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A new look at 30-inch rows for soybeans

If you think the case is closed on 30-inch rows, get ready to think again

Soybean growers near the Ontario-Quebec border have tested wide rows, and some have even adopted them already as a way of managing white mould pressure. The disease thrives here. even though agronomists can’t exactly say why. But there’s also more to the 30-inch debate than just mould control.

Based in the eastern end of the province, Scott Banks is an emerging-crops specialist for the Ontario Ministry of Agriculture, Food, and Rural Affairs and he recalls that 2014 was a particularly bad year for white mould in his area.

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“As a general rule across the east, white mould wasn’t anywhere near as bad in 2015 as the year before,” Banks says. “My experience has been, in eastern Ontario, we might get white mould one out of every four or five years but in western Ontario, they might get it one out of every nine years.”

The problem is, you never know if this year will be a bad year, and when one comes along, it isn’t quickly forgotten. “After 2014, a lot of guys were swearing off narrow rows and moving to lower populations,” Banks says.

Some farms get hit more often, which set the stage for regional research completed this past growing season by Paul Hermans, an agronomist for DuPont Pioneer in the Eastern Ontario and Quebec area.

Some of Hermans’ customers have experienced heavy mould pressure every year since 2012. His solution was to organize a multi-site study to assess what could reasonably be done to manage the issue for these farms that seem to have a perennial problem with the disease.

Working at 11 different locations in the region, Hermans designed a trial which tested field-length strips of Pioneer’s 91Y01 to check its response to planting date, seed population, row width and foliar fungicide treatment. Every treatment was replicated twice at each location and, to lend some consistency, all were put in with a Cash IH Early Riser 12/23 split row planter.

“This was so I could just shut the 30-inch row spacing and 15-inch row spacing on or off, to make it somewhat easy,” Hermans explains. “If I were to do the same thing with a drill, it’d be too big a plot.”

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All the early plantings were completed before May 7 and late plantings were done 10 to 14 days after that. Planting population comparisons included 120,000 and 170,000 seeds per acre. He tested 15-inch row widths and 30-inch rows, and he used Acapela or Priaxor for his fungicide tests. Choosing 91Y01 for the trial wasn’t highly scientific, he says. Although it’s a bushier, branchier plant that performs fairly well in the 30-inch row trials that Pioneer conducts before bringing any product to market, Hermans estimates the white mould tolerance of this particular variety is about average. He mostly just picked it because it is the biggest seller in the area and well known.

“We stuck with one variety because it was all the same seed lot,” Hermans says. “If you look at the size of the trial and all the combinations, if we’d gone to two varieties we’d still be out harvesting those plots.”

There was no selection for high-risk mould environments or high-tolerance management practices. This was just a real field test, Hermans says. Most of the fields in the general area have some history of mould, but only one or two may have seen a manure application in recent history. Most locations were simply part of cash crop operations with good growth potential.

“They’re not what I would call low-yielding environments,” Hermans says.

It was no surprise to him that white mould was discovered again at several locations this year. But some of the trial results did surprise him. By full flower, it was hard to visually differentiate between canopy coverage of the two different row widths. At harvest, soybean yields were two bushels per acre higher in wider rows than the narrow ones. Although early planting improved yields overall, the difference between narrow and wide rows was mostly insignificant. Seeding rate also seemed to have little impact and the response to foliar fungicide was mostly similar between 15- and 30-inch rows as well.

“If you look at data from different areas across North America, they would always tell you 30 inches would not yield as much as a 15-inch row,” Hermans says. “I was most surprised by the 30-inch versus 15-inch row width outcome.”

There were a few factors in 2015 that may have contributed to these exceptional results, he theorizes. The first is that it simply was a tremendous soybean growing year in Eastern Ontario. “Soybean yields were up 15 to 20 per cent above average, which tends to favour a 30-inch row I think,” Hermans says.

That could explain why early planted stands only had an average yield advantage of 1.9 bushels per acre. Another critical consideration is the impact that a frost in late May might have had. “There was one grower who lost 30,000 to 50,000 plants per acre in that one particular field because of the frost, and the early planting dates provided 13 per cent lower stands than the second planting date overall, but you had some variance,” Hermans recalls. “I’m not sure I’d see similar results in another year.”

Hermans says he was also a little surprised by the significantly greater response to fungicide applications than the 1.6-bushel-per-acre response observed in 2013. This time, the average yield of fungicide-treated soybeans was 4.5 bushels per acre more than non-treated soybeans, and there was a positive yield response at nine out of 11 trial locations. Maybe previous fungicide trials which depended on only one application instead of the two recommended rates and timings used in this trial can account for this difference. Regardless of the reason, Hermans says he feels no need to repeat this part of the trial again in the coming year.

“I feel comfortable enough in the recommendations on the planting date and fungicides. I think we’ve done enough work there to show the value of planting early and fungicide control,” Hermans says. Next year he’s going to do a simple population trial across Ontario and Quebec to expand on the results of this year’s population comparison. “It’s a 50/50 split between the 120,000 and 170,000 populations, but I think you definitely have to look at lower seeding rates to help manage mould.”

A farmer’s input

Jon Daly, one of the farmers who participated in the trial, agrees that this is also an area of greater interest for him. If this trial proved anything to him, it was that there doesn’t seem to be any one “catch-all” population recommendation, and he’d be interested to see how lower populations would work for his operation.

“We’ve been planting 30-inch rows already for a number of years,” Daly says. “We’ve been running about 165,000 seeds to the acre normally, so I’m thinking we should try backing off on our populations and saving a bit of money on seed.”

Daly says he would also anticipate that it would contribute to white mould control too. “We do have white mould on our farm, but it’s not so big of an issue that I’m worried about it every year.” Daly says that because his crop rotation is mostly two years of corn, followed by one year of soybeans, his risk of white mould is already low.

“In 2009, we upgraded our corn planter and I didn’t want to buy another crazy-expensive machine to do the 300 acres of beans that we did,” Daly says. “We’ve liked 30-inch rows right from the get-go.”

For Daly, a trial that shows wide rows don’t necessarily demand yield sacrifices is music to his ears. He finds wide rows much easier to deal with, even if it does seem like some years he has to be out spraying from May to August. He’s curious to see just how much a lower planting population would have an impact on his whole system. With two years of corn trash to work through, Scott Banks says tillage practices need to be weighed into the equation too.

“We know you can get as good a yield with a lower population, as long as you’ve got decent soils and you get good establishment. That’s not a huge novelty,” Banks says. “But if you get into a rough seed bed, you have to start bumping up seeding rates. Err on the high side.”

Both Banks and Hermans agree that growers should always be cautious about basing their management decisions on one trial or one year’s worth of data. While Hermans’ results this past year are extremely interesting, Banks says there is a lot of data available which clearly suggests it really is an anomaly.

Other research

Horst Bohner, the soybean specialist for OMAFRA, will tell you the established soybean dogma is that if you go to wider rows, you will give up yield potential, which in turn is best mitigated by planting early. The academic community accepted that after many years of research. Still, any opportunity that could reduce seed costs is worth exploring, and so he shared his most recent effort to close yield gaps using a combination of management practices at the SouthWest Ag Conference in Ridgetown this past January.

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By simply adding strip till to a no-till control in the last growing season in Elora, he could improve the yield of his 30-inch-row beans, where the seeding rate was 120,000 seeds per acre, to closely match the yield of 15-inch-row no-till beans, where the seeding rate was 170,000 seeds per acre. Going a little further, by banding phosphorus and potassium fertilizer in those strips, he was able to get a 3.9-bushel advantage over the 15-inch beans. He also tried applying a foliar fungicide with strip tillage and was rewarded with a 6.2-bushel increase over the 15-inch beans. When beans were grown in both 15- and 30-inch rows using strip tillage, the extra fertilizer, and a foliar fungicide, the wide row beans outyielded the narrow rows by two bushels.

That was really unexpected, but Bohner says in another trial location farther north at Bornholm, those same practices could not reproduce these results. At this site, even applying all three strategies could not improve wide row yields so they matched the no-tilled narrow-row beans, and the additional management practices only improved that advantage further with another 4.5-bushel increase.

“I don’t really buy into the story that you have to grow wide row beans to be able to get the benefit of some of the inputs,” Bohner told the audience. He understands the concept that if you grow wide row beans, they’ll have more opportunity to bush, and individual plants are potentially better fed through this strategy than in narrow rows, but he just can’t prove it consistently with evidence. Some varieties are indeed better than others, he confirms, but even when taking varieties into consideration there are still inconsistencies in performance. Says Bohner, “It may well work, but I don’t have good comparisons to show that it doesn’t work in narrow rows.”

This article originally appeared in the February 2016 issue of Soybean Guide

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Amy Petherick

Amy Petherick is a Contributing Editor for Country Guide.

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