best practice management guide for south-eastern Australia - Grains ...

Canola in the low-rainfall cropping zone
cent per week in NSW for each week’s delay in sowing
past the optimum time. Delayed sowing can also reduce oil
content by about 0.5–0.8 percentage oil points per week.
Variety maturity x sowing time interaction
Although the general rule is for early sowing for maximum
yield and oil content, varieties with an appropriate maturity
class need to be chosen for a given sowing time. Do not
sow early maturing varieties early. Mid April sowing of early
maturing varieties can result in frost damage during pod
filling and this can be costly in better seasons.
Early flowering and maturing cultivars avoid some of
the high temperature and moisture stress likely in spring.
Brassica juncea (Indian mustard) has been developed for
lower rainfall areas. The main advantages over canola are
better heat and moisture stress tolerance.
No-till canola crop establishing well near Nyngan NSW. Photo: G. Brooke, NSW DPI
Optimal row spacing will vary for different low rainfall environments.
Photo: P. Parker, NSW DPI
with stubble retention, maintains sowing moisture in the
surface layers of the soil, and can extend the period when
it is possible to sow canola after the previous rainfall event.
Sowing can also occur on smaller rainfall events, which are
common in the low-rainfall cropping zone. Low disturbance
seeding is preferable when sowing early as less soil drying
occurs. Rain following conventional sowing often leads to
crusting. This problem is reduced by stubble retention and
no-till seeding. Modern guidance systems and controlled
traffic allow inter-row seeding in no-till systems.
Early sowing within the sowing window
In the absence of severe frost, generally the earlier the crop
is sown the higher the potential yield. Sowing time for canola
is a compromise between sowing late enough to minimise
frost injury in the early spring and early enough to minimise
high temperatures and moisture stress. Early sown crops
can better utilise stored moisture from depth. However, if
crops are sown too early they may flower in mid winter and
therefore be frosted.
Optimal sowing time for the low rainfall zones of NSW,
Victoria and South Australia is discussed in detail in
Chapter 5. To summarise, expect a yield penalty of five per
cent per week in South Australia and Victoria, and 10 per
Plant population
In the low rainfall zone, aim for a lower plant stand than in
medium and high rainfall zones. A uniform plant stand is
critical for reaching yield potential in this zone. It improves
weed competition, promotes more even growth and maturity
and sets the crop up for the best possible yield.
Recommended plant populations are discussed in
Chapter 5 for each area within the low rainfall zone of southeast
Australia. Plant population targets are generally lower in
the low-rainfall zone of NSW (30–50 plants/m 2 ), where subsoil
moisture is more critical. In South Australia, 40–70 plants/m 2
is recommended, as the crop relies more on in-crop rainfall.
The Victorian Mallee has similar targets to NSW.
Row spacing
Row spacing configurations in the low rainfall zone have
been adopted to suit stubble retention and no-till seeding
as much as any consideration for the crop. Optimal row
spacing will vary depending on subsoil moisture, sowing
time and growing season temperatures.
In the summer dominant rainfall areas of north-west NSW,
growers use wide rows (60–66 cm) to manage stored soil
moisture because of greater uncertainty of in-crop rainfall. Row
spacings of 30–33 cm are widely used in the low-rainfall western
areas of central and southern NSW, in the Victorian Mallee and
in South Australia, although some narrower (18–25 cm) spacings
are still used. Wider rows tend to result in lower establishment
rates for a given seeding rate, presumably due to seedling
competition within the plant row. Wider rows also promote taller
plants if there are too many plants in the plant row.
Correct nutrition
Less than optimal nutrition can reduce yields and lower water
use efficiencies in marginal environments. Ensure nitrogen,
phosphorus and sulfur rates are adequate to achieve the
target yield. Zinc may also be required on alkaline grey soils.
To calculate fertiliser requirements refer to Chapter 7. Do not
apply more than 10 kg/ha nitrogen with the seed in low-rainfall
areas, especially when sowing early into warm soils, and take
care with nitrogen rates with the seed on wider row spacings.
30 Canola best practice management guide