Disappointing on-farm oilseed rape yields are being mirrored by national variety trials results, with candidate varieties being especially below par.

Seed yields and overall gross output figures in the HGCA Recommended List trials were down by over 10% on the five-year rolling mean in the results, which was made up exclusively of English results on Monday [7 August].

“I expect some of the Scottish trials to have been harvested at the weekend,” HGCA RL manager Jim McVittie said.

There was little consistency from site to site this season, he said.

“The best guide for what is going to happen next year is to use the over-year rolling average.”

That left growers with a choice of several recommended varieties, including Lioness, NK Bravour, Excalibur, NK Grace, Castille and Toccata, all performing similarly for gross output.

And it meant other factors should be considered when choosing a variety next season.

“Look at the regional means, disease resistance, and whether you think a lower biomass-type variety or a more bulky variety suits your conditions,” he advised.

Candidate varieties in the RL trials had generally underperformed, but some varieties – such as Hornet, Clarence and Tuscan – had previously yielded better in northern trials, which had yet to be harvested this season, Dr McVittie pointed out.

However, two other candidates that were disappointing in RL trials – Excel and Excess – were leading TAG trials along with Expert and Castille, the organisation’s Christine Lilly said.

“Excel is doing 1-2% better than Castille.”

Overall, there was not very much consistency between sites, she said.

“There doesn’t appear to be much logic to explain the results.

Yields vary between 3.3 and 5.4t/ha, with most around 4.4-4.7t/ha.”

The difference in performance between the two sets of Excel and Excess results was being investigated by the breeder Matthew Clarke from Monsanto.

“The two organisation’s harvesting protocols are slightly different, so it might be due to that,” he suggested.

But the firm’s Castille was having an excellent year in both RL and TAG trials, he noted.

“It is down to stem canker resistance, good straw strength and its early maturity.”

mike.abram@rbi.co.uk