Spring and Winter Canola: Planting
and Crop Development
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Pub 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%.
