Hybrid varieties of oilseed rape looked set to dominate the HGCA Recommended List, bringing benefits such as increased spring vigour and being more suited to later sowing. However, the 2015-16 list sees conventional, open-pollinated types fighting back with new additions offering high yields. So which is the better option for OSR growers? Both approaches have their pros and cons, here two growers argue their case.

Hybrid fan: Andrew Gloag, North Yorkshire

The autumn and spring vigour of hybrid oilseed rape makes it the clear favourite for Andrew Gloag, who farms 1,540ha of combinable cropping on mostly medium clay loams in North Yorkshire.

Some 300ha of Extrovert, Explicit and Expower is in the ground this season, in a three-year rotation with winter wheat and winter barley.

“Being in northern England on clay loam, we are looking for every way possible to ensure crops get away well in the autumn and again in the spring, which is why we favour hybrids for their vigour and ability to branch out and cover ground,” Mr Gloag says.

Having lost 400ha of oilseed rape due to poor establishment and harsh weather in 2012-13, he is all too aware of the need to get crops established well and acknowledges this does mean taking a more intensive approach where required.

For example, Mr Gloag has switched away from sowing rape directly into stubble with a Sumo-based seeder and now favours an initial cultivation with the Sumo Quatro before drilling with his 8m Vaderstad drill followed by a pass with Opico He-Va heavy rolls to ensure good seed-bed consolidation.

“We’ve tried the seeder/subsoiler-type approach in the past and while it works in good conditions, we found in many seasons there just isn’t the control over seed depth or seed-to-soil contact that you can get with drilling,” he explains.

(c) Jim Varney

Mr Gloag also favours earlier drilling and aims to get all rape sown from the second week to the end of August. “The majority of our oilseed rape follows winter barley, as it is such a good entry for the crop.”

Seed rates are kept relatively low at about 45/sq m to maximise the natural ability of hybrid varieties to branch and cover ground, but may be increased to 50 seeds/sq m where seed-bed conditions are less than ideal, he says.

“We’re typically achieving 90-95% establishment by drilling our rape and from what we’ve seen, hybrids do appear to get away quickly in the autumn and spring.”

There is also a relatively intensive approach to crop management through the season (see Agronomy approach), all with the aim of breaking the target 5t/ha crop. The five-year average yield is currently about 4.4t/ha, but hit almost 5.5t/ha in the best year, 2011.

“With oilseed rape prices and costs of production where they are, we’ve got to achieve 5t/ha crops. If we are going to break the yield barrier we are seeing in oilseed rape crops nationally, it is vital we look for ways to improve yields through every aspect of what we do.”

A final advantage of hybrids is their resistance to pod shatter, Mr Gloag says. This attribute is enhanced with the application of a pod sealant ahead of desiccation with glyphosate. “It seems to do a fantastic job in reducing pod shatter and means we’re not under as much pressure to get the crop cut when weather is catchy at harvest.”

Agronomy approach

Fertiliser

• Straight nitrogen applied to seed-bed – 30kg N/ha (maximum allowed for autumn application)
• Target spring nitrogen applied is typically about 200-225kg N/ha (split between end of February/early March and green bud stage). Application in line with the RB209 N-max limit for a 4.5t/ha crop
• 50kg/ha of nitrogen applied to pods at the end of flowering
• Yara N-Sensor used to optimise fertiliser inputs – has saved 10-15% on spring nitrogen applications in well-established crops.

Fungicides/trace elements

• Two autumn fungicides applied in October and November, with boron and trace elements
• Proline (prothioconazole) applied at stem extension, or Caramba (metconazole) if growth regulation is required
• Two flowering fungicides applied – one at early flowering, based on Amistar (azoxystrobin), another at late flowering based on Filan (boscalid)

Herbicides/ insecticides

• Pre-emergence Butisan (metazachlor) + Centium (clomazone), followed by insecticide for flea beetle, then second insecticide plus graminicide
• Kerb (propyzamide) is applied with the second fungicide application as part of the farm’s integrated grassweed control strategy.

Conventional fan: Andrew Branton, Spalding

Conventional varieties represent about two-thirds of the 280ha of oilseed rape grown annually across 1,600ha of mixed arable cropping at WD Branton in Lincolnshire.

Amalie, Picto and Trinity are in the ground this season, together with hybrids PR46W21, PT211 and an area of Clearfield rape.

“In the past we’ve probably had nearer a 50:50 split between hybrid and conventional rape varieties and, like many people, thought hybrids would be the future,” says grower Andrew Branton. “While hybrids probably will be the way forward longer-term, we’ve learnt there is still a strong place for conventional varieties.”

The biggest issue with hybrids is the cost of seed and the risk associated with establishing oilseed rape in the autumn, he says.

The predominantly Grade 2 silt land supports a variety of cropping (including potatoes, sugar beet and daffodils), but Mr Branton says moisture retention is a major challenge, which, combined with the ever-present threat of slug and pigeon damage, can seriously affect rape establishment in some seasons.

“Our biggest challenge is getting a decent plant stand established going into winter,” he says. “Recommended seed rates for hybrids are just 2.5kg/ha on the basis of their strong vigour and ability to branch out and cover ground, but that means there is physically much less seed going into the ground than conventional varieties sown at 6-7kg/ha.

“That’s a big difference and is fine if conditions are good for establishment, but it’s a big risk to take when a bag of seed costs more than a tonne of rape is currently worth and there are so many things that want to eat the crop from the outset.

“Hybrids do often demonstrate good vigour, but for us it’s a numbers game. At least with conventional varieties we have the luxury of being able to put more seed on and aren’t risking quite as much if we don’t get the establishment.”

With that in mind, the more expensive hybrids are usually reserved for the better seed-beds, he says.

Target establishment going into winter is about 20 plants/sq m, but this season nearly all crops have established well and are far above this, he says.

Agronomy is fairly similar across all oilseed rape ground. Crops are normally drilled after wheat from 12 August onwards, with a seeder unit mounted on a 5m Simba SL fitted with low-disturbance tines to avoid pulling up deeper soil clods.

Where conditions allow, land will be pressed and rolled after drilling to maximise seed-to-soil contact. A 14:14 phosphate: nitrogen fertiliser is also applied at drilling to help crops get away.

“We usually aim to get all rape in by the end of August, but have gone as late as 15 September in the past. Drilling rape that late is probably where hybrids have a part to play,” Mr Branton says.

A total of 140kg/ha nitrogen is usually applied through the season, with half going on early as soon as land will travel (end of February) and the remainder before flowering.

The fungicide strategy is normally based on an autumn phoma spray, such as Corinth (prothioconazole + tebuconazole) and two more fungicides in the spring – typically Amistar (azoxystrobin)/Prosaro (prothioconazole + tebuconazole). An autumn graminicide, insecticide plus manganese is also applied.

Mr Branton says yields are pretty similar for both conventional and hybrid varieties, at about 3.5-4t/ha as a five-year average. “Conventional varieties will perform just as well as hybrids and the seed cost is much less.

“The bigger question is whether we should be growing so much rape in general, given that the crop has almost halved in value compared with 18 months ago.”

Scientists discover reason why hybrids perform better when drilled late

Hybrid oilseed rape could be better suited to late sowing than conventional varieties, according to an Adas trial in Norfolk last year.

The Bayer CropScience-sponsored trial compared two conventional varieties (Patron and Rinker) and two hybrids (Fencer and Harper) under treated and untreated situations at different sowing dates (9 and 17 September).

It found a considerable yield penalty from late drilling, with an average yield across all varieties of 3.95t/ha, compared with 5.04t/ha for earlier-sown crops.

However, Adas’ Liz Hudson says hybrids tolerated the later drilling much better than conventional varieties, with Fencer performing best, recording a 0.49t/ha drop in yield from later sowing and the highest yield of 5.05t/ha on average.

This could be explained by analysis of green area index (GAI) and nitrogen uptake, which suggests hybrids are better at taking up nutrients and putting on growth in the autumn and spring, she says.

For example, Fencer recorded the highest GAI in November and February, at 0.482 and 0.556, respectively. Analysis showed it took up 21kg N/ha by February, some 10kg N/ha more than the open-pollinated types. The next highest GAI was Harper, followed by Rinker and Patron in February.

Hybrids also appeared better able to retain oil quality at later sowing dates, she says. Conventional varieties lost about 1% oil when sown later, while hybrids lost just 0.2-0.3%.