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Prairie soybeans still heading west

The relatively disease- and pest-free honeymoon may be coming to an end in Manitoba, but soybeans continue their march west

It was yet another record year for Manitoba soybean acreage, with 1.6 million acres of what is now the province’s third-largest crop behind wheat and canola. But as the crop becomes more established, and with the wet conditions this year, diseases are starting to show up, which is presenting challenges for agronomists and changing priorities for research.

“We have seen a lot of phytophthora and fusarium root rot and sclerotinia white mould this year, especially in eastern Manitoba where we have more intense frequency of soybeans in rotations and had wet spring soil conditions that weren’t ideal for crop establishment,” says Kristen Podolsky, production specialist with the Manitoba Pulse & Soybean Growers (MPSG). “The focus this year has been to help growers identify it and understand what the options are to manage it.”

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Despite the increase in disease, the jury is still out on the effectiveness or economics of fungicides. Researchers continue to evaluate types and timing of application, but to date they’ve not seen a consistent response to fungicide in Manitoba trials.

However, cultural practices can reduce the risk of disease in following years. To avoid phytophthora root rot, producers can select a variety with genetic resistance for their next soybean crop on land that had the disease. For sclerotinia white mould, it’s important to think about the crop canopy.

“Practices that increase airflow will potentially reduce the risk for white mould, such as a wider row spacing or growing shorter varieties which have less vegetative growth,” Podolsky says.

It’s also important not to use too high a seeding rate. The recommendation is a target of 140,000 plants per acre, which means seeding at between 170,000 to 200,000 seeds per acre depending on the type of seeding equipment. “Not only is that a good target plant population for preventing disease, it’s also a good economic target as well,” Podolsky says.

Saskatchewan soybean acreage dropped slightly to 235,000 acres this year after reaching 270,000 acres in 2014 and 2015, but provincial special crops specialist Dale Risula thinks it will increase again next year.

“We had one year with a shorter fall and earlier frost, and that may have put some people off, but there are still lots of people who want to try them.”

How far west?

Like Manitoba in the first few years, Saskatchewan is still relatively free of soybean disease. But a big question is how far west and north the crop can move into areas with cooler nights and fewer heat units.

Earlier maturity has been a major focus in most soybean-breeding programs in Western Canada, and Risula says some new early varieties set for release in 2017 are looking promising in variety trials.

Many varieties currently available in Saskatchewan require a full growing season, but one grower says it’s not the end of the world if frost comes before soybeans mature because it won’t necessarily result in downgrades.

Kevin Elmy has been growing soybeans since 2001 near Saltcoats, Sask. He says he has successfully grown 2350 heat unit (003) varieties with no problems, and his 10-year average yield is 29 bushels per acre.

“Soybeans start flowering ideally by the 20th of June and they’re setting pods from seven to 10 days after first flower, so they always have a base yield of around 10 bushels per acre. After that Mother Nature influences what we get for yield.”

A late-planting study in Manitoba is trying to determine whether current crop insurance seeding deadlines are still appropriate given the availability of very early-maturing varieties. The study compares very early-, early-, and mid-maturing varieties planted throughout June in three different maturity zones in Manitoba. “The study emphasizes the importance of selecting the earliest-matur­ing variety available when it comes to late planting,” Podolsky says.

Elmy considers soybeans a low-risk crop if growers get the agronomy right. “Cutting seeding rates back will delay maturity, as will seeding too early, because they’re a warm-season plant. They need warm soil — at least 10 C. If you treat them like peas, you’re going to have a wreck,” he says. “Ensure that P levels are decent in the soil, and after that, they’re on their own.”

New findings on inoculation

Double inoculation of soybeans has been a standard recommendation for new growers on the Prairies, because soils that have never grown soybeans before do not have the native population of rhizobia bacteria needed to ensure nodulation. But MPSG wrapped up a study this year that showed no economic yield response to double inoculants in established soybean fields, prompting some new guidelines for Manitoba growers.

“It is still very important to double inoculate the first few times you grow soybeans, but if you have grown at least three crops of soybeans on a field, and the last soybean crop was within the last four years, it’s more economical to move to single inoculation than double,” Podolsky says.

“But you need to know your field history and what the parameters are. If you have had significant flooding or drought we would encourage you to double inoculate because those conditions can be stressful on the rhyzobium. Even if growers have been growing soybeans for many years, they should also double inoculate in any fields if they saw lower nodulation in a previous year.”

Prefer well-aged P

Adequate phosphorus is critical for soybeans and several studies are looking at response to various types, rates and placing.

“We haven’t seen a great deal of response but soybeans are second only to alfalfa in terms of their ability to scavenge soil P but they don’t like fresh P,” says Garry Hnatowich, research director at the Irrigation Crop Diversification Corporation (ICDC) at Outlook, Sask. “They prefer a P source that’s more mellow from previous applications of P fertilizer. Farmers might be better off putting higher P on their preceding crop and using that residual when they rotate into soybeans.”

Jeff Schoenau’s research at the University of Saskatchewan suggests the seeding system and field conditions play an important role in seed-placed P and seed injury.

“Under low seedbed utilization — using a narrow opener and a wide row spacing — we found that soybeans could tolerate up to 20 pounds of P205 per acre, but above that we started to see some reductions in germination and emergence,” he says. “I believe tolerance to seed-placed P depends on conditions. Wet conditions in the field certainly tend to temper the effect of the fertilizer injuring the seed, or germination or emergence.”

But watch for drift

Roundup Ready 2 Xtend soybeans with tolerance to both glyphosate and dicamba will be available for western Canadian growers next year, and will also appear in variety trials. Although they provide more weed-management options, Manitoba Pulse & Soybean Growers production specialist Kristen Podolsky says growers may need to wrap their heads around a different production system.

“They will need to consider the herbicide products that they are using, and potential drift problems; so they’ll need to be more aware of what’s growing around their soybean fields. Not all soybeans are equal,” she says.

Few dockage worries

Soybean growers have options to sell the crop to processing plants in Saskatchewan, Alberta, Manitoba and the U.S., and Saskatchewan soybean grower Kevin Elmy says he loves selling beans because rarely does he get more than one per cent dockage.

“Cracks and splits are not dockage because they’re making meal out of it, so as long as you haven’t powdered them they’re still a salable product.”

This article originally appeared in the October 2016 Western issue of the Soybean Guide.

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