While selecting varieties that produce high seed yield is important, it is a very inconsistent trait influenced by several season-dependent factors, such as weather or disease and pest pressure.
Conversely, oil content is consistent across most seasons, according to Agrii’s technical seed manager David Leaper, and something growers can use to their advantage to increase revenue.
“It’s an uncannily stable characteristic and if you are growing a variety with an inherently high oil content, whether you get a low seed yield or high seed yield, you will still get a high oil content and subsequent bonus,” he explains.
A decade ago, varieties on the Recommended List had oil contents of 42-43%, but now there are a handful of varieties that are above 46%, including Agrii’s best-selling conventional Nikita at 46.3%.
The variety initially didn’t make the Recommended List two years ago due to its phoma score of 4, but was re-assessed and added last year for its high light leaf spot rating of 7, highlighting the increasing importance of resistance to the disease across the UK.
Other key characteristics include stiff straw, a fast growth habit – making it suitable for drilling into early September – and high gross output at 108% of controls, which is underpinned by its high oil content.
With growers paid a bonus of 1.5% of their contract price for every 1% oil above 40% and futures for harvest 2018 currently about £375/t, growing a 4t/ha crop of Nikita could return an additional £33.75/t or about £135/ha.
“Many other varieties on the list are around 44%, so the bonus will be lower at around £22.50/t, or £90/ha. Although it’s a small difference, it’s all extra income to the farm,” explains Mr Leaper.
Agrovista’s national seed manager Nigel Walley agrees oil bonus is a key consideration when selecting a variety, particularly as the price picks up following a few bearish seasons.
The agronomy and distribution group will be marketing Annalise this summer, which has the highest oil content of any recommended or candidate variety at 46.9%, plus a gross output of 105% in the East/West region and 106% in the North.
Mr Walley says the conventional candidate could offer an attractive oil bonus for growers and it also has other valuable characteristics, namely its resistance to turnip yellows virus (TuYV).
The disease has been on the rise in recent years and after the loss of neonicotinoid seed treatments, and increasing resistance to insecticides, using varietal resistance is the arguably the most reliable way of protecting yield from autumn infection via its main vector, the peach potato aphid.
Amalie – currently the only TuYV-resistant variety on the list – has been an asset according to Mr Walley, but its gross output is now 12-14% down on leading varieties, but Annalise is just 5% off the top spot, so a likely recommendation this year will be a game changer.
“You can see up to a 30% yield decrease from TuYV infection and I believe 5-10% is commonplace, we are just not seeing it or recognising the symptoms.
“Growing a resistant variety like Annalise is a no brainer in TuYV hotspots where there is a high concentration of brassica crops grown – particularly this autumn, as the virus risk is forecast to be very high,” he adds.
The variety is also of interest outside virus hotspots, with a solid agronomic package to back up its yield and specialist trait, including a scores of 8 for resistance to lodging and stem stiffness.
Mr Walley also notes a solid disease resistance package, with score of 6 for both phoma stem canker and light leaf spot, combined with medium maturity.
“It is agronomically strong with no obvious weaknesses. We see it as our key conventional variety this year and expect to sell out of seed,” he says.
While variety choice can help boost oil bonuses next season, Mr Walley adds that growers should not to desiccate too early this summer, or risk reducing the crop’s oil content and potential returns.
With the pressure on at harvest, there is always a temptation to spray off oilseed rape to avoid being caught out by the weather or overlapping with the wheat harvest.
However, this can cut short the grain filling period when oil content is built, particularly on more backward parts of fields, which take longer to reach maturity.
“If you think you are ready, go away for a week and come back to it. If you compare a desiccated crop to one that hasn’t been sprayed, you can guarantee the naturally senesced one has a higher oil content,” he explains.
Grower utilises virus resistance to maintain oil quality
Turnip yellow virus can reduce oil content in rapeseed by as much as 3% and raise glucosinolate and erucic acid levels in the extracted product, resulting in bitter taste for the consumer if used for cooking.
This has been a concern for grower Andrew Ownsworth, who has built a successful enterprise producing his own cold pressed rapeseed cooking oil.
To minimise the risk of tainting the award-winning product he sells across Lincolnshire and the surrounding counties he is looking at resistant varieties to ensure the brands reputation for great taste remains intact.
“We have started to pick out [virus] symptoms in crops, so I want to get something in our armoury that will help control it in the future. It is all about keeping the taste right,” he explains.
This season he has tried 10ha of candidate hybrid Architect, which not only offers the protection against higher glucosinolate and ericic acid levels with its TuYV resistance, but also a high gross output of 105% in the East/West, 44.6% oil and pod shatter resistance.
It also fits in nicely with his strategy to grow a mix of conventional and hybrid varieties with a range of agronomic characteristics to spread risk and ensure the farm has enough rapeseed for the crush, whatever the season brings.
“The pod shatter is important as you invest a lot of effort and money in the crop, so it helps us protect the yield we have. There is nothing worse than the wind blowing and all the seed dropping on the floor,” says Mr Ownsworth.
John Challans, Nickerson’s seed specialist,says the pod shatter resistance should buy Mr Ownsworth about seven to 10 days at harvest over varieties that don’t have the trait, so can be extremely valuable.
“An added benefit of pod shatter resistance is that it gives farmers the option of letting the crop ripen naturally which not only increases oil content but also enhances oil flavour.”
He adds that Architect is also vigourous and winter hardy, so is suited to growers UK-wide, and has a score of 6 for the two main oilseed rape diseases phoma stem canker and light leaf spot.
“Architect doesn’t rely on single resistance genes, it has quantitative resistance [made up of multiple genes] so it’s more robust. It isn’t early flowering either, so lessens the risk of any frost damage in the spring,” says Mr Challans.