Paddock Practices: Tips and tools to get the best out of early-sown canola crops

Key points

• Sowing early is key to optimising canola yields in most WA grainbelt areas
• During April is ideal for low and medium rainfall zones
• Delaying sowing in these areas can reduce yields by up to 40kg/ha/day
• April or May is the best sowing window for high rainfall zones
• Variety, seed size, seeding rate and placement varies with environment
• Consider climatic, weed, pest and disease risks
• Monitor crops closely for nitrogen and nutrition needs as the season unfolds.

Introduction

Sowing canola in early to mid-April is becoming standard practice in WA’s northern grainbelt and early sowing of the oilseed is growing in popularity in other parts of the State.

Summer rain, adoption of a summer fallow and improved no-till seeding systems enable growers to push the canola sowing window forward. But success depends on getting crop agronomy management right, starting with time of sowing and variety choice.

The Grains Research and Development Corporation’s collaborative ‘Optimised Canola Profitability’ project team has assessed the interaction between these key factors using 2014-17 trial data.

It found early sowing of canola can increase productivity and returns if some key tactical guidelines are followed. These are summarised further below.

In WA, the GRDC and Department of Primary Industries and Regional Development (DPIRD) ‘Tactical Break Crop Agronomy’ research team has also been trialling early sowing dates for canola.

This data has fed into a new resource called ‘Canola agronomy research in WA’. Read more about it in the Canola Agronomy Research in Western Australia bulletin.

This GRDC project aims to help growers in all rainfall zones achieve consistently high canola yields, especially in low and medium rainfall areas and for those transitioning from open pollinated (OP) to hybrid varieties and back again.

Location and time of sowing

Sowing canola early, before mid-April, is proving to be successful in parts of WA following summer rain and an early break - especially in the northern agricultural region.

Tactical Break Crop Agronomy team trials in 2015 at Binnu, assessing 10 varieties sown on April 15 and April 29 found:

• Overall site average yield of 1.3 tonnes per hectare
• Average yield of 1.6t/ha for April 15 sowing
• Average yield of 0.9t/ha for April 29 sowing
• Average loss of 43 kilograms/ha/day by delaying sowing 15 days
• Recently-released hybrids had highest yields
• Average yield of 1.4t/ha for Roundup Ready® (RR) varieties
• Average yields of 1.3t/ha for triazine tolerant (TT) varieties.

In the central grainbelt, Tactical Break Crop Agronomy team trials of six varieties in 2016 at Wongan Hills, sown on March 31 and April 15 found:

• Overall site average yield of 2.8t/ha
• Average yield of 2.8t/ha for March 31 sowing
• Average yield of 2.7t/ha for April 15 sowing
• Average loss of 13kg/ha/day by delaying sowing by 15 days
• No yield advantage for sowing early maturing varieties on March 31
• Yield bonus of 0.3t/ha (11 per cent) for sowing mid-season maturity varieties earlier
• Yield bonus of 0.2t/ha (10 per cent) for sowing mid/long-season maturity varieties earlier.

DPIRD development officer Jackie Bucat has assessed time of sowing results from trials right across WA and some key findings from her research to date include:

• Sowing after the start of May can reduce yields in some areas
• Average yield loss from sowing in mid-May or later is 15kg/ha/day
• Peak yield loss is 25kg/ha/day with sowing in the first two weeks of June
• Average yield loss is 0.5t/ha when sowing is delayed from mid-May to mid-June.

DPIRD modelling of the optimum sowing window for canola in WA to maximise grain yield has found long, or slow, maturing varieties are better suited to early sowing. It used 12 locations, three soil types and three canola varieties in the computer simulation analysis tool ‘APSIM-Canola’ and key findings are summarised in Table 1.

Overall, WA research to date indicates that if growers have a mid-April sowing opportunity for canola, they should take it to optimise yield potential. This will also help to reduce the risk of experiencing a long delay to the next sowing opportunity. More information from DPIRD can be found here.

DPIRD research officer Martin Harries has also produced a GRDC Grains Research Update paper outlining agronomy tips for early sown canola that can be found here.

Variety choice

When sowing early, it is typically recommended to use slower-developing canola varieties to target optimal flowering windows and minimise risks of frost, heat and moisture stress later in the season.

The GRDC-DPIRD ‘Canola agronomy research in WA’ resource has yield results from TT, RR, Clearfield® and conventional varieties.

In brief, WA research to date indicates:

• Yield differences are small between TT, Clearfield® and conventional canola in low rainfall zones and low yielding environments
• Yields of RR canola can be 0.2-0.3t/ha higher than TT in medium and high rainfall zones
• Weed control issues are central to variety and herbicide system decision-making
• It may be profitable to change from OP TT varieties to TT hybrid varieties when expected yield is more than 1.5t/ha.

WA’s 2019 Canola Variety Guide can be found here.

Fallow and residue management

For successful early canola sowing, it is recommended to:

• Spread residue evenly at harvest and retain until sowing to reduce moisture loss
• Control fallow weeds when small to minimise moisture use
• Consider potential herbicide residues, particularly from Group B and I, in the previous crop/fallow
• Consider sowing canola after pulses, brown manure or a long fallow (double break) to increase residual moisture in lower-rainfall areas.

Seed placement at sowing

When dry seeding in hot conditions, shallower sowing at 10-15mm has been found to produce higher yields than sowing at 30mm or 70mm.

DPIRD trials in the northern grainbelt show that there can be average yield losses of 18 and 65 per cent respectively when sowing at 30mm or 70mm.

Typically in WA trials, large-sized seed emerges better than smaller-sized seed in harsh sowing conditions. It is advised, if sowing retained OP seed, to grade it to at least 2mm in diameter to maximise establishment.

Other tips for seeding canola include:

• Close the furrow above the seed
• Avoid heavy press wheel pressure (especially on hard-setting soils and if rain is expected)
• If using disc seeding, be aware of fertiliser toxicity
• Avoid placing high rates of fertiliser in direct contact with seed
• Avoid using more than 10-12kg/ha phosphorus at sowing.

Seeding rates

Across Australia, canola establishment rates can drop when sowing early in warm temperatures and into marginal soil moisture.

Seed size matters and a seeding rate calculator can be found on the DPIRD website here.

Tips for getting seeding rate right and ensuring canola can compete with weeds include:

• Calculate target crop density using seed size and germination percentage
• Aim for a density of at least 20 plants/m²
• The best target range is 25-45 plants/m²
• OP varieties can be more profitable and at less production risk when at higher densities
• Density will be higher in high rainfall zones.

More information can be found on the DPIRD website here.

Weed management

As with all crops sown early in WA, weed control is vital to success.

It is advised to select paddocks with a low weed burden and to use a robust summer weed and pre-emergent herbicide strategy.

Vigorous, early sown crops will help to suppress weeds, but it is best to monitor crop growth stage for post-emergent herbicide applications. Timing of treatments may need to be earlier, possibly while still sowing later crops.

The WeedSmart website has a range of tips and tools for weed management. For example the 'big 6' of the WeedSmart plan.

Sow into fertile paddocks and get nutrition right

DPIRD research in WA has found most canola growers apply a proportion of nitrogen (N) at seeding and then ‘top-up’ about six to eight weeks after sowing.

This ability to tactically apply N is beneficial for early sowing, as it reduces up-front financial risks and allows growers to match N inputs and costs to yield potential better.

WA trials have shown that application of N at seeding, during the early vegetative stage or around the time of stem elongation tends to produce similar crop yields.

Some trials have found delaying N until 12 weeks after sowing (about the time of flowering) can lower seed yield or oil levels and lead to lower gross margins.

DPIRD recommends growers continue to aim to apply top-up N at eight weeks. But if conditions are uncertain, applying top-up N at 12 weeks may be a viable strategy - considering yield and market forecasts.

Pest and insect considerations

Aphid pressure can be higher in early sown canola crops, especially for green peach aphids if there is colonisation pre-flowering, but risks can be reduced by controlling host weeds in the fallow period.

Early sowing tends to reduce the risk of damage from 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 can be a successful strategy for early sowing.

Slugs can be problematic in high rainfall, no-till systems, particularly where heavy cereal residue remains from the previous year. Early monitoring is critical, as damage often first appears next to dams and drainage lines.

For more information contact Svetlana Micic, DPIRD, at: 08 9892 8444 svetlana.micic@dpird.wa.gov.au

More information

GRDC Research Codes

CSP00187; DAW00227

Contact

Martin Harries, DPIRD, 08 9956 8553, martin.harries@dpird.wa.gov.au
Jackie Bucat, DPIRD, 08 9368 3481, jackie.bucat@dpird.wa.gov.au
Imma Farre, DPIRD, 08 9363 4164, imma.farre@dpird.wa.gov.au

Useful resources

• Canola Agronomy Research in Western Australia bulletin
• 2019 Canola variety sowing guide for Western Australia
• Canola essentials - growing a successful canola crop
• Tactical break crop agronomy project: canola and pulse agronomy trials and information
• Canola sowing time to maximise yield in Western Australia
• New 10 tips to early sown canola