Soybean School: Are soybeans tougher than we think? Lessons learned from the ’21 season in the West

Frost-damaged soybean seedlings (courtesy Cassandra Tkachuk, MPSG)

2021 will certainly be remembered for the drought in Western Canada, but there were other factors, such as late frost, damaging winds, and new pests that also challenged the soybean crop on the eastern side of the Prairies.

Despite all of those stresses, there was still a crop to harvest in most cases, with yields ranging from 15 bushels an acre in the driest sandy soils to over 50 bushels an acre in areas of south-central Manitoba with heavier soil that received much-needed rain in August. Many fields yielded in the 30 to 40 bushel per acre range.

“I would say the big story is that soybeans are tougher than we originally thought,” says Cassandra Tkachuk, production specialist with Manitoba Pulse and Soybean Growers, in this Soybean School episode, the first of a two-part series looking back on the lessons learned in the ’21 growing season. (Part two will feature Horst Bohner sharing what was learned in Ontario this year.)

In general, soybeans in Manitoba persevered “more than we thought they could,” says Tkachuk. “Some locations received almost no rain and those plants still grew and produced pods. It was really quite remarkable.”

To start the season, in addition to dry conditions, most soybean fields in Manitoba saw a late spring frost on two separate occasions, as the plants were emerging. Fortunately many fields that were smoked by the frost had not fully emerged, and “recovered well through both compensatory growth and the later emergence of those plants,” she notes.

Populations in some areas were further reduced by severe winds a few weeks later. Once again, Tkachuk says she was surprised to see fields that sustained heavy damage regrow and compensate for the loss.

Meanwhile, there were new developments with two pests of concern for soybean growers.

The first-ever discovery of the infamous weed, Palmer amaranth in Manitoba was made in a black bean field in the Rural Municipality of Dufferin, near Carman in September.

“This is one we want to stay on top of. It can grow really fast, really tall, and it’s a prolific, prolific seed producer. So we really need to make sure those plants are not going through the combine at harvest time,” says Tkachuk.

Soybean cyst nematode was also identified for the first time in the RM of Thompson — the fifth municipality where the soil-borne pest has been found in Manitoba going back to 2019.

“What’s unique about this new case is that we saw above ground symptoms,” she explains. “These plants also had visible cysts on the roots, which means there’s a higher population of SCN. So this definitely is a bit of a warning of things to come. It can spread very easily through any method that moves soil.”

Finally, soybeans were among the many crops that saw abnormal late season re-growth as drought-stressed (and confused) plants responded to rain in August and September.

“It was either the odd green plant, small patches ,or a large section of green toward one end of the field. And in one field, we saw prolific bud and flower growth deep into September when the rest of the field was ready for harvest,” says Tkachuk. “These issues appear to be strongly linked to drought conditions during flowering potentially, and the subsequent shift to better moisture in August that triggered growth.”

She says they suspect some of the regrowth in soybeans may be attributed to sterile male plants. They’re also investigating whether a virus could have been a factor.

For many farms in Manitoba that started growing soybeans in the last decade, 2021 marked their first experience growing the crop in a major drought.

“So the way we like to think of it is that we’re rounding out our experience with soybeans and that moving forward, I hope that we can draw from some of these past experiences and make more informed decisions and really just continue to adapt our practices as needed,” says Tkachuk.

Stay tuned for a follow-up Soybean School episode, wrapping up the 2021 growing season in Ontario with OMAFRA’s Horst Bohner.