Planting date is one of the most important and manageable agronomic practices that affect growth, dry matter production, quality and yield potential of canola.¹ Canola consists of three species: Brassica napus, known as Argentine canola; B. rapa, known as Polish Canola; and B. juncea, known as brown mustard. B. napus is the most widely grown species of canola in Canada and is the focus of this article (Figure 1).

In canola, seeding date plays a crucial role in harvest timing and yield quality. Early-seeded canola crops can have higher yield potential and quality. Early maturing canola products, including products offered by DEKALB^®, that are planted early can flower before the high temperatures of July, reducing the potential for damage to flowers and related yield losses. Canola that matures earlier in the fall can also help mitigate damage from frost or other stresses that cause premature death and quality downgrading.²

Timing of Canola Seeding

Seeding date decisions for canola are often driven by historical frost risk than present conditions. This is why many growers wait to seed canola until after May 1, even if their area had what seemed like favorable seeding conditions in April.

Canola is planted in May and harvested in September or October in the Northern United States and Canada. Seeding canola as soon as possible in the spring increases the likelihood of optimizing canola yield potential and quality compared to traditional spring seeding dates.³ A study conducted at the Saskatchewan Canola Development Commission (SCDC), documented that plots seeded prior to May 20th resulted in higher seedling establishment, canola biomass and seed yield compared to those seeded on June 3rd.⁴

Early planting dates can help enable the crop to take advantage of good spring moisture, avoid some heat stress at flowering, and reduce the risk of fall frost damage. Delayed planting can result in shortened vegetative and flowering duration, which is the main cause for the decline in above ground dry matter production which can lead to lower seed yield.⁵

Monitor soil temperatures prior to planting. Soil temperatures below 8 to 10^°C can result in progressively poorer germination and emergence.⁶ Canola seeded in late April can face higher risks of damage from early insect infestations, seedling disease, water ponding, soil crusting, and frost. However, with the right conditions, seeding in late April can provide higher yield potential over May seeding.⁷ April-seeded canola is likely to have higher seedling mortality but the plants that survive should have more time to branch out and compensate for a thinner stand (https://www.canolacouncil.org/).²

In general, Manitoba and Eastern Saskatchewan have a lower percentage of canola seeded than other parts of the prairie. Canola seeded June 5th or even June 10th in those regions can produce a good crop, and crop insurance deadlines are a reflection of that. In Manitoba, the deadline for full crop insurance coverage for Argentine canola is June 15^th for the south and June 10 for the north. The extended seeding period (20% reduced coverage) is June 16^th through June 20^th for the south and June 11^th through June 15^th for the north. The general crop insurance deadline for Saskatchewan is to have crops seeded by June 20^th; however, the deadline for canola seeding differs by rural municipality and variety. In Alberta, the recommended seeding date for canola is May 31. Canola seeded later than the recommended seeding date may not qualify for grade loss coverage.

In Alberta, AFSC has extended its recommended seeding date deadlines for yield and quality coverage to June 5 for Argentine canola and June 15 for Polish canola. The original deadline was May 31. However, yield-only insurance deadline is still June 20. For seeding deadlines in Saskatchewan contact your local SCIC office. For Manitoba, seeding deadline are June 15 for Argentine canola in risk area 1, June 10 for Argentine canola in risk area 2 and June 20 for Polish variety. Contact your local insurance provider for more information.

Not all canola can be seeded during the first weeks of May due to crop conditions or farm operation logistics. With late May or early June seeding, the risk of flower blast due to summer heat and fall frost prematurely halting maturity increases. However, with favorable conditions, late May or early June seeded canola can have adequate yield potential and quality. Later seeding tends to reduce the estimated days to maturity for a canola variety as documented by research from Edmonton, Alberta and Brandon, Manitoba (Table 1). This reduction in maturity is often about half of the delay in seeding. For example, if seeding is 14 days later than optimal, a variety rated to mature in 100 days may mature in 93 days.

Maturity differences between canola products narrow as you get into warmer climates. In southern Manitoba, seeding dates that are later into May and June have fewer total days required to mature. For example, a canola product rated at 100 days to maturity may only take 95 days to mature if seeded at the end of May. This is due to more rapid accumulation of heat units in warmer days. Seeding in June may reduce time to maturity by five to 10 days.

Canola Product Selection

Selecting a canola product is one of the most important decisions a grower makes for a successful crop. The performance of a canola product can differ from year to year and location to location due to changing environmental conditions. Factors to consider when selecting canola products include:

• Yield– Select products with consistent high yield potential.
• Plant height and lodging– These factors are important to consider making swathing easier as well as helping to reduce disease incidence.
• Disease tolerance– Select products with good resistance to blackleg. Products with superior lodging resistance can help reduce the incidence of Sclerotinia stem rot.
• Seedling vigor– Products with good seedling vigor can be more competitive with weeds and more likely to push through a shallow crust.⁸
• Maturity– Select an earlier-maturing variety. Switching from a long-season to an early-season variety can help lower the risk of fall frost.

The Canola Performance Trials, found at https://www.canolaperformancetrials.ca/ can help with identifying earlier-maturing canola varieties, as well as yield performance and disease resistance. For local trial results see https://www.cropscience.bayer.ca/en/Products/DEKALB-Seed/Trial-Map or check with your local Bayer representative.

• To manage harvest timing and environmental risks, consider selecting more than one canola variety with different maturities. Seeding early-maturing varieties first and long-season varieties last can help spread out the harvest workload. Different maturity timing helps to reduce the risk of an environmental factor impacting the total canola crop.

Canola Harvest Timing

Timely harvest of canola is critical to help prevent shattering. When pods first begin to yellow, the crop should be checked every three to four days. Harvest maturity can be calculated by observing the seed color. In canola that stands well, 30 to 40% of the seed on the main stem should be brownish-red in color prior to swathing. This corresponds to about 30 to 35% seed moisture. Canola can lodge, particularly with over-fertilization of susceptible varieties. In severely lodged canola, swathing should be done when 40 to 50% of the seed in exposed pods has turned color. Shattering can account for substantial crop losses, therefore harvesting must not be delayed. Canola that is to be stored for six months or more must be dried to near 8% moisture.⁹

Canola varieties with the pod-shatter tolerance trait can be a good fit for straight cutting canola, as these fields may be able to stay in the field longer than a swathed field to reach full maturity. Pay additional attention to conditioning straight cut canola (and getting it down to 10% moisture or less), especially if it has some high moisture dockage mixed in. There are many aspects to consider for straight cutting a canola crop, such as a well-knit crop with uniform maturity and low disease. Follow the labels for appropriate application timing of desiccants. Harvest as soon as possible after the seed falls below 2% green content and is dry enough to store. Delayed harvest can increase shattering losses. Consider adjusting header reel and knife position, speed settings, cylinder speed, travel speed of combine, and fan speed which may help reduce shattering losses. Aerate straight-combined canola for at least a day or two after combining.

Summary

Seeding canola early increases the likelihood of optimizing canola yield potential and quality. Early planting dates can help enable the crop to take advantage of good spring moisture, avoid some heat stress at flowering, and reduce the risk of fall frost damage. Delayed planting can result in lower seed yield. Seeding early canola varieties first and long-season varieties last can help spread out the harvest workload and reduce risk of harvest loses.