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Soybeans raise tillage issues

As the low-residue crop creeps into new areas, new techniques are needed

Agriculture researcher Yvonne Lawley doesn’t want Manitoba farmers to rethink soybeans — she wants them to consider techniques to incorporate them into their production system more safely.

The University of Manitoba professor says the crop’s earned a reputation as a soil buster, and at times that’s warranted. But they also bring a lot to the table for growers, she added.

“They diversify rotations, help put a bit more time between canola crops, and are another profitable option,” Lawley said. “But they can also mean more tillage, which can mean more erosion, especially wind erosion in this window right now — March, April and even at times into May.”

Regional variation

Lawley says there’s two issues at play, depending on what part of the province a farmer is living and working in, but they’re both related to tillage.

For the traditional growing area in the Red River Valley, there’s the prevalence of using fall tillage to control crop residue on the heavy clay soils of the region. That well-established practice is meeting a much lower-residue crop in soybeans, and the results are more wind erosion.

This is a bit of a unique thing for this growing area,” Lawley told the Co-operator. “They’re growing soybeans in other parts of the world and not doing this, so you have to ask, ‘why is that?’”

For the newer regions there’s the ongoing concern of getting a longer-season crop to maturity, and frequently farmers are looking to tillage to dry out and warm soils in the spring.

“When farmers are trying their first soybean crop, that’s always their biggest concern,” Lawley said.

In earlier years that was a much bigger concern for growers in the valley too, but the latest varieties are climatically better adapted, and she urges farmers to periodically revisit their use of spring tillage to evaluate if it’s necessary.

“As we get better-adapted varieties, it’s a risk that we’ll just keep using tillage because it’s how it’s always been done,” she said.

Research results

Lawley has been heavily involved in a number of research trials looking at finding the ‘right’ amount of tillage for soybeans. She says it’s still early days, but there are some trends emerging.

For valley soybean producers she recommends investigating direct seeding for these crops, if equipment can be adapted to try it.

“They do it in other parts of the world,” Lawley said. “It is a low-residue crop, and I think this should be possible.”

Longer term, she says cover crops will likely play a role in holding soil down following harvest and residue management. That could even take the shape of novel arrangements, like sowing fall rye the year before soybeans, then sowing soybeans into that the following spring.

“It delivers a few benefits, including transpiring water and improving trafficability of the land,” Lawley said.

Growers outside the Red River Valley may want to consider the promising technique of seeding early, into tall-standing straw.

“Leaving the straw standing more means it’s not on the ground, creating a mulch,” she said. “Sunlight can still get through the stubble and warm the soil.”

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Gord Gilmour is Editor of the Manitoba Co-operator.

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