Paddock Practices: Canola - linking variety choice to time of sowing, to drive profitability of early sown canola
Author: Toni Somes | Date: 18 Apr 2018
Growers considering planting canola this season could benefit from learnings from last year’s tough conditions, which reinforced the importance of flowering time and emphasised how following 10 key guidelines can improve the profitability of early sown canola.
- Consider your location
- Select a slower developing variety
- Manage fallows and residues
- Manage seed placement
- Adjust seeding rates
- Carefully manage weeds
- Select fertile paddocks
- Consider pests and insect
- Consider disease pressure
- Assess croptop/windrow timing
The Optimised Canola Profitability research project - a collaboration between the GRDC, CSIRO, New South Wales Department of Primary Industries (DPI) and the South Australian Research and Development Institute (SARDI) - involved 34 paddock trials run from 2014 to 2016, has been investigating the interaction between variety and sowing date.
The project focused on quantifying potential yield and grain quality benefits from sowing crops in early to mid-April and investigated the tactical agronomic requirements to achieve successful outcomes, by looking at varieties suitable for earlier sowing and their management.
Trial sites 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’s leaders, research agronomist Rohan Brill from the New South Wales Department of Primary Industries (DPI) said the experience in the paddock last season (2017) supported research findings, which showed even in a tough season sowing canola early and getting the agronomy right improved yields.
“In the western cropping region of southern NSW (west of Wagga Wagga), extreme weather conditions experienced in 2017 made it difficult to grow profitable canola, yet there were crops that were profitable with grain yield of 1 to 2t/ha even in the same landscape where many crops yielded less than 0.5t/ha,” Mr Brill said.
“In the eastern half of southern NSW, although much drier than average in 2017, canola yielded close to average with some exceptional results on the upper slopes.”
But differences between crop yields on a local scale weren’t so much due to differences in the environment or seasonal conditions, rather Mr Brill said came down to management factors like ensuring a weed free fallow, maintaining ground cover over summer and matching sowing date and variety.
Timing, varietal choice and nutrition vital
“The main message from 2017 is the importance of matching sowing date with varietal phenology to flower at the right time, reaffirming a consistent message from years of canola research,” he said.
“Secondly, to achieve high yield, growers need to manage the crop with optimum nitrogen fertility and finally with the former two manageable factors in place, research data shows hybrid varieties can take grain yield to the next level.
“But that said variety choice isn’t a silver bullet in isolation, growers need to get time of sowing right and manage crop nutrition effectively.”
Mr Brill said although frost had a major impact on grain yield in 2017, especially in western areas, there were management decisions that significantly affected how crops recovered.
“Matching sowing date and phenology so crops flowered in the optimum window ensured that crops were not too far advanced through pod set when the frosts hit, but were also not so late that yield was limited by rising spring temperatures,” he said.
“Hybrids tended to recover better from frost damage (which requires further investigation) but it was still possible to achieve profitable yields with OP varieties.”
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 is northern NSW, where trials show significant yield variability with early April sowing - late April or early May is preferred.
Traditionally the 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, effective summer fallow management and improved no-till planting systems are enabling growers to capitalise on soil moisture opportunities and reduce production risk by sowing canola earlier”, Mr Brill said.
2 Select a slower developing variety
Early planting amplifies phenology differences between (spring) canola varieties. Plant 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.
Research showed slower developing varieties sown across a range of sowing dates had good flowering date stability and consistent yields, allowing flexibility to widen the sowing window if required (except in very dry environments). In contrast, some faster varieties sown early developed rapidly and flowered in early winter.
“Matching the phenology of a variety with sowing date was paramount for grain yield in 2017, largely avoiding major frost damage. At all sites, yield was reduced when flowering started before August,” Mr Brill said.
A sowing plan that incorporates two different canola phenology types (ie. varieties with different flowering times) can help optimise production across the enterprise.
- Fast or mid-fast developing varieties can have high yield potential but are not suited to early sowing.
- Select mid-slow or slow developing varieties for sowing before mid-April.
- Very slow (winter) dual purpose varieties can be sown in February or March in high rainfall zones, and in medium rainfall zones when the moisture profile allows.
“Hybrid canola generally outperformed open-pollinated (OP) canola especially in 2017, but sound agronomic management must accompany hybrids to maximise return on investment,” Mr Brill said.
“In high yielding environments, highest yield (above 3t/ha) resulted from planting fast (e.g. Nuseed Diamond) and mid varieties (e.g. Pioneer® 45Y25 (RR) and Pioneer® 44Y90 (CL)) but the very slow winter varieties still had profitable yields when planted in late March or mid-April as grain only crops.
“There was an overall benefit of planting hybrid varieties; however varietal choice was less important than ensuring flowering date and N management were optimised.”
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.
Avoid placing high rates of fertiliser in direct contact with the seed - don’t exceed 10-12 kg/ha P. Disc seeding will minimise moisture loss and reduce clods when sowing early into marginal conditions but be aware of fertiliser toxicity.
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.
Vigorous, early-sown crops will help suppress weeds, but monitor crop growth stage for post-emergent herbicide applications as the timing will be earlier, possibly while still sowing later crops.
“As well as the in-crop agronomic management factors, pre-crop management had a major bearing on outcomes for canola in 2017,” Mr Brill said.
"Strict fallow and stubble management plus selecting the most suitable paddock for canola were critical for canola success in 2017 and need to be done well otherwise the best in-crop management will be futile.”
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.
“Canola responded well to high rates of nitrogen (N) at moderate yield levels (2.0t/ha), even in a dry and frosty year,” Mr Brill said.
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 and 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 crop-topping or windrow timing, check seed colour change across the whole plant, not just the main stem.
Rohan Brill, Wagga Wagga Agricultural Institute,
02 6938 1989
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