Canola agronomy and fit in northern farming systems

¹CSIRO Agriculture and Food 
²NSW DPI 

Take home message

• Identifying the optimal flowering window is an important consideration when growing canola in northern environments
• It is important to consider both biotic and abiotic stresses when identifying the optimal window
• Short to mid-season varieties are most suited to northern environments
• A large proportion of the final yield comes from the branches and should be considered when deciding to desiccate or windrow.

Background

This paper has been prepared as part of the GRDC funded project Optimised Canola Profitability (OCP) this is a collaborative project between NSW DPI, CSIRO, SARDI and GRDC. A strong focus of the research to date has been on investigating the interactions between sowing date and variety choice of canola as it relates to phenology, biomass accumulation, grain yield and oil concentration. This focus has arisen from the practice of planting canola earlier in southern Australia as a way of capturing a dual purpose use, improving the crops water use efficiency, increasing yield and adapting to early seasonal breaks. The earlier sowing of canola in the southern states has identified differences in canola genetics, where the time to flowering in some varieties differs from when they are planted within their traditional window. The process of identifying and understanding the different flowering process has helped identify canola cultivars and agronomic practices that can help improve the production of canola in the northern grains region.

Detailed flowering trials that included the extension of day length and monitoring of low temperature sensitivity were established in Queensland and Canberra; while variety by sowing date experiments were planted across the Northern and Southern GRDC regions in 2014,2015, and 2016. These trials extended from the Darling Downs in SE Queensland to Tamworth and the Breeza plain, Narrabri and then on to Canowindra on the central-west slopes of NSW, Horsham in the Wimmera region of Victoria and west to the Eyre Peninsula in South Australia. This paper will use some of these results to highlight issues to consider if including canola within a northern farming system.

Identifying the optimal flowering date

Like chickpeas, canola is an indeterminate plant (will continue to flower while they have water and mild temperatures), unlike chickpeas, however, canola can withstand colder temperatures during flowering, but the flowers and particularly the pods are sensitive to frost. In selecting an optimal flowering window, the aim is to avoid frost during the sensitive pod filling period.  

On the other end of the season, high temperatures even for short periods can cause stress resulting in yield loss. Higher temperatures can also reduce the quantity and quality of the oil produced. Temperatures above 25°C can inhibit the build-up of oleic acid and therefore alter the fatty acid composition of the oil.

The detailed phenology work that has been a key part of the (OCP) project has been captured within the APSIM canola model, this combined with field trials conducted across the region has allowed us to identify the best time for flowering to occur. The optimum time to flowering is a period calculated from the model that has been adjusted to consider high temperature and frost stress.

The figure below (Figure 1) describes the optimum flowering window for Moree the grey bar depicts the window when flowering should commence. The predicted yield (black line) decreases from this point because water stress (dotted) and heat (dashed) lines increase the stress on the crop. This data is a summary from 50 years of crops planted on a range of sowing dates using short and medium length canola cultivars.

Figure 1.  Simulated optimal flowering window for canola production in Moree for short to mid season cultivars. The solid line indicates the frost and heat modified yield. The dotted line indicates increasing water stress and the dashed lines indicate frost and heat stress (frost to August, heat from August).

Once the optimum flowering window has been identified it is important to work backwards and find cultivars that have the correct genetics to flower in this period. For Moree a range of phenology types are presented (Figure 2). The long season types or the winter types are not suited to Moree because they flower too late (not shown). The short season and medium short cultivars are more suitable. Archer is a midum long season and is a possibility for a very early planting, more testing is required.  

These results are supported by the trial results collected last year (table1), however, it must be remembered that 2016 was not a typical season with a mild winter and spring allowing good growth well into spring, which resulted in high yields (Table 2).

 Figure 2. Showing the sowing dates required to flower within the optimal flowering period for different cultivar types.

Table 1.  Flowering dates for some current commercial cultivars sown at different times across the northen grains region during 2016

Table 2. Yields achieved in time of sowing trials from three sites across the northern grains region.

*43C80 CL and 45Y86 CL had poor establishment from the 17 May sowing date at Trangie so were excluded from the analysis.

Is there a benefit of planting early

Work from the southern grains regions is showing that if rain occurs in ealy April (early sowing) good yields can be achieved by sowing a mid to long season cultivar that flowers in the optimal flowering window. However, this is not the case in warm or northern environments where the warmer conditions prevent longer season cultivars from flowering during the optimum flowering window.  Some good, short to medium length cultivars are available for northern environments.

Harvesting

A successful canola crop should be planted at a time and with a cultivar that enables flowering to occur within the optimum flowering window. A good profile of stored water and sufficient nitrogen will give the crop the best chance of success. The next important issue is how to harvest that crop. Work conducted by NSW DPI as part of the optimising canola project is identifying ways to maintain yield when harvesting canola. The current industry guidelines recommend that canola is ready to windrow when 40-60% of seeds on the primary stem change colour from green to red ,brown or black. However, data from trials conducted in 2015 and 2016 are showing that on average only 25-30 % of the grain is being held on the main stem. This work is showing that later harvesting/windrowing up to 95% colour change on the main stem  will increase yield and oil concentration. The tradeoff with delaying is losses through shattering or weather damage, so suggested recommendations are to consider upcoming weather forecasts and windrow when more than 40 % of the mainstem seed has changed colour. If planning to desiccate and direct head, desiccants should be applied after 20% mainstem seed colour change has occurred.   

Acknowledgements

This work is a component of the 'Optimised Canola Profitability' project (CSP00187), a collaboration between CSIRO, NSW DPI, and GRDC, in partnership with SARDI, CSU, MSF and BCG.

Contact details

Jeremy Whish
CSIRO Agriculture and Food
Email: Jeremy.Whish@csiro.au