Producers may want to adopt their dry-weather mentality when it comes to managing pulse acres.
For many Manitoba growers, it’s time for field rolling once crops like soybeans are safely in the ground. But Dennis Lange, a pulse specialist with Manitoba Agriculture and Resource Development, says rolling should not be automatic. Instead, he argues, producers should be actively gauging whether rolling is needed and, if it is, when it should be done to minimize topsoil risk.
“You need to really assess whether or not it’s going to be a benefit to you, based on the soil conditions that you have that year,” he said.
Why it matters: Field rolling, high winds and dry conditions can be a perfect recipe for wind erosion.
Wind erosion is no small topic when it comes to rolling fields this year. The start to Manitoba’s growing season has been among the driest in recent memory, while strong winds in mid-May did little to help. While parts of the province saw relief leading up to the May long weekend, soils across Manitoba earlier this spring were disconcertingly dry. As of the start of May, satellite data reported through the Canadian Drought Monitor found that much of the province was over 10 per cent shy of normal when it came to saturated surface soil moisture.
“The first question that needs to be answered is, are you dealing with stones? And if the answer to that is yes, well then rolling is definitely going to be a consideration for you,” Lange said.
At the same time, he noted, producers facing both stones and at-risk dry soils have options to roll without watching that soil blow away.
Wind is unlikely to move soil with more moisture and stubble, Lange said, giving little risk for producers wanting to roll right after seeding. In a drier year, however, the producer may want to wait until after crops are out of the ground.
“What that does is it slows a bit of the air movement across the soil surface,” provincial soil specialist Marla Riekman said.
“When you’ve got stones, I get it. You want to push those things down,” she added. “Some areas don’t have stones, and the rolling still happens. Sometimes the big clods of soil, the clay soils and stuff like that, can be problematic, but quite often, once you have a little bit of rain — if you get it — those clods can kind of mellow out and smooth out over time.”
Rolling after crop comes up will not eliminate wind erosion risk, Riekman said, but it will make a difference.
Staging the roll
The first trifoliate is Lange’s typical stage for rolling. Young plants at the hook stage are vulnerable to breaking, he noted, while waiting until the first trifoliate ensures that all plants are well out of the ground.
Producers rolling after emergence will, however, have to pay more attention to the forecast. Producers should choose a day hot enough that plant stalks are flexible (a threshold Lange pegs at 25 C or up). For much the same reason, best practices often have producers rolling during the heat of the day in the afternoon, rather than first thing in the morning when plants have not had time to soften.
“The other thing to keep in mind is you do have a bit of a window in there,” Lange added. “Let’s say your beans are approaching that first trifoliate stage, but you’re 22 C degrees, things are still relatively cool. You’re probably going to want to wait a little bit until things warm up.”
Producers typically have 10 to 14 days between crop stages in which to roll, he said.
Plant population may also play into post-emergence rolling, he noted. A farmer that seeded heavily may be able to risk a few plants without significant economic risk
Measuring losses by eye
Wind erosion can be visibly dramatic, Riekman acknowledged, especially when conditions are dry and wind kicks dirt up in visible waves. Actual soil loss, however, is usually not as bad as it appears.
“If you think about how much soil’s ending up in a ditch and you assume that it came evenly off of the whole 160-acre field next to the ditch, it’s not a whole lot of soil, but there’s a pain because you’ve got to dig that ditch back out,” Riekman said.
The economic costs of that erosion, therefore, are different than what’s measured in topsoil loss, she said, such as the economic cost to the municipality.
It becomes more problematic, however, if the same thing happens year after year, as it has in Manitoba. Now into the latest of a series of dry years, dry soils and wind erosion have become a more common issue.
“We can’t stop the dry,” Riekman said. “We can’t stop the wind. What we can do is try to do what we can in order to make the field less vulnerable to that potential wind erosion, and that means making sure that we’re leaving more residue behind.”
Repeat dry years have seen fewer farmers tilling in fall and more farmers leaving crop residue, she noted.
Producers who are tilling in fall, meanwhile, should not be worried about leaving the field smooth, Riekman advised.
“You want to actually leave it lumpier or bumpier looking than you think it should be,” she said, noting that a smooth field might make for a good seedbed, but also come with a much higher risk of blowing. Soil lumps, meanwhile, work to slow wind over the field.
Those practices, however, are a decision for fall. In the more immediate future, Riekman echoed Lange’s call for producers to consider rolling in-crop.