Soybean research underway

From variety development to agronomy advice, soybean research is bringing new options

In 2015, soybean acres in Manitoba increased by more than four per cent over 2014, to 1.34 million acres.

“We have doubled our soybean acres in Manitoba over the past five years,” says Kristen Podolsky, production specialist with Manitoba Pulse & Soybean Growers (MPSG). “That has been a direct result of their ability to tolerate wet soil conditions in the Red River Valley and breeding programs, which have given us more, shorter season varieties, which also have good yield potential, to facilitate soybean expansion into western Manitoba and Western Canada.”

Soybean acres took a dip in Saskatchewan from 300,000 acres in 2014 to 250,000 acres in 2015, likely due to a combination of frost damage to some fields and economics favouring canola over soybean in some areas. But last year’s soybean yields were higher than growers had ever seen in the province, says Sherrilyn Phelps, agronomy and seed program manager for the Saskatchewan Pulse Growers (SPG). Soybean production in Saskatchewan is slowly increasing as shorter season varieties come to market, but most production is still concentrated in the southeast corner.

Soybeans are attracting a lot of attention from Prairie researchers looking to develop shorter season varieties.

Variety evaluation trials organized by Manitoba Agriculture, Food and Rural Development and MPSG, in co-operation with the Crop Development Centre (CDC) at the University of Saskatchewan, have been evaluating early maturing soybean varieties for more than a decade. This year the trials involved 12 sites in Saskatchewan and six in western Manitoba, and assessed 36 different entries from breeding programs across the country.

“This material is at least one level shorter maturity than what would typically be grown in the Red River Valley,” says Dr. Tom Warkentin, a pulse researcher at the CDC. “Even in that case, when we assess days to maturity the range that we’re publishing in the Saskatchewan Seed Guide is going from 118 up to 128 days. So that’s still quite a long season for this part of the world.”

Warkentin says Saskatchewan growers have been fortunate the last few years that most of these varieties have reached maturity before a killing frost, but they’ve also had seasons where the first killing frost has been later than average. “We feel that there’s still a big need to select types that have a little shorter duration while still maintaining good yield,” he says.

Pests and Disease

Although much of Manitoba has been in a wet cycle for the past few years, growers need varieties that can perform in all conditions. MPSG is funding a research project at Agriculture and Agri-Food Canada’s Brandon Research Centre, led by Dr. Ramona Mohr, to assess soybean varieties under varying moisture conditions.

Although soybean pests, such as soybean cyst nematode and diseases such as sclerotinia white mould are not as problematic as they are in the U.S., researchers are keen to keep ahead of the curve by building resistance before they become a serious concern for growers in Western Canada.

More varieties are coming out that have soybean cyst nematode resistance, as well as resistance to Phytophthora root rot, which can be caused by multiple different races, and no one yet has a handle on exactly which races of Phytophthora are present in soybean fields across the Prairies. “We have been funding a project over the past two to three years with Dr. Deborah McLaren, a pathologist who has been surveying fields and collecting samples,” says Podolsky. “We are expecting this year to release what the most prevalent races of Phytophthora are in Manitoba soybean fields, which will provide a great tool for growers to match the resistant varieties that are available.”

Jordan Bannerman is leading research at the University of Manitoba to determine the best ways to measure the natural enemies (NEs) to soybean aphid present in farmers’ fields, to determine whether spraying is economically viable. Farmers can use a Dynamic Action Threshold (DAT), developed by Dr. Rebecca Hallett at the University of Guelph, to estimate whether or not the NEs are likely to reduce aphid numbers to the point where spraying is not necessary. Four Ontario soybean growers recently tested the DAT system. Based on the results, none of them chose to spray their fields, which never reached the injury level threshold of 675 aphids per plant.

Iron Deficiency Chlorosis (IDC) can also be a problem, particularly during wet growing conditions. “On the prairies we have calcareous soils and a higher pH which can increase problems with IDC, so IDC tolerance is another important attribute that growers should look for in today’s soybean varieties,” says Podolsky. Research is currently underway at AAFC in Morden, Man. to evaluate soybean breeding lines for IDC resistance.

Managing White Mould

There are only four fungicides registered for control or suppression of sclerotinia white mould in soybeans in Western Canada: Acapela (DuPont), Priaxor (BASF), Allegro 500F (Syngenta) and Delaro (Bayer CropScience).

Dr. Michael Wunsch of North Dakota State University, speaking to agronomists at the Manitoba Agronomists Conference, said U.S. research has shown an average reduction of around 45 per cent with a fungicide application at optimal timing. But, he adds, getting good coverage with a fungicide is vitally important to control white mould.

Wunsch said fungicides must be applied prior to sclerotinia infection but must also be applied when it is possible to achieve the fungicide coverage that is needed for that fungicide chemistry to provide satisfactory sclerotinia control. Results of field trials conducted to-date strongly suggest that the fungicides currently available in Canada must be applied at bloom initiation (R1 growth stage) to achieve satisfactory control of sclerotinia.

Shorter season varieties are generally less susceptible to white mould than longer season varieties, but the timing of wet weather matters in terms of white mould infection. Wunsch’s research under irrigation has shown there is a higher likelihood of infection if soils are moist during late vegetative growth and bloom initiation, and cool, wet, weather occurs during bloom and early pod (R2 and R3) stages. How precipitation falls is also important. “If you get frequent, light rainfall events you are much more likely to have severe white mould than if you get infrequent, heavy rainfalls even if the amount of water overall is the same,” says Wunsch.

Wider row spacing reduces the risk for white mould, but may not compensate for the yield drag generally associated with wide rows. Wunsch emphasizes that western Canadian soybean growers will have to experiment with different management strategies to determine what works best under their own conditions.

On-farm research studies conducted in eastern Manitoba have shown a significant yield response to fungicide application in only three out of 21 trials conducted from 2014 to 2015. “We aren’t seeing a consistent economic response to fungicide for several reasons,” says Podolsky. “First, sclerotinia although present at low levels, has generally not been yield limiting in the majority of Manitoba fields and the products being used are not registered for control of this disease in particular. Secondly, the most common foliar leaf diseases that are present are bacterial blight, which is not controlled by a fungicide and septoria brown spot which again is generally not yield limiting. I think the focus going forward needs to be on root rots and late-season stem diseases which have more potential to impact yield as we grow soybean more intensively.”

Managing weeds

Weed management in soybean is relatively straightforward, as most varieties available in Western Canada are glyphosate tolerant.

However, herbicide-resistant volunteer canola can be a problem in soybean crops. A team at the University of Manitoba led by Dr. Robert Gulden is researching different herbicide options and the use of tillage to help reduce the canola seed bank. An early fall tillage pass encourages canola seed left behind in the field to emerge and be killed off during the winter, said Gulden, who shared some of his research findings at MAC. He has also found that herbicide timing is important. Applications are most effective in preserving yield if they are made during the critical weed-free period for soybeans, but Gulden’s team is still trying to determine exactly when that is for Western Canada.

Acreage on the rise

What’s really been driving the increase in soybean acres, particularly in Manitoba, has been a combination of environment and economics, says Podolsky. “Soybean’s ability to adapt to wet conditions — which have been very prevalent over the past five years — has likely been a driving factor, and they have also been able to deliver good yields that are comparable, if not better, than other crops in rotation,” she says. “Soybeans also spread out the busy seasons for farmers, and we continue to have a good market for soybeans so that has been important as well, but overall it has been the ability to grow well in wet conditions and compete economically with other crops that has attracted growers to soybeans.”

About the author

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Angela Lovell is a freelance writer based in Manitou, Manitoba. Visit her website at http://alovell.ca or follow her on Twitter @angelalovell10.

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