Oilseed rape performance is far from predictable and not as forgiving as some growers believe, analysis of results from Frontier’s Pure Yield Scheme suggests.

The scheme, introduced for harvest 2005, aims to drive yields towards a consistent 5t/ha and transform the crop from a mere cereal break into a highly rewarding option in its own right, says the firm’s agronomist, Edward Downing.

In return for buying all seed and inputs for the contract area and marketing the crop’s output through the firm, participants receive a £5/t premium and feedback to help maximise gross margins.There are more than 100 growers on board farming about 3000ha.

In the scheme’s three seasons members’ average yields have been 14.3%, 8.8% and 10.3% above the national average of about 3.2t/ha, says Mr Downing.“The results are beginning to show us trends on a practical farm rather than at trials level.“

One perhaps surprising find has been that cropping one year in two does not necessarily bring a penalty. Indeed the average has been slightly better than that from virgin land – last season reaching well over 4t/ha.

But the findings come from relatively few growers. Just 4% of members practised such tight cropping, while those on virgin land accounted for 12%, but the former generally had bigger acreages. “The suspicion is that they tend to know better what they are doing, especially when it comes to establishment, which is crucial.”

Another finding, somewhat against popular perception, is that yields have tended to increase with later sowing.

The result may have been slightly distorted by the dry early autumn of 2005, Mr Downing admits. “But since then we haven’t really had any autumns favouring later sowing.

“I certainly wouldn’t want people to run away with the message that later sowing is best. But you’re more likely to get lower yield by forcing a seed-bed than waiting for better sowing conditions.”

Realisation that seed rates are often too high seems to be filtering through. Scheme growers sowing below 5kg/ha averaged 3.75t/ha those above 6kg/ha only 3.31t/ha.

But within those means there have been huge ranges – 2.82-4.69t/ha and 2.79-4.64t/ha, respectively – Mr Downing stresses.“What that really shows is how important it is to match sowing rates to conditions.“