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Acid test for OSR future

Stewardship
12.05.2018
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Whilst the causes of high levels of Erucic acid in OSR oil have not yet been pinpointed, home-saved seed, volunteers, HEAR varieties and weed contamination have been implicated
Whilst the causes of high levels of Erucic acid in OSR oil have not yet been pinpointed, home-saved seed, volunteers, HEAR varieties and weed contamination have all been implicated

Increasing levels of Erucic acid have been found in oilseed rape samples over recent seasons, leading to rejections from the food oil crush market for EA exceedance. And, with EU proposals to reduce the acceptable level of EA in oils and fats for food from 5% to just 2% for the 2018 harvest crop, iOSR growers are concerned that more seed is set to be rejected at intake.

Seed that fails at the crush intake will fall into the lower value industrial rapeseed market, and is likely to incur punitive handling and re-distribution charges – potentially cited as up to £40 per tonne, or over £1000 a lorry. For crushers there is the risk of factory contamination and, with levels for oil used in baby food even more stringent, a threat to the food oil market.

The problem is that no one can be sure why Erucic acid levels appear to be rising? But somewhere in the production cycle contamination is occurring.

Seed breeders have been rigorously checking supplies, with Syngenta OSR Seed Manager, Mark Bullen, reporting that whilst nothing has been identified in the certified seed supply, he has committed to test all supplies to ensure that everything imported is within the required standard.

Erucic acid is naturally occurring in brassica plants, to a greater or lesser extent. In oilseed rape, Mark pointed out that breeders have selected the double low (00) traits that have low Erucic acid and low glucosinolate levels – typically below 0.5% and well within the Federation of Oils, Seeds and Fats Associations (FOSFA) 2% contract threshold.

Wild brassicas

Wild brassica plants can certainly have far higher levels of Erucic acid, pointed out Syngenta OSR Field Technical Manager, Georgina Wood. Charlock, for example, typically has an EA level of over 30% in seed. Mustard and radish, increasingly grown as green manure crops, could also have higher levels of EA in seed.

OSR growers should be aware of the risks of cross contamination from weed species and wild brassicas, warns Georgina Wood

“Where other brassicas are occurring in oilseed rape crops, either as volunteers from previous rotations or carried in by wild bird feeding, for example, they are difficult to remove from the crop as weeds,” she advised.

“And where they mature at the same time as the OSR, it is virtually impossible to clean the weed seed out from the crop, if the sample has a similar size.”

Georgina also pointed out that variety cross-pollination - along with pollen from other brassica crops or weeds - could contaminate oilseed rape seed that growers may be considering using for home-saved seed – which would impact on the following season’s harvest, she warned.

“It would be good practice to have farm-saved seed checked for its EA level before sowing, to ensure it meets the standard of certified seed.”

Producing clean, weed free crops from certified seed known to be low in Erucic acid content could minimise issues at harvest, she advocated. 

Producing clean, weed free crops from certified seed known to be low in Erucic acid content could minimise issues at harvest

HEAR dangers

Fingers have also been pointed at growers of HEAR varieties – which have been specifically selected to retain high EA levels (see panel) – with suggestions that a legacy of volunteers could be carrying through into following crops of 00 varieties. The SRUC specifically warns growers to be wary of future crop contamination. The HEAR premium, of around £30/tonne, is acknowledged as necessary to cover the cost of potentially lower yields and the increased cost of cleaning up ground after growing the crop. 

Investigation project

A new investigation launched by the AHDB this spring is seeking to evaluate the Erucic acid testing procedure from crushers’ intake. The project, which is due to report in late autumn, also aims to assess the influence of other crop and weed species on the fatty acid profiles of OSR, as well as the contribution of cross-pollination and other effects of in-field volunteers. 

Charlock challenge

In Wiltshire, YEN Award winning OSR grower, Martin Smart (below), has identified clear differences in varietal susceptibility to the effects of bifenox, when it’s applied post-Christmas to target charlock. Whilst it’s the best option available, under a grower’s own risk SOLA, it does tend to remove the protective leaf wax coating, particularly if the crop is under any stress, such as nutrient, weather, rooting or moisture.

Martin Smart - iOSR Wiltshire grower

Whilst most crops do recover, Martin’s independent variety trials have shown there can be a severe check in growth, and some varieties are hit harder than others – which could also knock-on and impact other spring activities for top dressing and spraying.

Where growers know that Charlock is likely to be a problem in a specific field, Martin advocated they could select varieties known to be more tolerant to the herbicide treatment, or even consider not growing OSR in that field and make efforts to clear up the weed burden first. 

Why do we grow high Erucic Acid varieties?

Erucic acid is a valuable commodity for some industrial oil applications. Once extracted and converted to erucimide, the high EA content oil has a very high friction point, which makes it extremely good for bearing lubrication and some premium applications in printing. Its other key use is in plastic packaging, where a microscopically thin layer applied to polythene bags gives them the necessary ‘slipiness’ to open easily. It is one of the few oils approved for use in food packaging. HEAR varieties typically have 55-60% EA content in seed, with the processing and conversion to erucimide at a plant in Hull.