Coming up with an ideal recommended canola seeding depth is a bit like the Goldilocks story where the bowls of porridge ranged from either too hot or too cold. When it comes to seeding canola, the ideal recommendation can’t be too shallow or too deep, but what is the just-right depth recommendation — most likely somewhere in the middle?
Seeding between one-half to one inch deep appears to be a fairly safe recommendation. But how about aiming for three-quarters to one inch? Some say 1 1/4 inches deep is a good target. And yet others have found a depth of 1 1/2 inches works, especially if you’re trying to seed into moisture.
Pretty well everyone agrees seeding at two inches of depth, even if there is moisture, is just too deep. It puts too much pressure on the energy within those little seeds to push their way to the soil surface.
The original canola seeding recommendation, “seed shallow into a firm, moist seed bed” isn’t necessarily wrong, but experience over the past 40 years and perhaps with more recent weather patterns has shown farmers can aim to seed deeper than half an inch to achieve good, if not better, yield results.
Coming up with a new, perhaps official, recommendation is still in discussion across the canola industry, says Autumn Barnes, agronomy specialist and stand establishment lead for the Canola Council of Canada (CCC).
“We’ve seen in recent seeding seasons there can be a risk of seeding too shallow,” she says. “It is very easy for that top quarter or one-half inch of soil to dry out. So, we’re recommending farmers avoid really shallow seeding.”
The CCC has set its seeding depth recommendation at between half an inch and one inch of depth. And Barnes isn’t sure if the recommendation will go much deeper.
“If we recommend a deeper seeding depth, my concern is about consistency,” she says. “There are seeding systems that are 60, 65 and even 75 feet wide, and how well have they been calibrated? Have they been calibrated front to back and side to side? Is every drill run placing seed at the same depth?”
Depending on drill calibration and speed of travel at seeding, it could easily result in a wide variance of seed placement, which could lead to increased seed mortality and uneven germination. “Whether the seeding depth recommendation needs to be changed further is something the industry is still in conversation over,” she says.
Rob MacDonald, manager of the BASF Agronomic Excellence canola research program, agrees it is difficult to select a specific seeding depth that works for all farms in all soil zones, under all spring moisture conditions — there are just too many variables.
As someone who’s been seeding canola for more than 30 years, he used to believe “if I didn’t have a few seeds on the soil surface I was seeding too deep,” he says. He’s changed his thinking. He avoids shallow seeding — that being a half inch deep or less. It is a perilous zone for seed especially if conditions dry out. Depending on soil and seeding conditions he mostly has a zone for seed placement — somewhere between a half to one inch and maybe even as deep as 1 1/4 inches on the maximum side. “Rather than there being an ideal recommended seeding depth, I believe it is more of an ongoing discussion,” he says.
Seeding depths vary
In 2018, Richardson International at its crop research Kelburn Farm south of Winnipeg seeded its canola trials at a depth of 1 1/2 inches to reach moisture in a dry spring. Company researchers were impressed with yields that ranged from 45 to 50 bushels per acre during a relatively dry growing season.
Out on Alberta farms, John Mayko, for example, aims to seed canola ranging from three-quarters to one inch in depth on his grain and oilseed farm near Mundare, in north-eastern Alberta, while in southern Alberta Matt Gosling says he favours going even a bit deeper, aiming for 1 1/4 inches in depth.
Mayko, who owns Apex Agrology Services Ltd., as well as farms, says several factors come into play, but most years he aims to seed on the deeper side (about one inch) to place seed into moisture. “If we have a wet growing season like we did a couple of years ago, you could go really shallow, perhaps even have some seed on the soil surface, and under wet conditions it would grow,” he says. “But most years there is a risk of the top layer drying out, so we seed a bit deeper.”
He says the other factor to consider is soil type. On heavier, clay soils there is a risk of soil crusting making it difficult for seedlings to push through — they need all the energy the seed can provide. “I wouldn’t hesitate to seed deeper if I was seeding into sandier soil where there is little risk of soil crusting,” he says.
Mayko seeds with a Bourgault seeding system with knife openers. He places some phosphorus with the seed, but most fertility is applied through mid-row banders. He aims to travel at between four to 4.5 miles per hour at seeding. He finds at that speed with narrow knife openers on the drill he sees very little seed bounce.
Gosling, owner of Premium Ag crop consulting, who also farms some of his own land near Strathmore, Alta., says the message from research as well as his own experience tells him that in most cases 1 1/4 inches is a good seeding depth — hopefully getting the seed down and into moisture.
He recalls being asked for advice on one farm visit where an early-, shallow-seeded crop hadn’t done anything. “This farmer had seeded six sections of canola in April, and he called me in June and wanted advice on what he should do,” says Gosling. “It had been a dry spring and the only crop that germinated was in the low, slough bottom areas of the fields. The crop was just starting to flower in slough areas, and over the rest of his acres it hadn’t even germinated. He asked me if he should reseed.”
Gosling said with a weather forecast calling for a chance of rain, he recommended the farmer wait three days to see what happened. “It did rain. The crop finally germinated and grew, and in the end he harvested a 30 bushel per acre crop,” says Gosling. “It wasn’t great but it was better than reseeding. But, he had seeded shallow and with a couple days of drying winds, it dried out. The seed and inputs sat there for nearly three months until it rained.”
Gosling says there are several factors that will determine the success of canola stand establishment that affect seed mortality. Three of the most important in his books include soil quality, seeding date and seeding speed.
The higher the soil organic matter the greater ability it has to hold moisture to help get the crop started.
With seeding date, it may be nice to get the crop seeded by April 10, but the soil is cooler, increasing the risk of seed mortality. If seeding May 10, the soil should be warming up, which helps the crop to germinate and grow vigorously.
Seeding speed also has an impact on seed placement. “If someone is planning to drive eight miles per hour they are better off targeting a one-inch seeding depth because there is going to be a lot of bounce and variation of seed placement with some seed being too shallow and others being too deep,” says Gosling. He recommends seeding at 3.5 to four miles per hour and to aim for a seeding depth of 1 1/4 inches.
“There is always a bit of bounce, but at that speed you will rarely have any seeds placed at two inches deep and rarely have any at a half inch depth,” says Gosling. “The seeds should be into moisture and begin growing.”