Sowing canola early in most southern and eastern Australian cropping regions can increase productivity and profitability by following 10 key tactical guidelines.
The guidelines – relating to location, variety selection, soil moisture management, seed placement and rates, weed, pest and disease management, soil nutrition and croptop/windrow timing – have been established after an extensive three-year investigation as part of a Grains Research and Development Corporation (GRDC) collaborative research investment.
Through the Optimised Canola Profitability project – a collaboration between the GRDC, CSIRO, New South Wales Department of Primary Industries and the South Australian Research and Development Institute (a division of Primary Industries and Regions SA) – 34 field experiments were conducted from 2014 to 2016, looking at the interaction between variety and sowing date.
The experiments were located at 14 sites, from Eyre Peninsula in South Australia and the Wimmera in Victoria through to the central-west slopes of NSW and the Darling Downs in south-eastern Queensland.
One of the project leaders, CSIRO research scientist Dr John Kirkegaard, says the traditional canola sowing window in much of the southern and eastern growing regions has opened in late April, continuing well into late May.
“However, changing rainfall patterns, disciplined summer fallow management and improved no-till seeding systems are enabling growers to capitalise on soil moisture opportunities and reduce production risk by sowing canola earlier in the season,” Dr Kirkegaard said.
“The project was established to quantify potential yield and grain quality benefits from sowing crops in early to mid-April and has focused on tactical agronomic requirements to achieve successful outcomes. We have been looking at varieties that are suitable for earlier sowing and how they should be managed.”
The guidelines for early-sown canola, developed with Rohan Brill (NSW DPI) and Andrew Ware (SARDI), have been published in a new electronic Ten Tips to Early-Sown Canola brochure. The 10 guidelines are:
1/ Consider your location – early sowing of canola before mid-April can be successful in most environments of southern and eastern Australia. The main exceptions are SA, where low rainfall probabilities in March-April are likely to restrict early sowing to around mid-April; and northern NSW, where trials show significant yield variability with early April sowing – late April or early May is preferred.
2/ Select a slower developing variety – early sowing amplifies phenology differences between (spring) canola varieties. Sow slower-developing varieties early to target the Optimal Start of Flowering period, i.e. the period when combined frost/heat/water stress is minimised and yield potential maximised. Sowing faster-developing varieties early will expose them to greater frost and disease risk at flowering and can reduce yield potential.
3/ Manage fallows and residues – management of soil moisture in the fallow period is critical for successful canola establishment. Control fallow weeds when they are small and before they start to use soil moisture. Consider potential residues, particularly from Group B herbicides and Group I herbicides in the previous crop and fallow. Spread residue evenly at harvest and retain until sowing to reduce moisture loss. Consider sowing canola after pulses, brown manure or long fallow to increase residual moisture in lower rainfall areas.
4/ Manage seed placement – consider placing seed slightly deeper (25-40 millimetres) for early sowing to account for higher evaporation rates. Reduce to 15-20 mm when dry sowing. If sowing retained open-pollinated (OP) seed, grade to at least 2 mm diameter to maximise establishment. Ensure the furrow is closed above the seed but avoid heavy press wheel pressure.
5/ Adjust seeding rates – establishment rates are usually lower when early sowing, with typically warmer temperatures and marginal moisture. As a guide, assume 40-50% establishment for early sowing compared with 60-70% for later sowing; use the higher end of the range for hybrid and large seeded OP seed. Increase seeding rates accordingly.
6/ Carefully manage weeds – early sowing usually occurs before annual weeds can germinate on the main autumn break. Select paddocks with a low weed burden and use a robust pre-emergent herbicide strategy. Select the herbicide tolerance package best suited to the weed spectrum and herbicide resistance status of the paddock.
7/ Select fertile paddocks – select paddocks high in nitrogen (N) to fully capture the higher yield potential of early sown crops. Aim for 80 kg/ha N per tonne of targeted grain yield. The rate of N is more important than the timing, although early sowing allows more opportunities for topdressing applications. In higher risk, low rainfall areas, sowing canola early with adequate N at seeding or early topdressing is a successful strategy.
8/ Consider pests and insects – aphid pressure can increase with early sowing but risks are reduced by controlling host weeds in the fallow period. Early sowing decreases the risk of red legged earth mite. Other pests, including slugs, earwigs and slaters, are more influenced by rotation and residue management than sowing time, although stubble retention is a successful strategy for early sowing.
9/ Consider disease pressure – early sowing can reduce the risk of blackleg crown canker in canola as young plants often develop several leaves before the onset of spore showers in autumn. Slow developing varieties sown early will flower at similar times to fast varieties sown later. Pressure from upper canopy blackleg and sclerotinia stem rot will therefore be similar and the same management practices apply. Note: If faster maturing varieties are sown too early in disease-prone areas there is increased risk of upper canopy infection, with significant impacts on yield.
10/ Assess croptop/windrow timing – early sown crops will generally branch more, particularly at lower plant densities, so a higher proportion of grain yield will be derived from branches than the main stem. Seed on branches matures slower than on the main stem. When assessing croptop or windrow timing, check seed colour change across the whole plant, not just the main stem.
The Ten Tips to Early-Sown Canola brochure also details Optimal Start of Flowering dates for Victoria, South Australia, central and southern NSW, and northern NSW and southern Queensland, and includes a table of proposed “phenology” ratings of canola varieties compared with commercial “maturity” ratings.