Canola - tactical agronomy still made a difference in a tough 2017

Call to action/take home messages

• In 2017, low yielding, unprofitable canola crops grew near profitable crops that had strict attention to the farming system and timely agronomic management.
• Matching the phenology of a variety with sowing date was paramount for grain yield, largely avoiding major frost damage. At all sites, yield was optimised with treatments that flowered close to the optimum start of flowering date (OSF).
• Canola responded well to high rates of nitrogen at moderate yield levels (2.0 t/ha), even in a dry and frosty year.
• Hybrid canola generally outperformed OP canola in 2017, but sound agronomic management must accompany hybrids to maximise return on the extra investment.

Introduction

In the western and northern cropping regions of NSW extreme weather conditions experienced in 2017 made it difficult to grow canola profitably, yet there were crops that were profitable with grain yield of 1.0 to 2.0 t/ha even in the same landscape where many crops yielded less than 0.5 t/ha. In the south-eastern half of NSW, although much drier than average in 2017, canola yielded close to average with some exceptional results on the upper slopes.

There were consistent messages coming from the crops that were profitable in 2017, including:

1. Strict fallow weed control that conserved soil moisture from the very wet spring in 2016.
2. Even straw spread at 2016 harvest and prudent stubble grazing management to reduce seedbed moisture loss in autumn, and cover maintained at least until sowing.
3. Selection of paddocks with relatively high starting soil water and nitrogen.
4. Matching phenology and sowing date so that flowering starts close to the optimum start of flowering (OSF) date to minimise environmental stresses and maximise growth.
5. Sowing hybrid canola varieties (although this alone did not guarantee success).
6. Application of sufficient nitrogen to match grain yield potential.
7. Some element of luck e.g. timely rainfall for establishment and high elevation that reduced frost damage.

This paper will cover research that particularly focussed on points 4 to 6 above, the agronomic management of the crop. The research reported here comes from two projects:

1. Optimised Canola Profitability (OCP) – a collaboration between NSW DPI, CSIRO, SARDI and GRDC, extending from southern Queensland to the Eyre Peninsula in SA.
2. High Yielding Canola (HYC) – a project funded under the new grains and pathology partnership between NSW DPI and GRDC. This project is based in southern NSW with sites in the south west slopes and in the Murrumbidgee irrigation area.

Optimum start of flowering (OSF) dates

For all grain crops there is a period in the growing season that is most favourable for flowering and reproductive development. This period will be where the risk of stress (such as frost, heat and drought) is minimised and where resource availability (water and light) is maximised. Recent enhancements in the APSIM model have enabled OSF (optimum start of flowering - defined as when 50% of plants have one open flower) dates to be identified for major canola growing locations, including for NSW in Table 1 (full document: 10 Tips for Early Sown Canola). This paper will report on the results from 2017 in the context of the simulated OSF dates for the three experimental sites.

Table 1. Optimum start of flowering (OSF) dates for key canola growing locations in NSW

2017 research

The site details of three experimental sites in NSW in 2017 reported in this paper are summarised in Table 2.

Table 2. Location, fallow rainfall (1 Nov to 31 March), in-crop rainfall (1 April to 31 October) and soil nitrogen at sowing at three canola experimental sites in 2017

* 25 mm of irrigation applied across whole site at Condobolin on 8-March to stimulate weeds and 15 mm applied on 13-April to ensure even establishment.

Condobolin

The experiment at Condobolin was designed to determine the optimum sowing date, plant type, phenology and nitrogen management to optimise biomass accumulation, harvest index and ultimately grain yield under two contrasting scenarios; irrigated (supplementary water rather than full irrigation) and dryland. Four varieties were sown in a full factorial combination of sowing date, nitrogen rate and added irrigation (150 mm, equivalent to 1.5 ML/ha) (Table 3). An irrigation treatment was included to determine if management of sowing date, variety type and nitrogen should vary under different moisture scenarios. The extreme frost events of 2017 did have a large impact on the outcome (major frosts on 1 July (-6.8°C), 2 July (-5.5°C), 12 July (-4.0°C), 22 July (-5.1°C), 29 July (-4.1°C), 20 August (-4.5°C), 29 August (-5.3°C) and 1 September (-3.9°C)), but success under these circumstances was still influenced by manageable factors.

Table 3. Treatments used in an agronomy experiment at Condobolin, 2017. Varieties (four), sowing dates (two), nitrogen rates (two), and irrigation treatments (two) were applied in a factorial combination.

¹All plots had 50 kg/ha N broadcast as urea before sowing. An extra 100 kg/ha of N was applied as urea for the 150 kg/ha treatment at 6-8 leaf stage.
²Two irrigations of 30 mm were applied to the irrigated treatment in March prior to sowing, one irrigation of 30 mm applied 20 June and four irrigations of 15 mm applied on 15 August, 1 September, 5 September and 20 September.

From the early (6 April) sowing, the fast varieties Nuseed® Diamond and ATR Stingray started flowering in late June/early July (Table 4), whereas the slower varieties Archer and ATR Wahoo flowered over a month later, starting in August. From the 20 April sowing, Nuseed Diamond and ATR Stingray flowered about two weeks earlier than Archer and ATR Wahoo sown on 6 April. Irrigation and the high N rate both delayed the start of flowering by 3 to 4 days.

Table 4. Start of flowering (50% of plants with one open flower) of four canola varieties sown at two sowing dates at Condobolin, 2017.

The mid-slow variety ATR Wahoo and the slow variety Archer both yielded around 1 t/ha in the dryland early sown treatment, as their delayed flowering meant they were not too far into podding when the severe frosts occurred (although some frost damage would have been sustained (Figure 1)). The yield of both Archer and ATR Wahoo was reduced by sowing later, as flowering was delayed until mid-August and pod development was limited by higher spring temperatures and greater water stress. The faster varieties Nuseed Diamond and ATR Stingray were heavily penalised by frost at both sowing dates as flowering started (from both sowing dates) before the OSF date of 25 July. It is recommended to sow these fast varieties after 25 April in most environments of southern NSW.

Figure 1. Grain yield of four canola varieties sown at two sowing dates, with (irrigated) or without (dryland) irrigation, at Condobolin in 2017 (l.s.d. P<0.05 = 0.26 t/ha).
(ATR Stingray and ATR Wahoo are protected under the Plant Breeders Rights Act 1994)

Irrigation (150 mm total) doubled the average experimental yield from 0.64 t/ha to 1.28 t/ha (Figure 1.). The increase in grain yield of the fast varieties from irrigation highlights the level of recovery that can be achieved by canola despite frost damage where sufficient soil water is available. While the main message of this experiment is that varietal phenology and sowing date need to be matched to avoid very early flowering of canola (before late July at this site), extra water can help frosted canola recover. The main ways that growers can reliably provide extra water to their crops is through strict fallow management and crop sequence decisions such as utilising pulses and long fallow in lower rainfall environments that may leave behind some deeper soil water that crop roots can access.

Despite the relatively low starting soil N level (77 kg/ha) at the Condobolin site, there was no response to increasing N rate from 50 to 150 kg/ha in either the irrigated or dryland treatment. The highest yielding treatment yielded 1.6 t/ha which would have required 144 kg/ha N to be available (assuming 50% efficiency), which would have been provided through a combination of mineral N, 50 kg/ha of applied N plus some mineralisation.

Ganmain

Similar to Condobolin, there were many severe frost events at Ganmain in 2017 (Figure 2), including 1 July (-5.5°C), 2-July (-4.1°C), 22 July (-3.5°C), 20 August (-3.4°C), 26 August (-3.1°C), 28 August (-4.4°C), 29 August (-5.7°C), 30 August (-3.5°C) and 17 September (-4.6°C). Rainfall was also well below average (long term average growing season rainfall = 275 mm) and there was a heat event of 36.3°C on 23 September (giving a temperature range of 40.9°C in less than one week!). Despite the extreme climatic conditions in 2017, average grain yield of the trial (2.1 t/ha) was still close to average for the region (1.8 to 2 t/ha) due to deep stored water from spring rainfall in 2016.

Figure 2. Temperature (°C) from 1 April to 31 October at the Ganmain experimental site, 2017

A frost scoring system was developed for Ganmain where the number of viable seeds was counted in 20 pods on the main stem in each plot. There was a strong relationship between flowering date and the number of viable seeds per pod (Figure 3). Early sown Nuseed Diamond and ATR Stingray flowered in early July and both averaged less than six seeds per pod. From the same sowing date, Archer and ATR Wahoo delayed their flowering until early-mid August and both had more than ten viable seeds per pod. This scoring gave an insight into the level of frost damage in each variety but did not completely relate to grain yield as there were differences in the ability to compensate (with new pods) from frost damage.

Figure 3. Viable seeds per pod (columns) and flowering date (× and Δ) of eight canola varieties sown at two sowing dates (averaged across N rates) at Ganmain, 2017 (Viable seeds/pod l.s.d. P<0.05 = 2.1). ATR Stingray, ATR Bonito and ATR Wahoo are protected under the Plant Breeders Rights Act 1994.

In this experiment, increased yield came from sowing varieties in their optimum window to achieve the OSF date (5 August for nearby Wagga Wagga) and where they were well fertilised with nitrogen (Figure 4). The fast varieties (Nuseed Diamond and ATR Stingray) were heavily penalised by frost from early sowing (early flowering, see flowering dates in Figure 3) and the slower varieties (e.g. Archer and ATR Wahoo) had reduced yield from later sowing as flowering occurred later (late August) than optimal and pod development was limited by rising spring temperatures. Importantly the nitrogen response increased for varieties sown in their correct window; for example there was a strong response to N with Archer, Pioneer 45Y25 RR and ATR Wahoo sown early (flowering in early August) but minimal response when sown later (flowering in later August). Conversely there was a strong response to N for Nuseed Diamond when sown later (flowering in early August) but not where it was sown early (flowering in early July). Both Pioneer® 44Y90 CL and Hyola® 600RR responded well to nitrogen at both sowing dates (Figure 4).

There was an overall benefit of planting hybrid varieties; however varietal choice was less important than ensuring sowing date, phenology and nitrogen management were optimised. For example, sowing the open-pollinated triazine tolerant variety ATR Wahoo (2.8 t/ha) early with a high rate of N yielded 0.7 t/ha above the trial mean yield of 2.1 t/ha, whereas there were several treatments where hybrids with inappropriate management yielded less than the trial mean.

Figure 4. Grain yield of eight canola varieties sown at two sowing dates and fertilised at two nitrogen rates at Ganmain, 2017 (l.s.d. P<0.05 = 0.38 t/ha).
(ATR Stingray, ATR Bonito and ATR Wahoo are protected under the Plant Breeders Rights Act 1994.)

Narrabri

An experiment was sown at Narrabri with six varieties (same as Ganmain but with the exception of the Roundup Ready® varieties Hyola 600RR and Pioneer 45Y25 (RR)), two sowing dates (19 April and 8 May) and two nitrogen rates, nil and 65 kg/ha N. The frosts were also severe at Narrabri with similar minimum temperatures recorded as Ganmain and Condobolin but with a greater diurnal (difference between minimum and maximum temperature) variation, i.e. the maximum temperatures were much higher (in excess of 20°C) on the same day as a -5°C frost event.

Figure 5. Start of flowering date of six canola varieties sown at two sowing dates at Narrabri, 2017.
(ATR Stingray, ATR Bonito and ATR Wahoo are protected under the Plant Breeders Rights Act 1994.)

The Narrabri trial had good early vigour and grew well but the frosts caused significant yield loss and there was little recovery as the season quickly transitioned from frosty to very warm and dry. Nuseed Diamond and ATR Stingray were the earliest varieties to flower (early July) from early sowing (Figure 5) but were the hardest hit by frost and yielded less than 0.1 t/ha. Later sown Nuseed Diamond that flowered on 1 August (close to the OSF date for Narrabri of 31 July) was the highest yielding treatment at 0.9 t/ha (Figure 6). There was no effect of increasing N rate to 65 kg/ha on grain yield.

Figure 6. Grain yield of six canola varieties sown at two sowing dates at Narrabri, 2017 (l.s.d. P<0.05 = 0.18 t/ha). ATR Stingray, ATR Bonito and ATR Wahoo are protected under the Plant Breeders Rights Act 1994.

Conclusion

Although in many regions 2017 was a tough year for growing canola, there were still profitable crops grown in most environments through effective management and in some cases a little luck (from timely rainfall) and paddock elevation. The correct matching of sowing date with phenology to target the OSF date for the location is the main message from 2017, reaffirming a consistent message from recent years of canola research. Secondly managing the crop with optimum nitrogen fertility, and finally with those factors in place, choosing hybrid varieties (especially in medium-high yielding environments).

Although frost had a major impact on grain yield in 2017, especially in western areas, there were management decisions that significantly affected how the crops recovered after frost. Matching sowing date and phenology so that crops flowered close to the OSF date ensured that crops were not too far advanced through pod set when the frosts hit but also not so late that yield was limited by rising spring temperatures. Hybrids tended to recover better from frost damage (which requires further investigation) but it was still possible to achieve profitable yields with OP varieties.

As well as the in-crop agronomic management factors the pre-crop management had a major bearing on outcomes for canola in 2017. Management of points 1 to 3 in the introduction including 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 to get the best return from the agronomic management.

Acknowledgements

The projects supporting this research are co-investments from GRDC, NSW DPI, CSIRO and SARDI. Thanks to technical staff for assistance including Craig Ryan, John Bromfield, Warren Bartlett, Sharni Hands and Sophie Prentice.

Further reading

10 Tips Early Sown Canola

Contact details

Rohan Brill
Wagga Wagga Agricultural Institute
Ph: 02 6938 1989
Email: rohan.brill@dpi.nsw.gov.au

Varieties displaying this symbol beside them are protected under the Plant Breeders Rights Act 1994

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