Spring rapeseed sales have gone through the roof after one of the wettest autumns on record left many growers’ drilling plans in tatters. Many fields were left undrilled and plenty of winter crops are unlikely to make it through the winter.

For many growers, spring oilseed rape will be the favoured replacement this spring, says David Neale, business development manager at Agrii.

“Given where rape values are, gross margins are looking very attractive. The pressure on seed supply is massive – sales are up 50-60% – and come the spring seed will be difficult to find.”

Most spring seed will be used as a direct replacement for winter rape, of which about 20% is likely to fail, Mr Neale predicts. “Sales of spring barley and wheat have also taken off, but I predict about a quarter of the failed rape area will be drilled with spring rape varieties.”

While favoured varieties are selling fast or sold out, a lot of varieties from the EU common catalogue will be available.

“Some of these varieties will not be on the Descriptive List, and some do not travel as well as others,” says Mr Neale. “Growers should also ask questions about UK data – if this is not available, find out what data the supplier is using when describing variety performance.”

Treated correctly, modern spring rape varieties can yield well, with many commercial crops making 3.8-4.2t/ha last season, says Agrii oilseed rape specialist Philip Marr.

Weight of seed

Knowing the thousand grain weight of seed is one of the most critical points, he advises. Spring varieties have a much lower value than their winter counterparts so it is easy to sow too thick a stand.

“Aim for 120 seeds/sq m with conventional varieties, 140 in poorer seed-beds, and 100-120 for hybrids, to achieve 60-80 plants/sq m. This will achieve a thick stem and about 10 laterals – the ideal canopy structure for maximum yield.”

Getting the crop to grow away rapidly after drilling is key, Mr Marr maintains. “Be patient – resist the temptation to drill in the first warm spell in February.

“Although conditions may seem favourable, both temperature and day length, vital to drive growth, are in short supply. Plants will emerge too slowly and can be rapidly crowded out with weeds.

SPRING RAPE TIPS

• Modern varieties can yield well
  
• Aim for 60-80 plants/sq m – use TGW to sow 120-150 seeds/sq m (conventional varieties); 100-120 seeds/sq m (hybrids)
  
• Don’t sow too early
  
• Apply half of N to seed-bed and other half soon after emergence
  
• Pollen beetle control is vital – start early
  
• Watch alternaria
  
• Use pod sealant to avoid damaging shattering losses
  
• Canopy care crucial in hitting the 5t/ha winter oilseed rape target

“Wait until March or early April and the crop will jump out of the ground and will compete effectively. The range of herbicides is pretty much limited to metazachlor pre- and early post-emergence, plus the dims and clopyralid. Clomazone can be used but I don’t advise it – the damage can be too severe.”

Simon Kightley, oilseed rape specialist at NIAB TAG, advises slightly higher rates – 150/sq m for conventional and 120 for hybrids.

“Growers have got much better at establishing lower populations in the winter crop, but it is too risky with spring varieties, mainly due to the small seed size. And plants do not branch nearly as prolifically due to the short growing season, so a higher number is needed to compensate.”

Mr Kightley reinforces Mr Marr’s drilling date advice, not only to keep ahead of weeds, but also to ensure plants outgrow pest damage. “Flea beetle can be a major problem in the spring crop and all seed should be treated. Be prepared to come back and spray if the crop is not moving fast. Pigeons and slugs can also wreak havoc with a slow-growing crop.”

Nitrogen addition

Nitrogen should be applied early – about half the total, 50-80kg/ha, in the seed-bed along with a similar amount of P and K depending on indices, and the rest at the two- to four-leaf stage, says Mr Marr. The crop never responds to later N applications, he maintains.

Mr Kightley advises pushing rates higher – up to 125kg/ha. “You definitely need at least half in the seed-bed – you don’t want to waste a moment when the crop is ready to go. Apply the rest once the crop has emerged – you don’t want to get caught out by a prolonged dry spell.”

Pollen beetle control is key, both men agree. Applications are usually made too late, at green to yellow bud, says Mr Marr.

“Flower buds form just four to six weeks after emergence when plants are still prostrate. That is the time to spray and be prepared to follow up fortnightly two or three times – if you wait until yellow bud the pollen has already been destroyed.”

If any beetles remain two days after treatment with pyrethroids, resistance must be assumed, says Mr Marr. “Follow up with an alternative active as soon as possible.”

Get close up and keep a close eye and spray at the first sign, says Mr Kightley. “ A serious infestation can remove a flowering canopy within days – be prepared for multiple applications – nothing is very persistent these days.”

Alternaria, which forms coalescing black spots on the pods, is the main disease concern. Botrytis can also be a problem. Several fungicides, including iprodione + thiophanate-methyl (Compass), control both, Mr Marr points out.

A pod sealant should be mixed with the fungicide spray as a matter of course, and a separate application considered between this and desiccation, he says. “Pods are very prone to shatter and up to 50% yield loss can occur at harvest in untreated crops.”

Growers who are replacing failed winter OSR with spring varieties should consider a stale seed-bed if at all possible, Mr Kightley advises. “I think there is still quite a lot of seed that was sown deeply waiting to germinate. It will come through once land is cultivated. Unless it is sprayed off, it will grow big and leafy and flower very late, which can severely affect the performance of the spring crop.”

Variety pointers

Unlike winter oilseed rape, there is some evidence of daylight developing between the best hybrids and the best conventional varieties in spring oilseed rape, says Simon Kightley.

“Top of the HGCA Descriptive List, the hybrid Makro has a gross output of 109%, 6% ahead of the best conventional variety, Shelley, which I understand will not be available this year. However, Makro is late-maturing and may not be ideal for growers needing to patch up blocks of failed winter rape and looking for the earliest possible harvest.”

Two new hybrids, Millenium and Register, on 107% and 105% for gross output, respectively, are much earlier maturing. But with only three years of relatively sparse trials data, these might be varieties to try on a restricted scale, says Mr Kightley.

The natural starting point might be the conventional variety, Tamarin (102% for gross output), he says. “It has the earliest maturity on the list and six years of trials data behind it. Another half-dozen varieties approach Tamarin for gross output, but fail to match it for maturity.”

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