Max out yields with shorter-season soybeans

Remember Aug. 22, 2004? For gardeners in the southwest, it is a date that shall live in infamy.

And for soybean growers, it’s a reminder that in Manitoba, the first killing frost doesn’t always come in the third week of September.

Farmers should keep that in mind when choosing a variety that can be crammed into the province’s narrow growing season, says Dennis Lange, a production adviser with Manitoba Agriculture, Food and Rural Initiatives in Altona.

“Maturity is always your limiting factor when growing soybeans,” Lange said at a recent crop meeting.

“Whether you’re growing it in the Souris area or the Red River Valley, you don’t want to sow it too early because you run the risk of frost in spring. And you don’t want to plant it too late either, because then you risk frost in the fall.”

Maturity is gauged by each variety’s 95 per cent brown pod rating in the Seed Manitoba guide. It doesn’t mean you’ll be harvesting at that point, only that the plant is mature, said Lange.

Growing the earliest possible variety allows more margin for error when considering the risk of an early frost. On the other hand, choosing a later variety could end up yielding more bushels to the acre if the year turns out better than average.

But in practice, an early variety stands a better chance of “maxing out” the yield under Manitoba conditions, said Lange.

“So the moral of the story is that in a region where you’re really limited on maturity, don’t just look at the yield,” he said. “Try to find varieties that are in the earlier range because you’re going to max out your yield a lot easier that way.”

The 2013 season is likely to see well over a million acres of soybeans planted in the province, up from this year’s 875,000 acres, which yielded an average of 31 bushels per acre despite widespread drought.

Lange said farmers in the southwest corner of the province should seed soybeans between May 15 and 25. Seed should be at a depth of three-quarters to 1-1/4 inches and soil temperature should be at a minimum of 10 C. Planting at a two-inch depth to hit moisture risks leaving the seed trapped in cold ground, which will delay emergence. Too shallow and the seed could dry out, he added.

A warm spring this year saw cereals and canola seeded early, but soybean growers should resist the temptation to follow suit.

“May is a pretty long month, and the chances of getting a frost are pretty good,” said Lange, noting frost was reported on May 30 last year, and a frost below -2 C for more than two hours will damage young plants.

Plant populations should aim for 180,000 to 200,000 plants per acre, depending on row spacing.

For those looking to save on seeding costs, wider row spacing could be the ticket. Testing of eight-inch, 15-inch, and 30-inch row spacing has found yields were not adversely affected even though the wider spacing covered the same ground with less seed.

An eight-inch row spacing would put in 225,000 seeds per acre, while a 30-inch one would put in anywhere from 140,000 to 180,000 seeds per acre.

At 2,100 seeds per pound, that amounts to total savings of around $20 per acre, said Lange.

“If you’re buying a planter, you’re probably not going to see better yields, but you’re going to save on your seeding rate by cutting your plant population down,” said Lange.

But for farmers who may face disease issues, pushing seeding rates down too far might backfire, he added.

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