Optimised canola profitability project

¹NSW DPI and ²CSIRO Canberra

Take home messages

• Early sowing (early April) of canola exposes the inherent phenological differences between commercial canola varieties – choose wisely!
• In 2016 (with the exception of the most northern site Breeza) slower developing varieties maintained relatively consistent yield across sowing dates.
• Early sowing limited yield of fast developing varieties at both Wagga Wagga and Condobolin due to early flowering which increased exposure to fungal diseases and reduced biomass and yield potential.
• There was a strong relationship between final biomass and grain yield
• Certain varieties convert biomass more efficiently into grain yield (higher HI)
• Aim to plant canola in paddocks with a high starting nitrogen availability or be prepared to feed it

Introduction

Optimised Canola Profitability (OCP) 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. Variety by sowing date experiments were planted across the Northern and Southern GRDC regions in 2016, from the Darling Downs in SE Queensland, 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 presents an overview of results from across NSW including nitrogen trials. Further results will be available as samples are processed over the coming weeks.

Phenology of commercial cultivars - 2016

An understanding of varietal phenology as well as characterisation of a particular environment enables variety choice and sowing date decisions to target optimum flowering time to reduce frost, heat and moisture stress risks during reproductive development. Radiation also influences the optimum flowering window due to the positive relationship between intercepted radiation and seed number. Record low radiation levels in 2016 together with high rainfall, warm winter temperatures and low spring temperatures made this an important issue.

To determine the varietal response to sowing date, a diverse set of varieties was sown in experiments at a range of locations in 2016 (Table 2). This paper reports on phenology and grain yield results from five sites – Wagga Wagga (eastern Riverina, NSW), Ganmain (north-eastern Riverina, NSW), Condobolin (CW Plains NSW), Trangie (CW Plains NSW) and Breeza (Liverpool Plains, NSW). Common across these sites in 2016 was well above average (or near record) rainfall, cool spring temperatures (no major heat events) and very low incoming solar radiation during winter and spring (lowest on record for the period from May to October).

Table 1. Location, fallow rainfall (November to March), in-crop rainfall (April to October), soil nitrogen at sowing and nitrogen applied to five canola experimental sites across NSW in 2016.

* To ensure timely establishment, early sowing of the trials were irrigated with small amounts of water.

Archer was the slowest variety to flower (determined as 50% of plants with one open flower) from early sowing at each site, with the most consistent flowering date across sowing dates (Table 2). At Wagga Wagga, there was 19 days difference in flowering date of Archer between sowing on 31 March and 29 April. In contrast, there was 59 days difference in flowering date for the same sowing dates of Nuseed Diamond. The ability of Archer to flower in a tight flowering window regardless of sowing date means that it has a wide and flexible sowing window. Other varieties with a similar (but lesser) ability to regulate their flowering window at earlier sowings (early April) include ATR Wahoo, Pioneer 45Y25 RR, Hyola 725RT and Hyola 600RR. Varieties that are generally very quick to flower from early sowing include Nuseed Diamond, ATR Stingray, IH30RR and Hyola 575CL. 

Table 2. Date of flowering (50% of plants with one open flower) of canola varieties sown at two or three sowing dates at five sites across NSW in 2016.

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

When should canola flower?

Preliminary research in 2016 (data to be presented in more detail at GRDC Update) suggests that the critical stage for yield potential of canola is between 100 and 500 degree days (°C.days) after the commencement of flowering. Stress that reduces growth during this period has the biggest impact on grain yield. For an average mid-late winter day at Wagga Wagga, this would mean that the critical period commences around 10 days after the start of flowering and continues for four weeks.

The critical growth period needs to coincide with the optimal environmental conditions (critical flowering windows) i.e. when the risk of frost, heat and moisture stress are minimised and yet there is sufficient radiation to provide energy for growth. The critical flowering window for canola across a range of environments is being characterised as part of the OCP project.  

Sowing date and grain yield – 2016

At Wagga Wagga, long season varieties such as Archer, GT50 RR and Hyola 600RR maintained consistent grain yield across sowing dates (Table 3), and GT50 RR was the only variety to yield above 4 t/ha from each sowing date. The highest individual treatment yield was Nuseed Diamond sown on 29 April, yielding 4.8 t/ha. Fast developing varieties such as Nuseed Diamond, ATR Stingray, Pioneer 44Y89 (CL) and Hyola 575CL yielded less from early sowing, partly because flowering occurred too early to maximise biomass and seed number.

In addition to the reduced biomass from early sowing, Nuseed Diamond and ATR Stingray had increased disease infection (despite multiple applications of fungicide). The very early flowering (June) of these varieties exposed them to infection events all through winter, with the grain yield of Nuseed Diamond reduced by Sclerotinia (approx. 25% of plants infected) and the grain yield of ATR Stingray reduced by upper canopy blackleg infection (greater than 50% of pods infected).

Table 3. Grain yield of 16 canola varieties sown at two or three sowing dates across NSW in 2016-

*43C80 CL and 45Y86 CL had poor establishment from the 17 May sowing date at Trangie so were excluded from the analysis.
¹Nitrogen treatments were included at Finley, Ganmain and Condobolin. Yield results are reported for the highest N rate in each experiment.
²At Breeza, the interaction between variety and sowing date was not significant so only the effect of sowing date and associated l.s.d. is reported.

At Ganmain there was no effect of sowing date on grain yield, but the hybrid Clearfield varieties Pioneer 44Y89 CL and Archer were both significantly higher yielding than the open-pollinated TT varieties, ATR Stingray and ATR Wahoo.

At Condobolin, the yield of the fast developing varieties ATR Stingray  and Pioneer 44Y89 (CL) was reduced by early sowing (disease level not significant), but the grain yield of Archer and ATR Wahoo  was consistent across sowing dates. Comparing varieties with similar phenology (and similar to the finding at Ganmain), Pioneer 44Y89 (CL) was higher yielding than ATR Stingray  and Archer was higher yielding than ATR Wahoo.

At Trangie, the four varieties that were sown at each of the three sowing dates all had their highest grain yield from either the first (1 April) or second sowing date (14 April).

There was no interaction between variety and sowing date at Breeza, meaning that all varieties followed a similar yield trend across sowing dates. The last sowing date (17 June) was the highest yielding sowing date at 4.4 t/ha compared with 3.3 t/ha for the first sowing date (13 April) and 4.0 t/ha for the second sowing date (16 May). There were also differences between varieties at Breeza, with Pioneer 44Y89 (CL) being the highest yielding variety.

Oil concentration

Analysis of oil concentration has only been completed on a few experiments. At Wagga Wagga there was an increase in oil concentration with delayed sowing (averaged across varieties). Oil concentration was 42.9% from 31 March sowing, 44.6% from 13 April sowing and 45.7% from 29 April sowing. At Trangie, the 17 May sowing date had the highest oil concentration (44.1%) compared with the 1 April and 14 April sowing dates (41.7% and 41.3% respectively)

This oil increase with delayed sowing is unusual as in most seasons it is expected that delayed sowing reduces oil concentration as the crop is exposed to more heat and moisture stress during reproductive stages.

Nitrogen response

At the Ganmain site as well as at a separate experimental site at Finley, nitrogen ‘indicator’ experiments were sown to determine the responsiveness of the individual trial sites. Rates of N up to 1000 kg/ha were included, with the N broadcast as urea in front of the seeder. Despite the physical separation of N, rates of 500 kg/ha and above generally reduced establishment so only rates up to 300 kg/ha are reported here.

At Finley (starting soil N 108 kg/ha) and Ganmain (starting soil N 129 t/ha), canola displayed its near ‘insatiable’ appetite for N, with positive grain yield responses up to N rates of 300 kg/ha (652 kg/ha urea) (Figure 1). Consistent with past research, increasing the rate of N reduced oil concentration at Finley (Ganmain data not yet available), with oil declining from 44.4% with nil N to 40.7% with 300 kg/ha N. Despite this lower oil concentration with the high N rate at Finley, the total amount of oil produced was greatly increased with the application of N, from 1.11 t/ha (nil N) to 1.45 t/ha (300 kg/ha N).

It could be quickly assumed that all canola growers should apply more N to their crops to increase grain yield potential, as similar results have been widely observed in previous seasons. The medium to long term strategy should be to target paddocks with relatively high soil N. Growers who planted pulses in 2016 should strongly consider planting canola in these paddocks in 2017 as they would likely have more water and N in the soil profile than cereal crops.

Figure 1. Effect of nitrogen (N) rate on grain yield of canola at Ganmain and Finley; and on oil concentration at Finley only in 2016.

Importance of timing of biomass accumulation

In the previous two years (2014-2015) of experiments, data showed that biomass at maturity had a positive linear relationship with grain yield. This was again demonstrated in 2016 (Figure 2); however when growth was divided into that which occurred pre-flowering (flowering biomass) and post-flowering, data shows that post-flowering growth had a greater influence on grain yield than pre-flowering growth (data presented for southern and central NSW sites only, Wagga Wagga, Finley, Ganmain and Condobolin).

Only at the waterlogged site at Ganmain was there a relationship between flowering biomass and grain yield. At Ganmain there was a linear relationship between biomass at flowering and grain yield but only for biomass levels below 5 t/ha.

Management tactics that optimise post-flowering growth will be further investigated in future years of research, but are likely to include timing of flowering, nitrogen management and variety choice.

Figure 2. Relationship between grain yield and biomass at flowering, growth post-flowering and biomass at maturity in canola trials at Wagga Wagga (×), Finley (▪), Ganmain (▲) and Condobolin (◊) in 2016.

Harvest index and biomass accumulation

Some varieties can achieve a higher grain yield per unit of total biomass grown, referred to as harvest index (HI). At Wagga Wagga in 2016, ATR Stingray had the highest harvest index but had the lowest biomass at maturity, so its grain yield was at the lower end of the varieties (averaged across sowing dates). Nuseed Diamond stands out as a variety that grows at least moderate levels of biomass but also has a high conversion of that biomass into grain. Nuseed Diamond grew a similar amount of total biomass as Pioneer 45Y88 CL, Pioneer 44Y89 CL, Hyola 725 RT and GT50 RR but had a 17%, 10%, 21% and 10% higher harvest index, respectively over these varieties. The ability of some varieties to grow good quantities of biomass and then convert this biomass more efficiently into grain yield will be a focus of future research.

Conclusion

The OCP project has demonstrated that there are some varieties that have a wide planting window, allowing sowing opportunities to be captured when they arise, that can often match the yields of later-sown varieties. Such varieties may not always be the highest yielding but do offer greater flexibility to the farming system. In contrast there are fast developing varieties that should only be planted late in the sowing window to avoid reduced grain yield potential and increased disease risk.

The 2016 season has reinforced the importance of adequate nitrogen for canola. The best variety choice and sowing date management without appropriate nitrogen management is a lost opportunity. Growers need to ensure that approximately 80 kg/ha of nitrogen is available to the crop per tonne of targeted grain yield. With declining levels of soil fertility generally, this means nitrogen requirements are being met more and more by fertiliser rather than soil reserves. Aiming to plant canola in high N situations will greatly reduce the risk associated with growing canola.

Acknowledgements

Thanks to all technical staff for their assistance with these experiments, including Rod Bambach, Steve Morphett, Jan Hosking, Scott Richards, Nick Hill, Sharni Hands, Warren Bartlett, Danielle Malcolm, Jess Simpson and Daryl Reardon.

Thanks also to trial co-operators, Ben Beck at Wagga Wagga and Dennis and Dianne Brill at Ganmain.

The research undertaken as part of this project is made possible by the significant contributions of growers through both trial cooperation and the support of the GRDC, the author would like to thank them for their continued support.

Email: rohan.brill@dpi.nsw.gov.au