When to take advantage of early seeding opportunities for canola in WA
Author: Jackie Bucat (Department of Primary Industries and Regional, South Perth), Stacey Power (DPIRD Northam), Martin Harries (DPIRD Geraldton and DPIRD South Perth), Andrew Blake (DPIRD Geraldton and DPIRD South Perth) and Imma Farre (DPIRD South Perth) | Date: 14 Apr 2021
Key messages
- Sowing in March did not produce higher yields than sowing in April but did provide further sowing opportunities for growers to consider
- Growers considering very early sowing should evaluate risk factors for their area and paddock, including an increased reliance on follow-up rain, low or staggered field emergence (due to higher temperatures at seeding), frost at end of flowering, insects (especially diamond back moth and green peach aphid) and animal predation, disease and weed control.
- Growers do not need to use a ‘long season’ variety when sowing in March or early April in the low or medium rainfall zone. In these experiments, the early-mid variety InVigor T 4510 generally produced equal or higher yields compared with the longer maturity varieties, at all times of sowing.
- To determine if a profitable canola crop can be grown from a March seeding.
- To compare the relative yield and profitability of different seeding times.
- To determine if it is best to use a long season variety for very early seeding opportunities.
Aims
- To determine if a profitable canola crop can be grown from a March seeding.
- To compare the relative yield and profitability of different seeding times.
- To determine if it is best to use a long season variety for very early seeding opportunities.
Introduction
Canola seeding has become progressively earlier during the past decade, with research confirming higher yields can be attained from a mid-April sowing compared with the traditional Anzac Day (25 April) sowing, (Harries and Seymour 2016). Many WA growers are considering even earlier sowing, primarily to take advantage of an existing seeding opportunity. This is likely to become an increasingly important driver, with climate change reducing the incidence of autumn rains. Seeding after early rain effectively increases the growing season rainfall and extends the growing season, which is important in short growing season areas, like Mullewa. There is a lack of experimental data on the consequences of sowing canola in WA before mid-April.
Method
Eight large field trials were established over the WA agricultural region, in low rainfall sites at Mullewa, and Grass Patch (data not reported) and medium rainfall sites at Wongan Hills and Dale (near Beverley), over two seasons (2019-2020). The trials had five times of sowing (TOS), starting on March 18 (very early sowing), then three weekly intervals at April 8 (early sowing), April 29 (‘traditional’ sowing), May 20 and June 11 (late sowing, 2019 only), standardised at all sites and both years.
The varieties were all Triazine Tolerant and included both open pollinated (OP) and hybrid plant types of a wide range of season lengths; Hyola 350TT, early-mid varieties ATR Bonito (OP), and InVigor T4510 (hybrid), and longer maturity, varieties SF Ignite (mid-late hybrid) and ATR Wahoo (mid OP), both with similar phenology although company listed harvest maturity was slightly different.
Seeding rate was calculated for a target density of 40 plants/m², with seeding rates near 2-3kg/ha with the notable exception of the large seeded Hyola 350TT in 2019, which had a seeding rate of 6.1kg/ha. Hybrid seed costs were $25, $28 and $22/kg for Hyola 350TT, InVigor T4510 and SF Ignite, respectively. All OP seed was budgeted for replacement and seed treatment at $3/kg.
Field plots were 10 or 12m long with four replicates. Each experiment was a split-plot design with sowing time as main plot, and varieties were completely randomised within sowing time blocks. Early sown plots were fenced and netted for protection from predation. Trials were monitored for phenology on a weekly basis, as well as standard assessments for density, crop height, biomass, harvest index, yield and oil.
Plots were irrigated pre-seeding and as necessary for crop survival post-seeding, with different amounts of irrigation applied to TOS treatments. Pre-seeding irrigation in 2019 was generally 40mm or less but post-seeding irrigation was higher than planned, up to 158mm at Mullewa TOS 1 (March 18), given that the season break was not until June 6 for most of the state. In 2020, pre-seeding irrigation was set to mimic the soil water from the wettest 20% of years in each location, which was 40mm for Wongan Hills and Dale and 50mm for Mullewa. Post-seeding irrigation was greatly reduced in 2020 and generally only required for TOS 1, apart from Mullewa, which used 70mm for TOS 1 (March 18), in 12 small instalments and 43mm for TOS 2. Growing season rainfall was around 180mm at Mullewa, 240mm at Wongan Hills and 320mm at Dale, over both 2019 and 2020.
Results
Phenology and growth
At Mullewa in 2019, flowering started at an earlier date for the March 18 sowing compared to the April 29 sowing (10% flowering of Hyola 350TT on May 12, compared to July 4), flowering extended over a longer period (77 days for ATR Bonito, compared with 33 days), and differences between varieties were magnified, with a six-week range in variety date of 50% flowering, compared with a three-week range for end of April seeding. This was a similar pattern for all sites and seasons. In particular, there was a significant decline in flowering duration with each sowing time, in each trial. An extended flowering period has been shown to set a higher number of pods (Harries et al 2018) effectively creating a high yield potential.
Figure 1. With very early sowing (a), flowering started at an earlier date, extended over a longer period and magnified differences between varieties, compared with a ‘traditional’ (b) sowing at Mullewa in 2019.
The extended flowering time with early sowing is due to the early maturity varieties accumulating their thermal time requirement more quickly, in the warmer conditions, while the flowering time of longer season varieties is consistent with a vernalisation response with a longer period of time required until temperatures satisfied this. Preliminary examination of the thermal time and vernalisation conditions supports this.
The phenology has been mapped with seasonal conditions, for example Mullewa in 2019 (Figure 2), illustrating incidences of frost at the end of flowering for March-sown plots, but avoidance of heat stress at the end of flowering. With a May sowing, there was heat stress close to flowering and lack of rainfall for grain fill (after flowering).
Average biomass from very early sowing ranged from 7t/ha at Mullewa in 2019, to 13.6t/ha at Wongan Hills in 2020. Biomass was highest and statistically similar for the first two sowing times at all sites, apart from Mullewa in 2019. In the Dale 2020 trial, biomass was statistically similar for all seeding times. Biomass is highly correlated with final yield (Zhang and Flottman 2016), effectively supporting grain fill towards yield potential.
Figure 2. Phenology overlayed with seasonal conditions for March 18 sowing (red line) and May 21 sowing (purple)
Yield, quality and profit
Trial yields were highest and similar with sowing on March 18 or April 8 for all trials. At Dale, there was no difference between yields of the first three TOS in 2020 and the first four TOS in 2019, reflecting the longer growing season at this site. Average TOS1 yields ranged between 1.4t/ha at Mullewa in 2019 and 3.4t/ha at Wongan Hills in 2020 (Table 1). The oil content (%) often declined with later seeding times, hence gross returns followed the same pattern as yield.
Table 1 Average yield (t/ha) was highest and similar with sowing on March 18 or April 8 for all trials.
Risk factors
Follow-up rain is the first risk factor for early sowing. This was evident at the warm northerly site of Mullewa where post-seeding irrigation for crop survival was 70mm in 2020, applied in 12 small applications, indicating a high demand at this site, compared with only one or two applications needed at other sites.
Plant establishment was significantly reduced for the March sowing at all sites. Since the sites had pre-seeding irrigation, this is likely to be due to high soil temperatures. Establishment was low for both March (16%) and early April (24%) sowings at Mullewa in 2020, compared with 48-76% for later sowing times. For the first two TOS, soil surface temperature was 38-40°C on nearby dry soil, and at 26-28°C in the moist seed bed at 1cm deep.
With very early sowing, there is a higher risk of frost at the end of seeding, which has been mapped for the 2019 Mullewa trial in Figure 2.
Predation and disease are other risk factors of early sowing. Insect predation was an issue with diamond back moth (DBM) infestation at our 2020 Grass patch site. The wet conditions for very early sowing provide host plants and the warm early conditions support rapid life cycles. Green peach aphid can also build up early in the season in a similar way. We also found bird and animal predation to be a major issue, so early sown plots were fenced and netted. Disease is more likely in early sown crops due to higher biomass and the longer flowering period providing an extended opportunity for sclerotinia infection. There were significant sclerotinia infections in the first two times of sowing at Dale in 2020, despite it being a relatively dry year. Weed control can also be more difficult, since ryegrass germination is delayed until cooler conditions.
Variety differences
Yields for the longer season varieties were generally highest at the first time of sowing, for both ATR Wahoo and SF Ignite. Hence, long season varieties are best sown early. However, the early-mid variety InVigor T4510 significantly out-yielded both longer season varieties at TOS 1 at Mullewa 2020 and Wongan Hills 2019 and yielded similarly to the longer season varieties in 2020 trials at Wongan Hills and Dale, while SF Ignite was highest yielding only at the 2019 Dale trial. In these experiments, choosing a high yielding variety was equally as important as using a longer maturity variety for early sowing opportunities. There may be a different outcome in longer season areas, or with new long-maturity varieties.
Conclusion
Sowing in March did not produce higher yields than sowing in April but did provide further sowing opportunities for growers to consider. Once the crop is established, there appeared to be no physiological disadvantages from early sowing and an earlier start to flowering.
Risk factors of early sowing include an increased reliance on follow-up rain, low or staggered field emergence (due to higher temperatures at seeding), frost at end of flowering, insects (especially diamond back moth and green peach aphid, which are both likely to build up in situations suited to very early sowing) and animal predation, disease and weed control. Growers should evaluate risks in their system, including seasonal outlook, heat conditions at seeding, if in a frost area or frost prone paddock, green bridge or insect host availability, likely presence of nearby canola paddocks, to alleviate predation pressure, and the presence of known predator populations, past disease pressure and rotation for disease risk management. Where growers are considering March sowing, reduce risk by seeding only part of the canola program at this time, increase the sowing rate of OP canola and monitor for pests and disease.
When sowing in March and early April, growers do not need to use a ‘long season’ variety in WA. In these experiments, the early-mid variety InVigor T 4510 generally produced equal or higher yields compared with the longer maturity varieties, at all times of sowing.
Acknowledgments
Acknowledgement and appreciation to DPIRD and GRDC for financial support (DAW 1901-005RTX). Thanks to Helen Cooper, Salzar Rhaman and Stephanie Boyce for excellent technical support, as well as trial management provided by DPIRD Field services units and Living Farm staff (Dale site). Thanks to farmers who hosted trials Glen and Eliza Thomas, Critch family, Bill and Anne Cleland, and Michael Ietto.
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.
Contact details
Jackie Bucat
Department of Primary Industries and Regional Development
1 Nash St, East Perth, WA, 6004
Phone: 9368 3481
Email: Jackie.Bucat@agric.wa.gov.au
GRDC Project Code: DAW 1901-005RTX,
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