Farmers in Manitoba are learning more each year about how to grow soybeans, a crop that is gaining popularity in the province.
Soybeans are grown mainly in the eastern half of the province, but there is potential for them to also become an option in western Manitoba and in southern Saskatchewan.
Farmers thinking of planting the crop can benefit from the lessons learned.
According to Bruce Brolley, Manitoba Agriculture pulse crop specialist, variety selection is one of the most important things to consider when growing soybeans.
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Unlike a wheat variety such as AC Barrie that can perform well across much of the Prairies, soybean varieties tend to be much more specific, he said. Different varieties need different numbers of heat units to reach maturity.
To illustrate that point, Brolley described the experiences of Wade Barnes, an agronomist with Double Diamond Farm Supply, who helped organize a soybean variety demonstration in Pilot Mound. Several large strips were planted to soybean varieties with maturities ranging from 2,350 to 2,550 heat units.
All varieties looked lush during a July field day, but when September rolled around, Barnes was struck by the difference 50 heat units could make in maturity and grain quality. That difference reinforces the need to be conservative when choosing soybean varieties for non-traditional areas from Pilot Mound to Brandon, Brolley said.
To help producers gauge adaptability, small plot soybean trials were scattered across western Manitoba this year. Brolley hopes to summarize data from sites that were not devoured by grasshoppers.
Soybeans can produce their own nitrogen through nodules that are formed by bacteria. The bacteria responsible for fixing nitrogen in pulse crops like peas, soybeans and fababeans are crop specific, said Brolley. That means the inoculant rhizobium that works for peas will not work in soybeans.
Another challenge, he said, is that soybean rhizobium are not naturally found in prairie soils so producers have to add them at planting. A full rate tends to be needed the first two times soybeans are planted in a field. After that, growers may reduce the inoculation needed for successive soybean crops in that particular field.
Growers in Manitoba planted 220,000 acres to soybeans this year. That was well above the 120,000 acres planted last year and the 46,000 acres planted the year before.
Experiences with weeds have varied, depending on growing conditions. This year, kochia seemed to be everywhere, said Brolley.
The dry summer and a number of suspected Group 2 resistant kochia helped to make it more noticeable and competitive against soybean crops late in the season.
Brolley said weeds emerging after the soybean’s third trifoliate leaf stage usually do not cause economic yield losses. However, late emerging weeds like kochia, combined with the dry summer, did hurt this year’s soybean yield.
Kochia can be controlled with Edge in the fall or in the spring before planting, Brolley said.
Once soybeans are established, a post-emergent herbicide such as Basagran Forte can be used to control small kochia before they get out of hand and break through the canopy, he said.
If using a Roundup Ready variety, glyphosate can be applied when necessary for kochia control.
Up to two litres per acre can be applied, either in one shot or spread over several applications, depending on the circumstances. The arrival of flowering is the cutoff for applications.
Canada thistle also poses problems for growers. For those growing soybeans with conventional tillage and without a Roundup Ready system, a pre-harvest application of glyphosate the year before planting the soybeans could be the best option, Brolley said.
He estimated the average yield of soybean crops this year in Manitoba likely will be about 28 to 30 bushels an acre. That’s about seven bu. per acre less than the average established from the previous four years.
Soybeans harvested in Manitoba are used for livestock feed or sold for processing into products such as edible oils and tofu.
