A healthy canola crop produces about 50 per cent more flowers than it will use, so days in flower is not a good estimate of yield. To get a better picture of yield potential, look at the early-season leaf density

“You walk into a field that has the spindly plants that don’t have those big basal leaves and you can tell right away

this is a 28-bushel crop.” — PHIL THOMAS

The length of time a canola crop is in flower doesn’t have as much bearing on crop yield as some people believe, says a well-known Canadian expert on canola production.

Most of the pollination that affects seed set and pod production takes place in the first two weeks of flowering, says Phil Thomas, now working as a private consultant after many years as a canola production specialist with Alberta Agriculture.

“If your crop flowers for four weeks or longer, that doesn’t mean you are going to have higher yields,” says Thomas, who is a senior consultant with Agri-Trend Agrology. “I have heard people talk about how each day of flowering means an extra bushel of yield, but that is really just an old wives’ tale. Most of the seed set takes place in the first two weeks and in some circumstances maybe as much as three weeks, but any flowering beyond that has no impact on yield.”

The biggest factors affecting yield goes back to the Canola 101 classroom, says Thomas. “If you get the crop seeded properly and it gets off to a good vigorous, healthy start, and produces a nice uniform stand, that’s what produces maximum yields,” he says.

Seed early, seed into a warm moist seed bed, seed shallow, apply proper fertility, use good quality seed with high germination and plumpness, and seed at the proper rate for optimum plant density. Those are among the key factors for maximizing yield. “It is a matter of looking after the basics, and then if you have good growing conditions, you will have a nice uniform, healthy stand that will produce top yields,” he says. “I have walked canola fields across Western Canada and it is a terrible situation. I am there looking for a diagnosis to a problem and in 10 to 15 per cent of fields the problems are related to mechanical issues. The problems are related to manageable factors created during the physical act of seeding. The seed is too deep, the drill was not set properly, there was too much air, there was too much fertilizer placed with the seed, or there aren’t enough plants in the ground.”

Producers need to go back to square one and pay attention to the long-standing recommendations for getting a crop properly seeded and established.

Thomas, describing canola as a very flexible crop, says the oilseed produces way more flowers than it actually needs. In a good stand, under ideal conditions, about 50 per cent of flowers will be aborted without pollinating or forming pods. “The reason it produces so many flowers is for survival reasons,” says Thomas. “If there is a storm or something that causes a crop to lose half it’s flowers early in the flowering period, it can still crank out a lot of flowers and make up the difference in yield.”

But the crop has a limit when it comes to seed set. Canola has what he calls the “sink source effect.” That means in a healthy canola crop, with good root development, and a large amount of plant biomass above ground, the crop starts flowering, and flowers will be pollinated until the plant gets to the point where enough flowers have been pollinated to match the growth capability of the plant. “The plant starts flowering and then says ‘that’s it I can’t do anymore,’ and then it starts aborting flowers,” says Thomas. “The bulk of seed is determined in that initial thrust of flowering, if conditions are good.”


While there are several important basic factors to establishing a healthy vigorous crop, Thomas says producers need to make sure they have enough seed in the ground. Depending on the quality of seed, how it is handled, and how much fertilizer is placed with the seed, on average only about 50 per cent of seed germinates or survives. Growers who do an “exceptional job” of seed care and handling may trim that to 20 per cent seed loss, but 50 per cent is closer to the average.

Depending on management and growing conditions about the lowest plant density to achieve optimum yields is seven to eight plants per square foot and on the upper end it is in the 10 to 12 plants per square foot range.

How do you determine that? It begins with using the 1,000 kernel weight formula to determine seeding rate, he says. “Generally we have very good quality seed available to growers in Western Canada,” he says. “But among the different varieties there can be tremendous variation in the seed size and weight of seed lots.” He has found some seed varieties weigh out at 2.5 grams per 1,000 kernels, while another will weigh 6.5 grams per 1,000 kernels. “When you have that kind of variation depending on what variety you are growing, how can a blanket 4.5 or 5.5 pounds per acre seeding rate give you the number of plants you need?” he says.

Thomas recommends farmers use the 1,000 kernel weight formula to determine seeding rate and then actually go out and do plant counts to determine the number of plants that survived.

“Here is the seeding rate I used based on the 1,000 kernel weight formula, so what is my seed mortality rate,” he says. “Go out and count the number of plants per square foot. Determine if seed mortality rate was 20 per cent, 30 per cent, 40 per cent or higher and do that for three of four years and then you will be able to determine a seed mortality based on your seeding practices.” From there, you can start to make improvements, if necessary.

A proper plant density, with all other good production practices in place sets the stage for optimizing yields. “The objective is to have a crop with a good photosynthetic base,” says Thomas. “You want a crop that achieves a large leaf-area index early. These plants are about a foot high and they have these large leaves early in the growing season. That tells me the crop has the photosynthetic manufacturing base to achieve high yields. And if you don’t have that large leaf-area index early, forget it, because the crop can’t make up for it later on.

“The difference is that you walk into a field that has the spindly plants that don’t have those big basal leaves and you can tell right away this is a 28-bushel crop. And then you go to the next field with a crop with big leaves that has the high photosynthetic ability to make food and it has the yield capability for a 50-or 55-bushel crop.”

Lee Hart is editor of Cattlemen’s Corner. He can be reached at 403-592-1964 or by email at [email protected]

About the author

Field Editor

Lee Hart

Lee Hart is editor of Cattleman’s Corner based in Calgary.



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