21 April 1995

Right methods realise benefits of hybrid rape

By Andrew Blake

HYBRID oilseed rape offers significant yield advantages over conventional varieties – but growers will have to re-assess their husbandry to achieve them.

Applying normal methods to so-called "variety association" hybrids could cause disappointment, according to Mike Pickford, oilseed rape consultant with CPB Twyford – the company stemming from the acquisition of Twyford Seeds by CPBs parent company AGC.

More importantly, it could tarnish the overall image of promising hybrids such as the firms Synergy, an 80:20 mixture of a male-sterile Samourai/Falcon cross and Falcon pollinator.

In regional trials last year Synergy is said to have given 12-30% more than the mean of the NIABs top yielding recommendation Apex and the more established Falcon, depending on site. In Scotland the range was 12-18%. The results came from heterosis or hybrid vigour creating bigger, faster-growing plants with stronger stems and bigger seeds, explains Mr Pickford.

S factors

But to allow the full benefits of that vigour to be expressed, growers will have to observe the four "S factors" – seed-bed, seed rate, sulphur and spraying for pollen beetle.

Not listed on the Common Catalogue, the "variety" is in its second year of official UK trials, technically under an EC authorised experiment covering mixtures. To ensure it fulfils its promise, the firm plans to sell it through a "controlled release" of "several 1000ha" to experienced growers prepared to give it the necessary professional attention.

It is essential to avoid excessive early growth of the vigorous male-sterile plants. Seed set can be poor if they are allowed to smother the pollinators, explains Mr Pickford.

Sowing too early – before mid-August – could lead to trouble. But for the crop to get away well once sown, fields should be fine, firm and even, he says. "You must not cut corners with seed-beds." Seed should be drilled, not broadcast, he adds.

Conventional rates out

Conventional seed rates are out. Instead the advice is to sow as little as 3.1-3.4kg/ha, providing 70 rather than the more conventional 90-100 seeds/sq metre. The aim is to achieve a post-winter population of 40-50 plants/sq metre. Drilling thicker risks competition between the hybrid plants and the pollinators. Because of this, hybrid seed will probably be sold in unit area packs akin to those for maize.

To maximise pollen production, sulphur – 80-120kg/ha of SO3 (32-48kg/ha of S) – is a "must" in hybrids, says Mr Pickford. So too is spraying for pollen beetle.

&#8226 More widely available is CPB Twyfords provisionally recommended conventional variety Nickel – joint highest yielder with Apex but with better light leaf spot resistance.

"Its been described as weak-strawed," says Liz Williams, the firms head of oilseeds breeding. "But we dont see this weakness as a disadvantage because of its canopy structure." The scope to cut inputs has given Nickel the best gross margins, both treated and untreated, in three years of official trials, she says.