7 July 1995

Stiff strawed rape bias claims denied by NIAB

CRITICISM that NIAB oilseed rape trials favour stiff-strawed varieties was rebuffed at the recent varieties and seeds day in Cambs.

CPB Twyfords John Blackman noted that trial plots of Nickel and Synergy were flat. He blamed NIABs policy of drilling all varieties at one seed rate.

"Every official trial is drilled at 120/sq m. In good conditions that is too thick and leads to lodging." As a result stiffer varieties lake Apex are favoured in NIAB trials, he maintains.

"This takes no account of commercial practice. In our own trials we vary seed rate according to seed-bed conditions, as farmers would do, and usually keep them standing. Varieties that yield best in trials are not necessarily the highest yielders commercially."

Mr Kightley acknowledges that hybrids appear to need a lower seed rate. "We are currently revising our approach to hybrid populations."

But he defends the single seed rate policy on other varieties. "Specialist claims for participant varieties have to be taken on an individual basis. I think our trials are absolutely vital for exposing varietal limitations. We need to see how varieties perform under regular agronomic practice, which our trials reflect. If companies want to develop variety management beyond this they will."

NIABtrials expose variety weakness, says Simon Kightley.