Cruciferous weed seed contamination, farm saved seed and volunteers from previous HEAR (High Erucic Acid Rape) crops are the most likely sources of the high levels of erucic acid contamination detected in UK double low rapeseed in recent years, according to the latest grower intelligence.
Part of a national oil quality study conducted by leading OSR breeder, Dekalb this spring, the on-line research involved more than 160 growers from across the country responsible for almost 75,000 tonnes of annual rapeseed production.
While the majority of these report no issues with their rapeseed marketing, some 17% have experienced problems in the past two years.
A noticeably greater proportion of those growing HEAR crops in the past 10 years (24%) report such crop marketing problems, rising to 27% with those growing HEAR in the past five years.
At the same time, more than three quarters of those reporting the most serious problems use significant amounts of farm saved seed.
However, the fact that the largest proportion of those reporting some rapeseed marketing problems in the past two years use only certified seed and the vast majority of these haven’t grown HEAR for the past 10 years clearly indicates wider issues are involved.
Any erucic acid impurities in the crop are effectively dealt with at the crush to ensure all rapeseed oil for human consumption is well within the EU’s current allowable 5% maximum as well as the 2% to which this is set to be reduced within the coming year.
Even so, the supply industry is obviously concerned that up to 20% of double low rapeseed deliveries currently have erucic acid contents of more than 2% on rapid NIR intake testing and is keen to address this.
“Our study indicates a high degree of grower awareness of the issue,” reported Dekalb UK lead, Geoff Hall. “Indeed, nearly two thirds of growers are currently concerned over erucic acid impurities in double low rapeseed. And this rises to almost 90% if, as anticipated, EU oil standards for human consumption are tightened in the near future.”
With typical erucic acid contents of up to 30%, growers clearly see cruciferous weed seed contamination as the most likely route for these impurities. Farm-saved seed and volunteers from previous HEAR crops are also widely identified as likely routes.
Smaller, but still significant numbers of growers mention cross-pollination from nearby HEAR crops, mix-ups in storage, poor storage or transport hygiene and certified seed (Figure 1).
“Interestingly too, three quarters of growers identify more than one likely route for erucic acid impurities in double low supplies and almost half suggest three or more routes,” noted Geoff Hall. “This reinforces the view that multiple causes are almost certainly responsible.”
Under these circumstances, growers are advised to understand the history of the fields in which they plan to grow their double low OSR, particularly whether they may have been used for HEAR in the past.
At the same time, they are urged to have farm saved seed tested for erucic acid content and obtain analysis certificates for their purchased seed; ensure the most effective control of weeds with high levels of erucic acid content; maintain good storage and transport hygiene; and retain samples of every shipment leaving the farm in case of issues at intake.