OSR better able to tolerate wet feet in milder conditions

Despite a persistently wet autumn and winter season, which has seen rainfall records broken by some margin in many regions, average plant losses over winter in the trials are significantly lower, at 8% compared to 21% in 2022/23.

“In overall establishment terms, this season has proved much better for crops that survived the autumn, with 69% of seeds planted leading to plants in the spring, compared to 59% in 2022/23,” says Bayer technical manager Ellie Borthwick-North.

“It seems that wet weather in itself over winter isn’t necessarily a bad thing, it’s when oilseed rape sits both cold and wet that it struggles.”

The trials see seven mainstream Ex hybrids - DK Exstar, DK Excited, DK Extremus, DK Expose, DK Excentric together with coded varieties DMH470 and CWH515, clubroot hybrid DK Pledge and a HOLL variety - either V367OL or MDS77 - grown alongside a ‘control’ of Aurelia under commercial farm regimes at sites nationwide.

A combination of pest pressure and wet weather has resulted in more sites being lost this season than last, almost entirely as a result of cabbage stem flea beetle, with infestations hitting as crops struggled to establish in very wet conditions. Initial crop establishment was also less good than in autumn 2022.

Initial establishment

“Initial plant establishment, at 71%, was slightly less good than the 74% we saw in 2022, but crop development before winter (DBW) was a little faster, reflecting the much milder conditions,” says Ellie.

The milder winter has also resulted in noticeably faster rates of Development After Winter (DAW), which this season averaged 5.6 on a 1-9 scale, against 2.6 in 2023.

This very rapid rate of spring development, coupled with the ongoing wet weather, has made spring agronomy decisions around crop nutrition and crop protection challenging for many growers.

Desiccation timing

And while the mild conditions have enabled crops to grow away well and come into flowering in good condition in many cases, the prospect of an extended flowering period means that particular care will be needed with desiccation timing this season.

“If we do end up having an extended flowering period, it is going to be so important that crops are not desiccated too early,” says Ellie.

“There is still a lot of growing to be done and many crops clearly have reasonable potential, provided CSFB larval levels aren’t too bad and they are well enough rooted to deal with any summer dryness.

“We must aim to leave as much time as we possibly can before applying a desiccant in order to maximise pod fill and oil content.”

Forming one pillar of the rigorous Dekalb National Hybrid Proving Programme (NHPP,) which also includes small plot trials and specific character testing, the farm strip trials are providing an unrivalled insight into individual variety performance across regions, seasons and, importantly, at field-scale within commercial rotations.

“We can see, for example, that in terms of development, DK Excited, DK Exstar and DK Extremus continue to show the most rapid autumn growth, with DK Extremus and DK Exstar also proving the most rapid developers in spring.

“Meanwhile, DK Excentric is proving very similar to Aurelia in its establishment and autumn development and is slightly faster in its spring development,” says Ellie.

DK Excentric (right) looking a great complement to Aurelia (left. Flowering almost at the same time and with an equally a strong canopy structure)

Overall performance compared to a similar mix of varieties and sites in 2022/23