Canola growth and development - impact of time of sowing (TOS) and seasonal conditions

Andrew Ware¹, Rohan Brill², John Kirkegaard³, Sarah Noack⁴, Amanda Pearce⁵ and Leigh Davis⁶

¹SARDI, Port Lincoln; ²NSW DPI, Wagga Wagga;  ³CSIRO, Canberra; ⁴Hart Field Day Group; ⁵SARDI, Struan; ⁶SARDI, Minnipa

GRDC project code: CSP00187

Keywords: canola, varieties, time of sowing, phenology

Take home messages

• Understanding the drivers behind canola development will help to improve canola management and variety selection. 
• Varietal maturity ratings don’t always correlate with varietal phenology.
• Early sowing opportunities may provide a great opportunity to maximise canola yield, but selection of the correct variety is important.

Background

In 2014 preliminary field work commenced as part of a new five year GRDC project. This project will undertake physiological and agronomic research across nine regions in the Northern and Southern GRDC Zones from southern QLD to the Eyre Peninsula.  The project is designed to increase canola profitability and reduce production risk with tactical agronomy advice underpinned by physiological insights.

Despite the success of canola in Australian cropping systems, significant gaps remain in the underlying knowledge of canola physiology and agronomy, a situation exacerbated by its expansion into new areas and the release of new technologies including vigorous hybrid varieties with herbicide tolerance. Although growers recognise the high profit potential and the farming system benefits of canola, there remains a perceived risk of growing canola largely due to the high level of input required (e.g. seed, nitrogen fertiliser, sulphur fertiliser, windrowing). There is a need to determine the level of investment appropriate for these inputs on a regional scale and the agronomic management practices (for example sowing date decisions) that reduce the overall risk and increase the profitability of canola.

Sound tactical agronomic decisions require an improved physiological understanding of yield and oil formation in canola, and how they are affected by variety, environment and management (G x E x M).

Maximising canola yield and profit will improve through an increased understanding of canola physiology. This will occur through taking the following steps; (i) identifying the optimum flowering window to minimise heat and frost risk at specific sites, (ii) identifying the variety x sowing date combinations that achieve the optimum flowering window, (iii) managing the trajectory of biomass accumulation (of specific varieties) to maximise water-use efficiency, optimise N-use efficiency and minimise the risk of high input costs (e.g. seed costs, N, herbicide types, harvest strategies). Having optimised these steps further investigation may reveal specific varietal adaptations that provide yield advantage under specific stress (heat, drought, frost) or provide further G x E x M synergies.

As a first step, to improve the understanding between G x E x M interactions in current varieties, CSIRO conducted some pre-field experiment modelling using the best available information on variety development prior to 2014 trial work, and the APSIM model. This explored the potential for planting canola early at a number of locations across Australia and the potential yields that could be achieved by planting cultivars with differing maturity, at a number of sowing times. Table 1 summarises this work and shows there is potential for longer season varieties to be planted in locations such as Cummins and have an improved yield potential, however the opportunity for successfully sowing these varieties only occurs in 15% of years (where sufficient summer rainfall occurs).

This process highlighted a number of gaps in the understanding of many of the canola varieties currently being grown, and led to the 2014 trial program.

Methodology

As part of the GRDC Optimising Canola Profitability project three preliminary trials were established in South Australia in 2014; at Yeelanna (LEP), Hart (MN) and Lameroo (Mallee). Each trial featured the same six varieties (selected for a range of maturity times); three of the varieties were planted at two establishment rates (15pl/m² and 45pl/m²). Each of the variety treatments were sown at four sowing times, ranging from the earliest seed was available (mid-April) through to mid-June. A range of development stages were recorded throughout the season as well as grain yield.

A further two trials, part of a canola establishment project, funded by SAGIT, will also be reported here. These trials were located at Minnipa (UEP) and Wanilla (LEP). They also had four sowing times, but a limited number of cultivars.

Description of varieties used in 2014 time of sowing trials

ATR Gem

Early-mid maturity triazine tolerant variety. High oil content. Medium plant height. Blackleg resistance rating of MR (resistance group A). Tested in NVT trials 2011-14. Bred and marketed by Nuseed Pty Ltd.

ATR-Stingray

Early maturing triazine tolerant variety. Short height. Moderate-high oil content. Blackleg resistance rating MR (resistance group C).  Tested in NVT trials 2010-14. Bred by Nuseed Pty Ltd and DPI Victoria. Marketed by Nuseed Pty Ltd.

Pioneer® 44Y87 (CL)

Early-Mid maturing Clearfield hybrid. Moderate-high oil content. Medium plant height. Suited to medium rainfall areas. Blackleg resistance rating MR (resistance group A). Tested in NVT trials 2012-14.

Pioneer® 45Y88 (CL)

Mid maturing Clearfield hybrid. Moderate-high oil content. Medium plant height. Suited to medium-high rainfall. Blackleg resistance rating R-MR (resistance group A). Bred and marketed by DuPont Pioneer. Tested in NVT trials 2012-14.

Hyola® 559TT

Mid-Early maturing TT Hybrid. High oil content. Medium plant height. Ideally fits medium-low right through to high rainfall areas. Blackleg resistance rating R, (blackleg rotation groups A, B, D). Tested in NVT trials in 2012-14. Bred and marketed by Pacific Seeds.

Hyola® 575CL

Mid maturing Clearfield hybrid. High oil content. Medium plant height. Blackleg resistance rating R (resistance groups B, F). Tested in SA NVT trials in 2010-14. Bred and marketed by Pacific Seeds.

Hyola® 971CL

Late maturing winter Grain n Graze Clearfield hybrid. Extremely high biomass, good grain yield and oil content. Autumn and Spring sowing grain and graze option for very high rainfall or irrigated zones. Provisional blackleg rating of R-MR (resistance group A). Not tested in NVT trials. Marketed by Pacific Seeds.

Results and discussion

Results of 50% flowering dates are presented in Table 2. They show that when planted early, Hyola®575CL reaches flowering a considerable time (up to two weeks) before the other varieties trialled in 2014. Hyola®971CL, when planted in mid-April, had failed to reach flowering at all sites where it was trialled prior to 1 October. The other varieties trialled generally flowered within a few days of each other, with any differences becoming smaller by the last time of sowing.   

Table 2. 50% flowering dates recorded for each variety and each time of sowing at four sites, 2014. 

* Sown and irrigated with 8mm - through dripper hose

Table 3. Grain yield of canola comparing two different establishment rates (15 and 45 plants/m²) at three sites over four sowing times in 2014. 

* Sown and irrigated with 8mm - through dripper hose

Table 3 shows the different responses in grain yield to two different establishment rates (15 and 45 plants/ m²) recorded at Yeelanna, Hart and Lameroo. At Yeelanna, having the higher establishment rate (45pl/m²) produced significantly higher yields at each time of sowing. This reflects other work conducted by the SAGIT canola establishment project on this soil type. At the Hart site, establishment rate only became significant at the third and fourth times of sowing (16 May and 2 June), where having the higher seeding rate improved yields. This shows that while canola has a tremendous ability to compensate for poor establishment, in some situations having a poorly established crop will cost yield and needs to be factored into management.  

Table 4 shows that the variety Pioneer®45Y88CL yielded the highest at Yeelanna, Hart and Lameroo when planted in mid-April. The early May time of sowing, showed yield of all varieties, with the exception of ATR Gem and Hyola®971CL,  as being very similar. Results from the Hart trial didn't show any yield reduction when seeding was delayed to mid-May (third time of sowing) compared to early-May, however significant yield reductions occurred at the Wanilla site when comparing similar sowing times. This may reflect differences in soil water holding capacity of these two soils. To put the results from these trials in context the yield data from all South Australian NVT trials is shown in Table 5.  

Table 4. Grain yield from canola sown at four sowing times and five South Australian sites in 2014.

* Sown and irrigated with 8mm - through dripper hose

Table 5. SA canola variety NVT trial of yield performance (2014, expressed as % of site average yield)

Click on the table image to view a PDF (247kb) of Table 5.

Some of the differences in yields and plant development observed in the time of sowing trials can, in part, be explained by the drivers behind the development of each canola cultivar. There are three main controls of the development of canola; vernalisation response, photoperiod response and basic temperature response.  Each of these will play a differing role in every variety.

Vernalisation affects canola from sowing to floral initiation. Varietal response to vernalisation will manifest as reduced time taken from sowing to floral initiation as well as a reduced number of leaves at floral initiation. It is expected that early sowing of canola into a relatively warm period (viz. sowing in early April v mid May) will lead to a delay in the accumulation of vernalisation which will exacerbate the differences in flowering dates of varieties with different vernalisation requirements.

Varietal response to photoperiod occurs between emergence and floral initiation. Canola is a long day plant, meaning that the duration from sowing to floral initiation is reduced in long day situations. In recent studies, varieties commonly responded to day length in the range of 11 to 16 hours. For canola plants emerging in mid-April after an early April sowing, there is potential that some of the photoperiod requirement could be met in autumn where day length is longer than mid-winter.

The basic temperature response is essentially the response of a variety to thermal time (degree-days) when both photoperiod and vernalisation requirements are met. Although there are differences in the basic temperature response amongst commercial varieties in terms of time taken to floral initiation, it is generally less important than the differences as a result of vernalisation or photoperiod response. The basic temperature response is however the main driver of development after floral initiation.

Using the data collected from the South Australian and New South Wales trials collected in 2014 we can start to draw some conclusions about how some of the varieties trialled develop.

Hyola®971CL has a high vernalisation requirement. When this variety was sown in mid-April in the low to medium rainfall area of South Australia in 2014 flowering didn’t commence until the first week in October. Dry conditions through spring in all locations led to this variety being the lowest yielding in all trials.

Hyola®575CL appears to have a relatively flat thermal time requirement, regardless of when it is sown. This resulted in Hyola®575CL being the first variety to commence flowering when sown early. Results from the first time of sowing in all trials show that the yield of Hyola®575CL was lower compared to Pioneer®45Y88CL, meaning that it was a disadvantage to plant this variety early in 2014. The variety description of Hyola®575CL indicated it should have a mid-season maturity, similar to Pioneer®45Y88CL. 

Pioneer®44Y87CL showed that as sowing was delayed, thermal time requirement was reduced.  Further research is needed to understand why this occurred but it may have been due to a greater vernalisation requirement of Pioneer®44Y87CL  compared to Hyola®575CL, with early sowing taking longer to accumulate vernalisation than the later sowing dates.  This may have helped Pioneer®44Y87CL avoid some damage from early frost events.

Information generated by trials such as this into the future will add value to other trial results such as NVT and help explain difference in varietal adaptation, and performance as a starting point to growing more profitable canola.

Conclusion

The manner in which each canola variety develops can have a large influence on the resulting yield, when planted at different times, and in different environments. The challenge for this project, going forward, is to be able to develop and deliver information on new varieties in a way that is timely and relevant to growers and advisers. Growers and advisers will be able to use this information to help select a suite of varieties that are suited to sowing opportunities that most often occur in their district and also to capitalise on early or delayed sowing opportunities as the seasons dictate.

Contact details

Andrew Ware
PO Box 1783, PORT LINCOLN
0427 884 272
andrew.ware@sa.gov.au