Substantially increased oilseed rape crop confirmed in annual grower poll, despite bone-dry summer. CPM reports…

By Rob Jones

Despite a much more challenging autumn and later sowing than many planned, winter oilseed rape establishment across the country is remarkably good, reveal initial results from the fourth year of the Dekalb national establishment poll. This and the marked increase in plantings confirmed by the late October survey, suggests the area of crop coming into next spring could be up 10% on 2022.

Reports from over 230 growers, responsible for 25,000ha of current season plantings spread across the main arable areas of Great Britain, indicate just over 6% of this year’s crop has failed and therefore likely to be claimed for through breeders’ establishment schemes.

At the same time, growers rated over three quarters of this season’s crop at 7 or more for establishment on the poll’s standard 0-10 scale, with just 8% rated as less than 5 (Chart 1).

Chart 1: OSR establishment 

“Barring any major winter or early spring issues, these findings point to an overall crop survival to flowering similar to the past two years at around 90% of plantings,” says Lizzie Carr-Archer of
Bayer.

“This is a vast improvement on the 67% survival to spring we recorded in the last particularly challenging establishment season of 2019/20. And it’s certainly not what large numbers of growers were expecting as recently as September after such a bone-dry summer.”

With almost two thirds of growers reporting very or fairly dry conditions at sowing and only just over a third considering them at least reasonable, this year’s poll shows moisture levels at sowing were actually worse than 2019 (Chart 2).

Chart 2: Moisture conditions at sowing (2022 vs 2019)

Together with sowing delays prompted by the very dry conditions, this left many crops particularly open to the normal late August/early September cabbage stem flea beetle challenge.

While noticeably higher than the past two years, overall CSFB pressure proved to be well below the level of 2019, with just over 20% of growers reporting substantial and intense challenges from the pest compared with more than 50% three seasons ago (Chart 3).

Chart 3: CSFB pressure at establishment (2019 – 2022)

This, together with the fact that over 80% of growers reported receiving enough rainfall between sowing and late-October, probably contributesto the better position of the current crop going into winter, explains Lizzie.

“Our study shows considerable differences between the regions in CSFB pressure and moisture conditions, both at and after sowing. Even those areas faring worst, in terms of pest pressure and dryness, have better average establishment scores than 2019.

“Unsurprisingly, the much drier August led to a clear reversal of the trend towards earlier drilling we’ve been recording over the past three seasons, with nearly 60% of crops being sown after August 20 compared with 45% in 2021.

“Unlike in recent years, this also meant that earlier sown crops didn’t necessarily establish better than those going in at a more traditional late-August timing, despite what continued to be higher CSFB pressure at the time. This reinforces the fundamental importance of the balance between pest pressure and moisture conditions in determining OSR establishment,” she highlights.

“Our latest data shows CSFB pressure continues to have a greater impact on establishment than soil moisture. It really underlines that the real clincher in moisture terms is the amount of rainfall received after sowing rather than conditions at drilling. The difference in average establishment score between the extremes of CSFB pressure was almost twice that between the extremes of moisture at sowing (Chart 4).”

Chart 4: Establishment – differences between extremes of conditions

With drilling conditions so dry, it’s unsurprising that this year’s poll shows few overall differences in establishment success between different establishment regimes or variety types.

A noticeable gap was evident between how well hybrids coped with less than adequate rainfall after sowing compared with and pure line varieties (Chart 5). Together with lower levels of re-drilling (8% hybrids vs 11% conventionals), this underlines the benefits of modern hybrids’ establishment and early development vigour.

Chart 5: Establishment by variety type and conditions

“The greater CSFB pressures this season inevitably led to increased insecticide use at establishment than in recent years,” reports Lizzie.

“It’s really encouraging to see the proportion of growers deliberately avoiding insecticide spraying increasing slightly from 33% last season to 37% this year. Especially considering two thirds of those doing so – and more than three quarters of mainstream hybrid growers – still recorded establishment scores of 7 or more.

“This season’s poll gives particular confidence to those not letting the very dry early autumn put them off sticking with or increasing their OSR cropping,” she says.

“There’s a lot of water to go under the bridge still. However, the later sowing (and its known impact on reducing CSFB larvae) alongside the reported establishment scores leaves us quietly confident in a substantial year-on-year increase in the crop going to harvest.

“Even in the particularly damaging CSFB season of 2019/20, growers only recorded an average crop loss of around 6% between early spring and harvest,” concludes Lizzie.

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