Canola growth is characterized
by six main growth stages.
I. Pre-emergence stage:
The germinating seedling may
take from 4 to 10 days to emerge. During this time it is susceptible to many
soil borne pathogens therefore seed treatment is necessary.
II. Seedling Stage:
In this stage the seedling very
young plant has just emerged from the soil. Cotyledons are pushed through the
soil surface by an active hypocotyl. At this stage, the seedling is still
vulnerable to many soil pathogens, and to flea beetle infestation.
III. Rosette stage:
This stage is the rosette stage
characterized by an increasing leaf area index. Spring canola will remain in
this vegetative stage for several weeks. Winter canola also stays in this stage
for several weeks in the spring. Near the end of Stage 3, the crop is nearing
its maximum leaf area index and at that point is a much better competitor.
IV. Budding stage:
Increasing day length and
temperatures initiate bolting and the beginning of the bud stage. The plants
reach their maximum leaf area index at this time along with 30 to 60% of its
total dry matter. A large accumulation of foliage is required to provide
adequate sugars during flowering and pod fill.
V. Flowering stage begins and continues for 14 to 21 days. Three to five
flowers open per day and 40 to 55% of the flowers that open will develop pods.
VI. Ripening stage begins when the petals fall from the last formed flower on
the main stem. Pod fill is complete 35 to 45 days after flower initiation, and
the seeds contain about 40% moisture at this point. The crop is considered ripe
and ready for swathing when 30 to 40% of the seed from pods on the main stem
have turned color.
CLIMATE
Rapeseed and mustard crops are
grown in tropical and temperate zones. These grow well from an altitude of 650
– 1500 meters. A warm weather (20°C) during seed germination, 15°C – 20°C
during plant growth and long sunny bright days (25°C – 27°C) at flowering and
pod formation are most suitable for these crops. Rapeseed and Mustard grow best
under relatively cool temperatures upto flowering. These crops grow profusely
at 30 – 60% relative humidity. Toria is hardy plant, grows in comparatively
warmer and dry season. Among rape and mustard crops, sarson is the most susceptible
to frost injury whereas; Rai and taramira are more tolerant to extreme weather
condition.
SOIL
Rapeseed-mustard can be grown on
a wide range of soils including both light and heavy soils. Crop can tolerate a
variable range of pH from 5.5 to 8.0. However, the most suitable soils are
those that are:
- Deep
and free from hardpan, allow good taproot development, uniformly textured,
allow even establishment.
- Unlikely
to crust after rain, so that the seedling can emerge easily.
- Not
prompt to water logging, rapeseed will tolerate winter water logging. This
applies especially to Brassica campestris.
- Not
Acidic with high aluminum and manganese levels.
LAND PREPARATION
Rapeseed and mustard crops
require a field with proper capillary action, that encourages the movement of
water from sub-soil to top-soil and mulching that prevents water loss to the
atmosphere. Field preparation depends upon the kind of soil, previous crop and
more on intensity of weeds. Sandy loam soils are easy to prepare but require
much labour in reducing the menace of some perennial grasses. This requires a
comprehensive, deep ploughing, harrowing, collection of stubbles of these
grasses and finally planking to conserve the soil moisture. The land is
repeatedly ploughed with soil turning plough followed by cross harrowings and
planking during cool hours, preferably during night or very early hours of the day.
A clean and well pulverized seedbed of good tilth is prepared.
SEED RATE
Yields are not affected
significantly due to varied plant densities. Moderate adjustments in seed rate
have little effect on yield. Thin crop stand compensate by extra branching.
However, recommended seeding rates are 1.5 to 2.0 kg/acre.
- Lower than normal seed rate will help to reduce
lodging and harvest.
- Seed rate above 2.5 kg/acre will result in tall
spindly plants prone to lodging.
- Increased seed rate suppresses weed infestation. It
has been observed that dense crop stand discourages too many branching and
crop matures more uniformly which facilitate combining.
SOWING TIME
Canola, Rapeseed and mustard are
highly photo-sensitive crops. Sowing early or late, both have been reported to
be harmful. Loss in yield, due to delayed sowing cannot be compensated by
higher seed rate or higher doses of fertilizers. The planting schedule for
different areas is as follows:
- KPK:
Mid-September to mid-October
- Sindh:
Mid-October to mid-November
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