WITH the removal of most of the lower yielding half of last years Descriptive List for oilseed rape and the addition of several high output new varieties, growers are spoiled for choice.
Yield ratings, from what is clearly a more limited set of trials than for the Recommended Lists, range from 110 to 98. And with NIAB advising caution over differences of less than 6%, producers could be forgiven for being confused.
"But it is surprising how consistent the ratings remain," says NIABs Simon Kightley. Seed for most varieties tested should also be available, he believes. "The UK is becoming much more self-sufficient in seed, although there is still always the option to import."
Breeders have made swift progress with the crop. "In 1993 Starlight (99) was seen as a breakthrough. It is still popular, but now one of the lowest yielders on the list."
The hybrids – Superol (110) a fully restored type and Triolo (109) a varietal association – offer good yields. But their margin over the conventional varieties is not as big as with the winter crop.
"My particular enthusiasm for them is because of their early vigour. Time and again they have established very well giving them a head start." Speedy early growth is far more important for the spring crop than it is in winter rape, he says.
Superols top earliness rating of 9, matched only by Acrobat (100) among the conventional types, will be especially attractive to growers in the north, he believes.
Triolo has the better oil content. It is also slightly taller but stiffer, though such differences are of minor significance for spring sowings. "It is very rare to see the crop lodged."
Top yielding conventional variety is newcomer Liga (106). Its 3 rating for standing power might seem a problem – next worst is 5 for older varieties Global (101) and Mars (100). "But it is not disastrous," says Mr Kightley. "The crop has remained accessible to the combine in the majority of trials. But in the north on heavy soil such extreme values should make you think twice."
Rebel (104), last years top yielder, remains a good choice, standing well and ripening reasonably early, he says. "Its oil content is pretty good, too."
Newcomer Trophy (104) is much the same story, although it is slightly weaker and there is some doubt about seed availability.
A clutch of varieties on 103 for yield include first-timer Liaison, Maskot, Star, Marinka (top yielder in 1994) and Aries, after four years still accounting for a fifth of the seed area.
Licosmos (101) has the highest oil content of all at 44% – next best is Liaison on 43.4%. "That has to be worth a bit, but as a variety it is still in the second run of choice after the hybrids," says Mr Kightley.
At this yield point growers selections are more likely to be driven by earliness, he suggests. Along with Maskot, Solar (101), Sprinter (101), Summit (100) and Melodi (100) all rate 8. Sprinter, in particular, seems to have a useful combination of earliness and stiffness to suit heavy land growers in the north.
Turnip rapes retain their overall edge for earliness. "They are still in a class of their own 10-14 days ahead of Superol and Acrobat." But their yield penalty of 15-20% cannot be ignored.