Hiking canola yields starts with plant density

Seeding rate and survivability are the two factors growers must pay attention to when working to maximize production

Canadian farmers are expected to increase canola plantings by 4.4 percent this spring, according to Agriculture Canada’s latest Outlook for Principal Field Crops report.

Amid tightening domestic supplies and record prices for near-term futures contracts, 2021-22 canola plantings are forecast to jump to nearly 22 million acres this spring and total production is expected to rise eight percent to 20.2 million tonnes, the third-largest canola crop ever produced in the country, the Feb. 17 report said.

Despite that, total canola supplies in the 2021-22 crop year are expected to tighten further to 21 million tonnes, based on an expectation of continued selling and a sharp drop in carry-over stocks come August.

With those market fundamentals in mind, growers this spring may seed more canola acres and seek ways to maximize production.

Shawn Senko, an agronomy specialist with the Canola Council of Canada, said efforts to maximize canola yields start with calculating an appropriate seeding rate and targeting plant densities that allow a field to reach its maximum yield potential.

“In the past, the focus has always been on pounds per acre and how (heavy) you’re going to seed but we really want to get to that target plant density instead,” Senko said.

“We say five to eight plants per sq. foot is ideal so when you’re thinking of seeding, you should make sure you’re actually shooting for a target plant density in that range.”

However, achieving optimal plant density is not an exact science because of unpredictable environmental conditions.

In general, however, plant density can be viewed as a function of two factors: seeding rate and survivability.

Growers should start by observing their seed lot’s thousand seed weight (TSW), which should be listed on the seed bag.

Survivability refers to the percentage of seeds sown that produce a viable canola plant.

Survivability depends on a variety of environmental conditions, including soil temperature, seeding depth, fertilizer placement and frost risk, among others.

In general, however, it can safely be assumed that a properly managed field will have a survivability rate in the range of 50 to 60 percent.

The canola council has developed a series of online calculators that can be used to calculate seeding rates, target plant densities and harvest losses.

The calculators are located at www.canolacouncil.org/calculator/.

“The seeding rate calculator makes it easy,” Senko said. “You just put in your TSW, your target plant density and your expected survivability and it will put out a seeding rate based on that information.”

Although the canola industry assumes a typical survivability rate of 50 to 60 percent, producers can monitor their own annual survivability rates by counting plant densities in the field.

In the spring, densities should be determined by counting plants at the two-to-four leaf stage in different parts of the field, typically about three weeks after the crop has been planted.

Plant densities on a per-sq.-foot basis can also be taken post-harvest by counting stems in undisturbed stubble.

Densities observed should be recorded for future reference.

Historical record keeping can be useful in determining average survivability rates on individual fields or across an entire farm. However, growers should keep in mind that unusual environmental factors in any given spring can have a significant impact on survivability that year and can skew multi-year averages.

“Typically, we say survivability should be around that 60 percent mark … but we do want producers going out and actually doing their own assessments after seeding, once plant emerge…,” Senko said.

“It’ll change from year to year but it will give you a good idea of what you’re actually capable of with the equipment you’re using.”

Senko said optimal plant densities in the five to eight plant range should give growers an opportunity to reach their optimal yield potential.

Plant densities below five can be expected to produce smaller yields, although plant densities as low as three can produce yields that are sub-optimal yet acceptable.

“On the low end, there’s a bit of a buffer in there but once you get down below three plants per sq. foot, that’s where you start to see issues of not being able to achieve that maximum yield potential any more,” he said.

Weed competition in a thin plant stand will typically be higher and optimal utilization of soil moisture and nutrients by the cultivated crop will be compromised.

Stand density, which is normally established within two to three weeks of seeding, will affect everything else through the growing season, from weed control to uniformity, evenness of maturity and ease of harvestability.

On the high end, plant densities above eight plants per sq. foot typically won’t result in a reduced yield but they do imply that production costs could have been lowered had the grower selected a more appropriate and less expensive seeding rate.

“There’s no yield affect once you get past the top end (of eight plants per sq. foot),” Senko said.

After that, “the yield curve is pretty flat.”

Senko said the reproductive nature of canola rests on the plant’s ability to produce a high number of seeds per plant.

Heavy seed production compensates for the plant’s low survivability rates, relative to larger seeded crops such as corn or soybeans.

“Canola survivability is definitely improving over time,” Senko said.

“The 50 to 60 percent survivability is based on the information that we have right now but we’re hoping that with proper management, we’ll start to see that increase over time.”

Senko said the canola council plans to launch a new canola plant stand survey this year in hopes of getting a better read on average plant stand emergence.

With improvements in management practices, equipment and seed genetics, growers across the West could achieve average survivability rates in excess of 60 percent.

“We’ll be launching the survey online and… it will be (encouraging) producers and agronomists to enter their data…,” Senko said.

“It should give us a more accurate idea of what we’re getting for survivability and also anybody who enters their data will get to see the average in their area and look at how their data compared to (other growers’) in the area.”

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