20 June 1998


Hybrids without pain are well within the reach of most growers. This could be the time to give them a try, suggests NIAB.

FOR little more than an extra £10/ha seed cost, hybrids can provide returns at least £30/ha higher than the best traditional rapes.

Thats the conclusion of Simon Kightley, NIABs oilseed variety specialist, who is also confident there is no real need to treat hybrids any differently from traditional rapes – apart from heeding the breeders recommendation to reduce seed rates.

Mr Kightley draws his evidence from other trials – FACTT project work – which show hybrids as a group responding to inputs in much the same way as traditional inbred rapes.

"Growers must ensure adequate early nitrogen is available to support vigorous spring growth, but fertiliser response curves suggest that they dont need more fertiliser," he says. "Additionally, they dont respond any differently to fungicides, but varietal associations do need good pollen beetle control.

"Hybrids may be slightly more sensitive to sowing date and hence best drilled at conventional times in late August to early September," he suggests.

"Bearing in mind the lower seed rates and the need for a well established ground cover, later drilling in mid-September may not always be advisable."

Finally, provided they are sown at the lower seed rate recommended by the breeder, hybrids will also stand well, so risks of lodging are small.

Two years of EU-wide trials – funded in the UK by the HGCA – where varietal associations such as Synergy and Cocktail are grown in blocks well away from other pollen-providing rapes, show where the extra yield potential can come from.

According to Mr Kightley, male sterile hybrid plants in the varietal association grow more vigorously, are taller and better branched than a traditional variety used as the pollinator. As a result they produce more pods; on average the sterile hybrid has 53% more pods than pollinator plants taken from the same plot.

At the same time, there is little difference in the proportion of flower positions that produce pods. Sterile hybrids had 66% pod set, compared to pollinators at 70%. This trend for fewer pods is backed up on-farm where often the early formed male sterile pods are lost – something which can cause concern when first seen by growers.

While there are fewer seeds per pod, male sterile plant seed size is around 20% higher than the pollinator variety.

NIAB is growing varietal associations this year either in separate trials within the same field surrounded by a good barrier block of a commercial varietal association, or in buffered blocks within the same trial.

Mr Kightley considers conditions so far this year have been ideal. Frosts have been rare and the exceptionally wet weather of April should have provided rapes with plenty of nutrients.

"Provided growers have kept on top of pollen beetle on Synergy and control any diseases, and we get a reasonable harvest, I would expect to see hybrids open up a bigger gap at the top of the Recommended List," he says.

Of the hybrids currently available, Mr Kightley favours the restored varieties such as Pronto over varietal associations such as Synergy. "Restored hybrids tend to be more even in pod set and pod development," he says.

Some concerns remain over seed rate. In official trials, with Synergy sown at conventional rates of 120 seeds/sq m, and at the 60 seeds/sq m advocated by the breeder, the higher seed rate has tended to produce 2-3% higher yields. "However, with much better moisture availability at flowering this year, I would not be surprised to see this trend reversed, with the low seed rate producing the best yields of all."

High seed rates are not financially viable on-farm because of the high seed cost, but agronomically there are disadvantages too. The higher seed rate doesnt allow the hybrid to grow to its full potential. The pollinator plants in a varietal association could be swamped out and fail to provide adequate pollen.

This year two more coded hybrids are up for recommendation by NIAB/SAC. From CPB Twyford comes a varietal association with a difference. This time a fully restored hybrid – Artus – is used as the pollinator. "This means that the crop is 100% hybrid and reduces the risk of crowding out of pollinator plants in a varietal association mix where a less vigorous traditional variety is included," he says.

Cargill has a 3-way hybrid where the seed segregates into a 50:50 mix of pollinator and male sterile. With every other plant supplying pollen, this has also done very well in trials so far, but the mix is important as the two components have very different levels of glucosinolate in their seed and the blend has to meet the low levels needed by the crusher.

So, what is Mr Kightleys advice for growers this autumn? His personal preference is a restored hybrid, but equally he recognises that SAC colleagues in the north have seen very good results with Synergy. "I favour Pronto, which is marginally earlier and slightly stiffer stemmed than Artus."

Hybrids should take up to a third of the acreage and be backed by a mix of established varieties. Of these, Apex remains the favourite on-farm and is still unchallenged for standing ability, but there is a lot of new material with higher yields on the Recommended List.

"With Agenda 2000 beckoning, it is perhaps time to look a bit harder at variety, disease and fungicide interactions and place rather less emphasis on ease of combining."

Main: Follow low seed rate recommendations and hybrids will stand well – Simon Kightley. Inset: Even and bigger pods (right) mark out Pronto against varietal associations such as Synergy (centre) and even new composite hybrids (left).

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