Canola can have an important role in northern NSW cropping systems, particularly in the higher rainfall areas of the region.
It generally yields 40 to 60% of wheat grown under similar conditions and in normal years, average yields of around 1.5 t/ha should be possible with good management. In the very dry year of 2002, canola yielded about 40% of wheat.
Canola has yielded over 3 t/ha in northern NSW under favourable soil and climatic conditions and can be expected to reduce root and crown rot diseases in the following wheat or barley crop.
Seasons which experience above average rainfall in winter and early spring tend to favour canola growth and under these conditions the crop can yield up to 60% of wheat. Oil contents of canola under such conditions are also higher. Canola does not tolerate drier seasons as well as wheat or barley.
Always sow on at least 80 cm depth of wet soil (approximately 150 mm of soil water) in eastern areas and 100 cm of wet soil (approximately 180 mm of soil water) in the drier western areas.
Computer modelling using the program APSIM has shown the importance of sowing canola into a good profile of stored water. At Walgett the model predicts canola production will be marginal if less than 55 cm of wet soil (100 mm of soil water) is available at sowing and in 50% of seasons, yields will be equal to or less than 1.2 t/ha. Whilst the model predicts that sowing at Gunnedah with 55 cm of wet soil (100 mm of soil water) would result in much higher yields in 50% of seasons of around 2 t/ha.
While many growers had poor experiences with growing canola in the early 1990’s, due to frost damage, improved varieties better adapted to northern conditions are now available. This coupled with improved agronomic information has renewed grower confidence in canola. However, in 2004 frosts in mid September and early October caused significant yield losses and reduced oil contents.
Key Management Issues
• Use no-tillage as it stores more soil moisture than conventional fallows.
• Ensure heavy stubble does not cover the plant line as it will impede canola establishment.
• Always sow on at least 80 cm depth of wet soil in eastern areas and 100 cm of wet soil in the drier western areas.
• Phosphate nutrition for canola is very important. Canola can respond to phosphorus on soils where wheat does not.
• Use similar rates of nitrogen on canola as you would for high protein wheat in the same soil.
• Grow varieties suitable for your conditions. Early maturing varieties are generally more suited to western areas, and mid season types to more favoured eastern growing areas. Grow several varieties to spread harvest timing and the risk of unfavourable events e.g. moisture stress and frost. Consider herbicide tolerant varieties e.g. triazine tolerant (TT) or Clearfield* where weeds are a problem.
• Sow mid season varieties from early May and early varieties from mid May to minimise frost risk.
• Aim to establish 30–50 plants per square metre, which can be achieved by sowing 2–4 kg of seed/ha.
• Monitor crops for insect pests during the critical times of establishment, flowering and podding. Take account of beneficial insect numbers when making decisions on control options.
• In rotation, canola is best followed with a winter cereal, as disease levels (e.g. crown rot) should be reduced and VAM* (Vesicular Arbuscular Mycorrhiza) is not a high requirement with these crops.
• Aphids – The last two seasons have seen high levels of aphids in spring, monitor aphid levels in autumn and spring to reduce the impact of virus transmission and crop stress from feeding.
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