Key points

• Canola can be grown successfully with either March or early April sowing
• Sowing in March does not produce higher yields than sowing in April but provides further sowing opportunities for growers to consider, as seeding opportunities become more limited
• When sowing early, growers do not need to use a long-season variety in WA – a high-yielding adaptable early-mid variety proved a good fit in trials
• Risks are higher for very early sowing and need to be evaluated for each situation

Climate change is causing increasingly erratic seasonal breaks across the Western Australian wheatbelt, but also increasing frequency of March and early April rains. Enabling canola growers to extend the sowing window and successfully plant into early rain could help to compensate for the lack of autumn rainfall.

A GRDC-supported Western Australian Department of Primary Industries and Regional Development (DPIRD) project is exploring sowing canola very early to expand sowing opportunities.

The team includes DPIRD research scientists Stacey Power, Andrew Blake, Dr Imma Farre and Martin Harries.

Two years of research trials over low and medium-rainfall sites with sowing dates spanning March to June have shown that canola can be sown as early as 18 March without yield penalty.

However, the risks and rewards of considering such an early sowing need to be weighed up.

Eight large field trials with either four or five sowing times (19 March to 11 June, Table 1) were established at four low and medium-rainfall sites at Mullewa, Wongan Hills, Dale and Grass Patch over two seasons (2019-20). Plots were irrigated pre-seeding to mimic a good seeding opportunity and as necessary for crop survival post-seeding (post-seeding irrigation range for 18 March seeding in 2020, 70 millimetres at Mullewa and nil at Wongan Hills).

The varieties are shown in Figure 1 and include early maturity hybrid 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-late OP).

Very early sowing results

With very early sowing, on 18 March, all the varieties flowered at an earlier date, the flowering period was extended and phenology differences between varieties were magnified compared to later sowings. ATR Bonito flowered for more than a month longer when sown on 18 March at Dale, compared with end of April sowing (Figure 1).

Figure 1: Flowering of canola varieties from sowing dates of 18 March (top graph), 29 April (middle) and 11 June (bottom) at the Dale site in 2019. An example of the change in the length of the flowering window for ATR Bonito (PBR) is described for each time of sowing.

Source: Bucat, Power, Blake, Farre and Harries, DPIRD

Canola has advantages for very early sowing opportunities as its indeterminate flowering habit results in an extended flowering period, which can result in a higher number of pods, effectively setting a high yield potential.

Highest canola yields were from the 18 March or 8 April sowing times, as shown in Table 1.

Table 1: Average yield (t/ha) for triazine-tolerant canola types at five or four times of sowing over two years at three locations in Western Australia.

Source: DPIRD

For example, the highest-yielding trial was at Wongan Hills in 2020, where 18 March sowing yielded 3.4 tonnes per hectare and 8 April sowing yielded 3.2t/ha.

Sowing very early (March) did not have higher yields than early April but the big advantage is locking in the seeding opportunity.

Sowing in March or early April yielded more than half a tonne higher on average over all the trials, compared to late April seeding.

Contributing factors to high yields with early sowing are likely to include reduced heat stress during flowering and reduced drought stress during podding, when compared to traditional (29 April) sowing.

Variety maturity for early sowing

Using a longer-maturity variety is often recommended for early sowing to match flowering period with the longer growing season and, importantly, to reduce the risk of frost at the end of the flowering period, since the end of flowering is delayed (see Figure 1).

Where longer-maturity varieties (ATR Wahoo and SF Ignite) were sown, yields were generally highest at the first time of sowing.

However, 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 T4510 generally produced equal or higher yields compared with the longer-maturity varieties, at all times of sowing. However, local risks for frost should still be considered.

Having a high-yielding, early-mid variety will give growers adaptability for early or late sowing times.

Risks and rewards

The risks and rewards of considering such an early sowing need to be weighed up and are listed in Table 2. Growers should evaluate risks for each system and paddock using all available information, together with past experience. Follow-up rainfall after sowing is critical, especially in hotter northern regions. This risk was eliminated in the trials with access to post-seeding irrigation.

Soil and ambient temperatures can also affect crop establishment and this reduced establishment in the March seeding in all trials.

Frost during flowering, diseases, insects and predation are other risks to consider and these may be determined by the cropping history, location and topography of paddocks.

Table 2: Risks and rewards of very early sown canola derived from field experiments over two seasons.

Source: DPIRD

More information: Jackie Bucat, 08 9368 3481, jackie.bucat@dpird.wa.gov.au; GRDC Update paper 2021 When to take advantage of early seeding opportunities for canola in WA.