Spring OSR can help keep rotations on track

Spring oilseed rape could allow growers with weather-disrupted rotations return to first wheats next autumn. By Louise Impey

Having the latest Descriptive List for spring rape dominated by early maturing varieties is good news, says Senova’s Jeremy Taylor.

“If you’re growing it as a replacement for the winter crop, it will help get you back on track. The spring crop’s only in the ground for about 150 days.”

Used for patching it can tolerate the same residual herbicides as those applied to the winter crop, pigeon damage is rare and disease control usually unnecessary, adds Mr Taylor.

“That makes it cheap and easy to grow.”

While the new list is topped by a hybrid variety, Delight, there has been little interest to date in such types for spring sowing.

“Of the varieties with seed available, Ritz is the highest yielding conventional type, just behind Delight. It’s an early variety which stands well, so it’s in demand. Palladium is slightly earlier, but yields below Ritz.”

Whichever variety is chosen, check that the seed is treated against flea beetle, he advises.

Last chance for trifluralin

Once the variety decision is made, growers should do all they can to obtain the final supplies of trifluralin herbicide, advises United Oilseeds’ Richard Elsdon.

“It’s inevitable that fields destined for spring oilseed rape will have fat hen, redshank, black bindweed and knotgrass. And trifluralin is the only option for all those weeds.”

However trifluralin products may only be used until 20 March 2009.

“Check with your agronomist, but 2009 is the last opportunity to get cost-effective control of all the key weeds with one hit.”

Growers should spray off fields with glyphosate before starting cultivations to deal with blackgrass, he advises.

Pest threats

Most spring varieties come treated with Chinook (beta-cyfluthrin and imidacloprid). “But it’s only 50% effective against turnip flea beetle, says Mr Elsdon. So if we have a tricky spring, the beetle could already be there as the crop emerges.”

This means a pyrethroid spray may be necessary. “You’ll see shot holes in the leaves appearing at a rapidly increasing rate if they’re around.”

Pollen beetle is the other main threat to the spring crop, he warns. “There are treatment thresholds and they’re much lower for the spring crop, at two to three beetles a plant, than the winter one.

“This is because they move into crops from rosette stage onwards and can be chewing away at buds while the leaves still enfold them.”

The discovery of pollen beetles with resistance to pyrethroids in the south and east of England in the past two years has left growers with just one approved non-pyrethroid insecticide, he notes.

Biscaya (thiacloprid) is the only insecticide that will be effective where resistant pollen beetles are known to exist. But you must only make one application of this material, as we need to preserve it.”

Fungicides are rarely needed, as the spring crop does not get phoma, he explains. “For growers on the south coast, there may be a need for alternaria control.

“And after two bad years it’s worth checking for sclerotinia, even though it is widely believed that the spring crop flowers too late to be susceptible.”

The main requirement for nitrogen is in May and June, although a split application at drilling and then as a top dressing is normal practice. At current nitrogen prices, the optimum dressing is 100-120kg/ha, suggests Mr Taylor.

“Spring oilseed rape also tends to be more susceptible to boron deficiency than the winter crop,” he says.

  • Premiums of £50/t are on offer to growers of Nexera, a high oleic, low linoleic (HO,LL) spring rape, on a buy-back contract, says Mr Elsdon. “The oil from Nexera is in high demand from food processors as it’s a healthier alternative. The premium means growers can expect to raise their spring crop gross margins by £125/ha, as yields can be as much as 2.9t/ha.”
  • Partial salvation up north? Having been prevented from sowing any of his planned winter oilseed rape by saturated soils, Ian Bird hopes the spring crop will be among those helping him avoid too much disruption to the rotation on his land near Hartlepool. “I plan to grow about 250 acres, which will be the first time for 15 years. But I haven’t decided on the variety yet. I’m hoping I might get a high erucic contract, as I question whether anything else is really worth growing.”