Mustard is the third most
important source of edible oil after cotton and sunflower in Pakistan
Rapeseed is well adapted
in temperate region and requires cool temperature for vegetative and
reproductive growth. The growth cycle of rapeseed may be as short as 95 days or
long as 160 days. Rapeseed and Mustard grow best under relatively cool
temperatures upto flowering. After flowering they can tolerate high
temperature, however, more heat and drought stress may result in a reduction of
seed size, crop yield and oil contents. Among rape and mustard crops, sarsoon
is the most susceptible to frost injury whereas; raya and taramira are more
tolerant to extreme weather condition. Rapeseed-mustard can be grown on a wide
range of soils including both light and heavy type. Crop can tolerate a
variable range of pH from 5.5 to 8.0. However, the most suitable soils are
those that are:
1.
Deep
and free from hardpan, allow good taproot development, uniformly textured,
allow even establishment.
2.
Unlikely
to crust after rain, so that the seedling can emerge easily.
3. Not
prompt to water logging, rapeseed will tolerate winter water logging. This
applies especially to B. campestris.
4.
Not
Acidic with high aluminum and manganese levels.
Brassica seed must be
placed into a firm, moist warm aerated, well-structured seedbed for rapid
germination and seedling growth. A good seedbed for rape and mustard should be
reasonably leveled, well packed, slightly lumpy and moist within 2-5 cm of the
surface. A loose seedbed with large lumps dries out quickly and affects
germination adversely. A very fine seedbed is also not suitable, as heavy rains
followed by drought may result in crust formation and impede emergence. A
comparatively moist seedbed is desired for zaid Kharif crop to obtain a good
germination. Wet soils should be avoided. Rapeseed can be established successfully
using direct drilling and zero tillage. For optimum seed bed preparation one
mould board plough 30-40 days before planting is required to preserve moisture.
At the time of planting 2-3 times cultivator followed by planking is sufficient
for seed bed preparation.
Sowing Timing is influenced
by soil, variety/hybrid and temperature
and moisture level. The planting schedule for different areas is as follows:
1.
Khyber
Pakhtoon Kha : Mid-September to mid October
2.
Punjab : 1st October to 30 November
3.
South
Punjab : Mid-October to mid
November
4.
Sindh:
Mid-October to mid November
5.
Balochistan:
Mid-October to mid November
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 rate is 1.5 to 2.0 kg/acre.
1.
Lower
than normal seed rate will help to reduce lodging and harvest.
2.
Seed
rate above 2 kg/acre will result in tall spindly plants prone to lodging.
3.
Increased
seed rate suppresses weed infestation. At PBG, UAF it has been observed that
dense crop stand discourages too many branching and crop matures more uniformly
which facilitate combining.
To obtain higher yield and
better crop management, rapeseed-mustard should be grown in rows. Optimum row
spacing is 30 to 45 cm through a grain box of standard wheat sowing equipment
by doing required adjustments for row spacing and placement of seed at uniform
depth. The seed box on modern machines can be calibrated to the recommended low
seed rate. If this is not possible, mix seed with the fertilizer, seed mixed in
this way will only be in contact with the fertilizer for a short period and
germination will not be affected. Use this technique with phosphorus fertilizer
only, as those compounds containing nitrogen may affect germination.
Soil temperature and the
availability of surface moisture will also influence sowing depth. Drill seed
into moist soil to an even, shallow depth of 2 to 4 cm, although seeds are
small, the seedlings grow vigorously and will normally germinate
satisfactorily. Deeper sowing will result in poor emergence, especially in
tight soils. Early in the season sow seeds deeper than 4 cm if necessary, as
temperatures are higher and the seedbed will dry out more rapidly and possible
deeper. Soil fertility is one of the key manageable factors among all the crop
production factors in rapeseed production. Nutrient balance is extremely
important for getting higher yields of rapeseed.
Once nitrogen is taken up
by the plant roots, it moves freely within the plants where it becomes a
constituent of protein and other cellular compounds such as chlorophyll.
Rapeseed responds strongly to nitrogen fertilizer on deficient soils. Results
of field experiments have shown that satisfactory and profitable yields of
rapeseed can be produced on stubble land or in a Continuous cropping system
with adequate fertilizer nitrogen and effective weed control. Under dry land
conditions, profitable yield increases have been obtained in stubble field
experiments, under good moisture, with rates of nitrogen up to 28 kg acre-1.
Crop responses to fertilizer nitrogen are influenced by soil type, moisture
conditions and nutrient balance. High rates should only be applied when a soil
test indicates they are needed. Nitrogen applied to a summer fallow field with
higher available nitrogen content is not justified and may cause delayed
maturity, the response generally does not justify the expense.
The phosphorus
requirements for good yields of rapeseed are equal to nitrogen (28kg/acre).
Rapeseed takes up phosphorus from the soil rapidly in the early growth stages
and continues to remove phosphorus over a period of more then eight weeks. Due
to the immobility of phosphorus in soil, it is important that phosphorus
fertilizer be placed close to the seed where the young plant has access to this
nutrient early in the season.
Adequate supply of
phosphorus enables the plant to develop a strong, healthy rooting system early
in the season. This allows the plant to obtain nutrients and moisture from
lower depths in the soils and survive periods of drought that may occur later
in the growing season. Phosphorus helps rapeseed plants use moisture more
efficiently. Adequate phosphorus also results in more uniform blooming, good
seed production and faster maturity. Lack of available phosphorus results in a
poorly developed root system, reduced branching of plants, and reduced yield. A
severe phosphorus deficiency generally results in reduced growth and may show
up as a dark green or purplish coloration of the leaves.
Rapeseed takes up nearly
as much potassium and therefore, has a high potassium requirement (25kg/acre).
Potassium increases plant vigor, increases straw strength potassium helps speed
healing of wound from insects or hail and wind. When a soil is deficient in
potassium, the crop yield will be reduced, and responses to nitrogen and
phosphorus will be small. In severe cases of potassium deficiency, the edges of
older leaves will become yellow or scorched.
Rapeseed seedlings are
very susceptible to weed competition in the first few weeks after emergence. An
effective weed control during this period is vital. The crop canopy usually
closes 6 to 8 weeks after emergence and then rapeseed becomes an excellent weed
competitor due to increased canopy. Number of irrigation varies with
environmental conditions Temperature, rainfall, soil type, and variety/hybrid.
Generally rapeseed requires 3-4 irrigations depending upon rains. Moisture
stress during flowering, pod formation and seed development stages affects the
yield.
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