Important Tips For Best Management
Early-seeded canola crops tend to produce higher yield and quality. These crops tend to flower before peak summer heat, which can lead to flower blast and pod abortion, and maturing earlier often helps mitigate damage from frost in the fall or other stresses that cause premature senescence.
Cold soil temperatures following seeding can delay emergence and increase seedling mortality, sometimes offsetting the benefits of earlier planting. Canola seeded into 2 °C soils can germinate, but may take up to 3 weeks to reach 50% emergence if temperatures remain cool. Waiting for somewhat warmer soils may allow establishment of a denser more uniform stand that matures more evenly and can be harvested earlier, but consider the calendar and long range forecast. Soil temperatures of 5 °C or higher with warmer weather in the forecast should facilitate reasonably good rates of emergence, but from the second week of May onward growers should probably take advantage of good field conditions for seeding regardless of temperatures.
Because canola emerges more slowly in cold soils, protection from seed treatments may decline before the crop has outgrown its most susceptible phase. With early seeded canola, be ready to apply an insecticide to control early season flea beetles. Earlier control of weeds may also be necessary, especially for perennials and winter annuals that are better adapted for growing under cold conditions.
Seeding into cold soils increases the need for management techniques that reduce stress on emerging seedlings such as seeding shallow, some seed placed phosphate to get the “pop up effect,” uniform seed placement, early weed control, and proper crop residue management to allow the soil to warm as quickly as possible. Growers may want to increase seeding rate to offset the potential for lower seed survival in cool soils.
Yield trends
The yield advantage for early seeding — with all else being equal — can be significant.Seeding early, providing that crop conditions allow for it, is a relatively low cost way to increase yield and profit from the crop.
In general, “early” seeding occurs from late April to mid May but varies by region. In the southern Prairies, early seeding usually allows the crop to utilize winter and early spring moisture more effectively and may help the crop avoid the highest summer temperatures during flowering. Early season moisture from snow melt can be critical to facilitate the shallow seed placement required for maximum emergence and good seedling establishment and growth. Missing this early season moisture forces the crop to rely more heavily on subsequent rains throughout the season.
Optimum canola seeding dates in Ontario are usually in late April to early May — slightly earlier than western Canada. Significant yield reductions occur if seeding is delayed after mid-May, mostly because the crop is flowering during the hot and frequently dry weather in late June and July.
By seeding some fields early, this maximizes the amount of acres seeded in the proper seeding date window — rather than having a large amount of acres seeded at the end of the seeding window. In most areas in western Canada, seeding after the third week of May puts canola at higher risk for fall frost losses.
Early seeding increases the risk of stand loss due to lethal spring frosts, but canola seedlings that are slow growing and have hardened off can withstand some early season frost. Early seeding can decrease the risk of yield and quality loss due to fall frost damage. Seeding early may actually reduce the overall frost risk since spring stands severely damaged by frost still have ample time to recover or to be reseeded.
If soil temperatures are cold during seeding, then other seeding practices (treated seed, pedigreed seed, good seed-soil contact, proper fertilizer placement, correct seeding depth and rate) become even more important.
Keep in mind that canola emerges more slowly in cold soils, which means protection provided by seed treatments can decline before the crop has outgrown its most susceptible phase. With early seeded canola, be ready to apply an insecticide to control early season flea beetles. Slow growing canola crops will also be more vulnerable at the seedling stage to weed competition. Earlier control of weeds may be necessary, especially for perennials and winter annuals that are better adapted for growing under cold conditions, and hence more able to compete with the crop under those conditions.
Seeding date is often dictated by factors outside the grower’s control. These include:
The field has to be able to support tractor traffic. This depends on the amount of snow and runoff, soil texture, spring precipitation and temperature, slope, and residue. As well, the field has to be dry enough to ensure the canola is not “mudded in”. The field may support the tractor and drill, but soil does not fill in properly over the furrow and packers mud up and slide. Seed placement and seed to soil contact suffer, resulting in inconsistent seed depth and uneven emergence.
Pre-seed herbicide applications to control winter annuals and cool-season weeds may push back seeding dates, especially since growers want to make sure weather is warm to ensure good herbicide uptake. When seeding without pre-seed weed control, a post seeding/pre-emergent or early in-crop application will be necessary.
Source: Canolacouncil