
"From the yield monitor, the whole farm did over 200 bushels per acre. In the 60-inch rows, we harvested around 190 to 195. So it's looking like we might have lost some bushels this year — part of it due to a dry spell early on. We also had some weed issues that knocked some things a little bit," Hora says. "That's still really good for growing 60-inch corn with fewer inputs."
This year, Hora also planted wide-row corn into a field half-seeded with perennial red clover, and half-seeded with winter wheat. He's using the same "plant two, skip one" approach he's using on his other 60-inch fields. Next year, he'll plant corn in the 60-inch gaps where the red clover is this year — allowing it to use nitrogen fixed by the perennial legume crop. "Where all the red clover has been growing all year and is thick and aggressive, that's where the corn will be planted next year," he says.