Increasing levels of erucic acid (EA) have been found in oilseed rape samples over recent seasons, leading to rejections from the food oil crush market for EA exceedance and concerns among iOSR growers that more seed will be rejected at intake.
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 are further adding to growers’ fears.
Seed which 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 more than £1,000 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 while nothing has been identified in the certified seed supply, he has committed to test all supplies to ensure everything imported is within the required standard.
Erucic acid is naturally occurring in brassica plants, to a greater or lesser extent. In oilseed rape, breeders have selected the double low (00) traits which 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.
Seed which fails at the crush intake will fall into the lower value industrial rapeseed market.
Wild brassica plants can certainly have far higher levels of erucic acid, says Syngenta OSR field technical manager Georgina Wood. Charlock, for example, typically has an EA level of more than 30% in seed. Mustard and radish, increasingly grown as green manure crops, could also have higher levels of EA in seed.
“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 says variety cross-pollination – along with pollen from other brassica crops or weeds – could contaminate oilseed rape seed which 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.”
Fingers have also been pointed at growers of HEAR varieties – which have been specifically selected to retain high EA levels – with suggestions a legacy of volunteers could be carrying through into following crops of 00 varieties.
Scotland’s Rural College 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.
In Wiltshire, YEN awardwinning OSR grower Martin Smart has identified clear differences in varietal susceptibility to the effects of bifenox, when it is applied post-Christmas to target charlock. While it is 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.
Although most crops do recover, Mr Smart’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 Charlock is likely to be a problem in a specific field, Mr Smart 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.
A second consecutive season of prolonged winter conditions and delayed spring growth has reinforced the benefit of spring hybrid vigour, highlighted Mark Bullen.
"Strong early emergence is crucial to get the crop up and growing, but once again we have seen very forward autumn crops go backwards in late winter,” he said. “Establishment appears more about sowing date and conditions, rather than hybrid or conventional genetics,” he told iOSR growers.
“Varieties which use their hybrid vigour to kick-start early spring growth, such as the new SY Iowa and George, have the chance to really grow away as soon as conditions allow.”
That early vigour has been especially important this year to rapidly build the green leaf canopy which will enable crops to perform better in the relatively short growing season. Particularly when allied to agronomic techniques advocated by most iOSR growers, such as split application and later nutrition, PGR canopy manipulation and later Amistar treatments to retain green leaf for longer.
Mr Bullen says SY Iowa had good resistance to light leaf spot and an excellent rating for phoma. Its yield was delivered through a high number of pods, now recognised by YEN as essential to generate high output, as well as good resistance to pod shatter which ensured more seed could be safely harvested.