Glacier FarmMedia — Provincial pulse and soybean specialist Dennis Lange says the window for planting soybeans in Manitoba is getting wider.
“In the past, one of our big concerns was planting soybeans too early,” he says. “That was our initial discussion a few years ago.”
Soybeans are susceptible to frost, and historically, the risk of frost has been significant into the third week of May in many parts of the province — but that risk “has definitely diminished,” he says.
As a result, farmers have been planting soybeans earlier; nine per cent of Manitoba’s expected soybean acres for 2023 were already in the ground as of May 16 that year.
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The window has opened in the other direction as well. Manitoba crop insurance deadlines for planting soybeans and several other crops were extended in 2022 to account for late seeding due to spring storms.
At the time, Manitoba Pulse and Soybean Growers executive director Daryl Domitruk said those deadlines could stand to be reviewed anyway, as improvements in early-maturing varieties have changed the game.
In 2023, Manitoba’s insurance deadlines for planting soybeans ranged from May 30 in Area 4 to June 8 in Area 1.
Wider though the window may be, Lange says the ideal time to plant is still the last week of May in most areas. A heat-loving crop, soybeans are more susceptible to disease if they linger in cold soil too long.
“Once we get some good warm conditions, the soybeans will come out of the ground really quick,” Lange says. “In seven to 10 days, we start to see beans popping up, and that’s what you want to see.”
As for planting depth, “a good target to work with is in the range of three-quarters of an inch to an inch and three-quarters. Ideally, you’d want to be in that mid-range, so about an inch and a quarter into good moisture.
“The deeper you go, the colder the soil is, and the slower they’re going to come up. There have been some years when it’s been a drier spring and growers have had to go down to two inches. That’s not something I typically would recommend.”
He cautioned against planting shallower than the recommended range. He has seen farmers plant in the half-inch range when rain is in the forecast, hoping to get beans out of the ground sooner.
“If you don’t get that rain, there may be enough moisture for the seeds to germinate, but you may have higher levels of desiccation of the seeds and a poorer stand just because that seed imbibed some moisture, but then dries off because it’s not enough for continuous growth.”
Seeding rates are another consideration.
“You want to have a stand establishment of between 140,000 and 160,000 plants per acre,” said Lange. “That’s the range where you’re going to maximize your yield.”
Lange noted solid seeding — anything narrower than 10-inch rows — may result in higher seed mortality from air seeder damage. In such cases, farmers may want to aim rates a little higher.
“So they should be planting at that 200,000 seeds per acre range to get that 140,000 to 160,000 plants per acre,” he said.
On the other hand, planting in the 170,000 to 180,000 seeds per acre range should be sufficient to reach target density.
“Regardless of row spacing, your target range still stays the same. If you’re noticing a lot of splits in the seed, or if you know the seed is very dry and you’re putting it through a system that could damage that seed a little bit, you want to compensate your seeding rate for that just to make sure you’re in that target range,” Lange said.
“I have seen years where growers are in a bit of a rush and they put it through the air seeder, and all of a sudden, instead of having 140,000 plants, you’re under 100,000 plants.”
