Spring and Winter Canola:
Planting and Crop Development
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811: Agronomy Guide > Spring
and Winter Canola > Planting and Crop Development
Order OMAFRA Publication
811: Agronomy Guide for Field Crops
-
Seed Quality
Know the quality of the seed being planted. Germination is the
major quality consideration used in grading seedlots. Germination
standards test the ability of a seedlot to produce normal seedlings
under favourable conditions of 95%-100% humidity and 25°C. Stress
conditions in the field following planting often reduce field emergence
compared to lab results. Certified seed must meet purity and germination
standards.
Seed Treatments
Certified seed is treated with a fungicide and insecticide. The
fungicide controls seed-borne and early-season soil-borne diseases,
including blackleg, seed decay, damping-off and seedling blight.
Insecticide seed treatments contol flea beetles for 2-4 weeks. Slow
seedling development may allow flea beetle populations to build
after the effectiveness of the seed treatement has declined, requiring
a follow-up foliar insecticide treatment (see OMAFRA
Publication 812, Field Crop Protection Guide).
Spring Canola Seeding Date
Typically, early seeding produces the highest yields. In recent
years, some growers report good yields from seeding in mid-May.
Consider, though, that flowering generally begins 50-55 days after
planting and lasts 10-21 days. Temperature stress (>28°C)
during flowering has a greater negative impact on yield than weather
at any other stage.
Early Seeding
Seed as early as soil conditions permit. Canola will germinate
and grow at a soil temperatures of 1°C, but 10°C is ideal
for rapid emergence. Soil conditions and weather forecasts should
be the ultimate guide, however 3°C or higher is a reasonable
target for planting. Increase seeding rates by 5%-10% when canola
is planted very early to account for slower emergence and increased
seedling mortality. Canola is slower to establish than cereal crops
and is less tolerant to spring frost. When seedlings emerge, the
growing point is exposed between the cotyledon (seed) leaves and
can be easily killed by a frost. Early planted canola also has a
higher risk of infestation by cabbage seedpod weevil during the
flowering/early pod stage. If canola growth is slow following planting
due to cold weather, flea beatles may become a problem.
Late Seeding
If seeding is delayed, it is critical to conserve soil moisture
and to plant into moisture for rapid, uniform emergence. Avoid seeding
after June 1st in areas where swede midge has been identified. See
Swede midge
or visit the OMAFRA website at www.ontario.ca/crops.
Table 6-1. Amount of Seed Required
to Meet Target Seeding Rate
1,000-Seed Weight
(gm) |
Target Seeding Rate1
kg/ha (lb/acre) |
Seeds
/m1(/ft) |
|
3.5
|
3.63 (3.3)
|
20 (6.1)
|
|
4.0
|
3.63 (3.3)
|
20 (6.1)
|
|
4.5
|
4.7 (4.2)
|
20 (6.1)
|
|
5.0
|
5.2 (4.7)
|
20 (6.1)
|
|
5.5
|
5.7 (5.1)
|
20 (6.1)
|
|
6.0
|
6.2 (5.6)
|
20 (6.1)
|
Winter Canola Seeding Date
Seed winter canola August 15-30 (in Southwestern Ontario, August
20-September 10). Seeding within these dates results in the canola
developing 4-6 leaves and an adequate size root system (approximately
1 1/4 cm or 1/2 in. diameter) to reduce the chances of frost heaving
and desiccation in the spring. Delays beyond these dates greatly
increase the risk of winterkill. If canola bolts in the fall, it
will not survive through winter. Heavy competition from weeds or
volunteer cereals in the fall can force canola growth, increasing
chances of winterkill.
Seeding Rate
The optimum plant stand for canola is 75-130 plants/m2
(7-12 plants/ft2). In 19-cm (7.5-in.) rows, this is equivalent
to 14-25 plants/m (4.5-7.5 plants/ft) of row. Target seeding rates
need to account for large differences in seed size between varieties.
Table 6-1, Amount of Seed Required to Meet Target
Seeding Rate, presents the desired seeding rate for different
seed sizes. Increase seeding rates slightly (5%-10%) on soils prone
to crusting, when seeding very early or very late.
Seed Bulking
Achieving target canola seeding rates can be a challenge with some
drills. Calibrate seeding equipment before heading to the field.
Ensure that each of the drill's seed cup openings are set the same.
Bulking of seed with pelletized MAP (11-52-0), sulphur or corn cob
grits are options for improving seeding rate accuracy. Do not use
other fertilizers with canola seed, as this increases the risk of
reduced seed germination.
Seeding Depth
Canola seedlings expend a great deal of energy to emerge, making
quick, even emergence the goal in seeding. Seed 1.25-2.5 cm (1/2-1
in.) deep, if there is adequate moisture, and deeper if necessary
to plant 0.6 cm (1/4 in.) into moisture, but not deeper than 4 cm
(1 1/2 in.). If the depth to reach moisture is deeper, it is better
to wait for moisture. Press wheels on the drill help place the seed
uniformly at the bottom of the seed trench. Drill bounce is more
of a problem at speeds over 8 km/hr. Increasing speed affects planting
depth. If canola is seeded through the grass seed box, seed tubes
should be directed behind openers and in front of the press wheels.
Seeding Rate
The seeding rate can be determined by knowing the 1,000-seed weight
in grams found on the seed tag and using the following formula:
Metric
Seeding rate (kg/ha) = (desired plant population/m² x 1,000-seed
wt. (gm) ÷ seedling survival rate) ÷ 100
Imperial
Seeding rate (lb/acre) = (desired plant population/ft² x 1,000-seed
wt. ÷ seedling survival rate) ÷ 10.4
Seedling survival (final stand) = % germination (on seed tag) x
% expected emergence
Sample Calculation
Using seed size of 5 gm/1,000 seeds, 72% final stand
Seeding Rate (lb/acre)
= (7 plants/ft² x 5 gm/1,000 ÷ 0.72) ÷ 10.4
= 4.7 lb/acre
Seed Drill Calibration
Collect and weigh (in grams) the seed from a drill opener and use
the following formula to convert to lb of seed/acre using a 7.5
in. row width. Check several openers.
Seeding rate (lb/acre) = gm of seed/opener/30.5 m (100 ft) of travel
x 1.54
Seeding Conditions
Good seedbed preparation is vital, due to canola's small seed size
and shallow planting depth requirements. The seedbed should be level,
firm, and crumbly with moisture in the top 2.5 cm (1 in.) of the
surface. A crumbly soil will resist crusting after pounding rains,
allowing the tiny seedlings to emerge. This is critical, since there
is no opportunity to correct crusting. The crust can break the hypocotyl
arch (the seedling stem) that lifts the cotyledons (seed leaves)
above the soil surface. A firm seedbed will help hold moisture near
the surface and aid in uniform planting depth and uniform emergence.
Packing
Let soil conditions determine whether to pack the seedbed before
or after seeding. Packing before seeding can help level and firm
the seedbed, improving seeding depth control and reducing soil moisture
loss. Packing after planting can improve emergence and yield, if
the soil dries out before emergence. Packing after seeding may bury
the seed deeper if the field was ridged at seeding, thereby reducing
emergence.
Broadcast Seeding
Broadcasting of canola seed is a greater risk than seeding with
a drill but can still be effective in some situations. Some growers
broadcast canola seed with fertilizer onto a prepared seedbed. The
advantages of broadcast seeding are higher yield potential because
of early seeding date, time savings and low cost. The major disadvantage
of broadcast seeding is uneven planting depth and uneven seed application
(if uncalibrated). Frost injury is also a risk with an early seeding
date. Good seedbed preparation before broadcasting followed by harrowing
or packing will keep seed depth constant and ensure good seed-to-soil
contact. Despite this, broadcast stands can be inconsistent in dry
years. Seeding rates should be higher when broadcast compared to
drilled (6-8 kg/ha or 5-7 lb/acre).
Replant Decisions
Generally, canola plants in thin stands will branch out aggressively
to compensate, resulting in no significant yield loss. Each year,
some fields suffer from thin stands due to poor emergence, frost,
insects and diseases. To make a decision, assess the health and
plant population of the surviving stand. It is easy to overestimate
the extent of the injury and underestimate the ability of seedlings
to recover. A uniform stand of 11-22 healthy plants/m2
(1-2 plants/ft2) will have a yield that is 90% of a full
stand. Assess populations using the hula hoop method to determine
plant populations (see Appendix K, Hula Hoop Method for Determining
Plant and Pest Populations, on page 268).
Plant Development
Spring canola is a cool-season crop that grows best at temperatures
above 10°C and below 30°C (optimum 20°C - 25°C).
Crop development is closely related to the amount of sunshine received,
although temperature also is a factor.
Table 6-2. Approximate Growing Degree
Days to Reach Various Stages of Development
Growth Stage
(decimal code system) |
Description |
Growing Degree Days
(Base 0ºC)1 |
|
0-1.0
|
Emergence
|
152-86
|
|
1.1-1.2
|
1-2 leaf stage
|
282-324
|
|
1.4-1.6
|
4-6 leaf stage
|
411-463
|
|
3.0-4.0
|
Bud-first flower
|
582-666
|
|
4.9
|
Late flower
|
759-852
|
|
8.1
|
Maturity2
|
1,432-1,557
|
1Adapted using research data from AAFC, Scott and Swift
Current.
2Occurs when seed begins to mature, 10% seed colour change.
Development of canola is more closely aligned with growing degree
days than crop heat units, similar to that of spring wheat. Canola
matures in approximately 90-100 days in southern growing areas,
and 110-120 days at New Liskeard. In northern growing regions, longer
day length can partly compensate for lower temperatures. Drought
and heat stress will shorten the days to reach maturity. The approximate
GDDs to reach various stages of development is presented in Table
6-2, Approximate Growing Degree Days to Reach Various Stages of
Development. High temperatures at flowering cause flower and
pod abortion. Maturity differences among varieties is typically
less than 7 days.
Principal Growth Stages of Canola
Rosette
Germination of canola is similar to other dicots - seedlings emerge
with the growing point contained between cotyledons (seed leaves).
A 5-6-leaf rosette forms, with larger, older leaves at the base
and smaller, younger leaves developing in the centre. Leaf area
development is directly related to growth rate and final yield.
Stem Elongation (Bolting)
Lengthening days and rising temperatures trigger bud formation
in the centre of the rosette and the stem rapidly "bolts".
The main stem reaches 30%-60% of its final height at the start of
flowering. A large leaf area (especially upper leaves) at this stage
strongly influences pod set and final yield.
Flower
Flowering begins with the opening of the lowest bud on the main
stem and continues upward on both main and secondary branches. Flowering
continues for about 14-21 days.
Table 6-3. Nitrogen Recommendations
for Spring Canola
N:Canola Price Ratio
($/kg N:$/kg canola)
|
Recommended N Rate
(kg/ha) |
|
2
|
119
|
|
2.5
|
108
|
|
3
|
96
|
|
3.3
|
90
|
|
3.5
|
85
|
|
4
|
74
|
100 kg/ha = 90 lb/acre
To use this table, the price of canola must be known or estimated.
Canola at $450/t and nitrogen at $1.50/kg results in a price ratio
of 3.3 (1.50/0.45). At these prices, use 90 kg/ha of nitrogen.
Fertilization occurs within 24 hours of pollination. The maximum
plant height is reached at peak flowering. Typically, flowering
begins 50-55 days after planting (582-666 GDD). Temperature stress
(>28°C) during flowering causes flower abortion and is detrimental
to yield at this stage (Plate 33). Canola
can either self-pollinate or cross-pollinate, depending on various
environmental factors.
Plate
33. Heat blast. Hot temperatures during flowering (especially spring
varieties) can cause heat blast and reduce seed yields.
Ripening
The leaf, stem and especially pod surface area are major food sources
for the developing seed. Seed filling is complete about 30-40 days
after flower opening. Pod ripening occurs from bottom to top of
the plant. When seeds have turned green, leaf senescence begins,
and the pod wall becomes the major source of food, although the
stem is also important. When 30%-40% of seeds on a plant have started
to change colour, seed at the top of plant will be nearly mature,
and the average seed moisture will be 30%-35%.
