Clearfield – a growing practice

Over its five years of sales, Clearfield has grown from a niche weed control system to a mainstream management tool, allowing oilseed rape to be grown profitably where it would be difficult or impossible to grow using any other system and bringing fields back into rotation.

BASF Regional Sales Manager, Steve Dennis explains how the Clearfield system has progressed. “The Clearfield system is a combination of conventionally bred herbicide tolerance and the broadest spectrum herbicide in oilseed rape. Breeders, including Dekalb, have bred this trait into their hybrid rape varieties using normal crossing techniques allowing Cleranda (imazamox and metazachlor) to be used and so bringing a wide range of previously unavailable benefits to the rape grower.”

“This system is able to satisfy many difficulties that oilseed rape growers have - such as controlling charlock, runch, hedge mustard, or getting the crop established vigorously, particularly on stony, brashy or gravelly soils, or the dilemma of whether to apply a pre-emergence herbicide or wait until the crop is well established before making investing in a post-emergence weed treatment.”

Steve sees the Clearfield system as a single shot herbicide approach. “It controls cruciferous weeds such as charlock, runch and hedge mustard that are difficult to control in rape, as well as many other broad-leaved weeds and volunteer cereals. It offers the only true post-emergence herbicide option, targeting broad-leaved weeds between 1 and 4 leaves and volunteers between 2 and 3 leaves. No need for pre-emergence herbicides - growers can wait until they can see that the crop is established and weeds are apparent before investing in any herbicide.”

Recent market research and user interviews demonstrate that Clearfield is highly valued and being used strategically within an arable rotation. Deryn Gilbey, Dekalb NW Europe Marketing Lead, reports that as far as weeds are concerned Clearfield is spot-on. “Market research shows that 78% of growers interviewed cited charlock as their major weed in oilseed rape. This was followed by runch, mentioned by 41% of growers, poppy mentioned by 28% of growers and hedge mustard (24% of growers).”

“But I think it is what we get back from growers directly that shows just how far we have come. I quote from a grower in Lincolnshire ‘We were resigned to the fact that cruciferous weeds would prevent us growing oilseed rape on some parts of the farm. But a combination of DK Imiron CL and Cleranda has made all the difference. The system is a great management tool.’ Another grower in Yorkshire says ‘I can’t really believe how good the system is. It’s a perfect solution for serious weed problems. Using Clearfield strategically means we can get back to the rotation we want across the whole farm.’ Another grower in Somerset says ‘We’ve used Clearfield for three seasons now. It controls a wide range of weeds as well as charlock, allows us to stretch our rotation, and the varieties yield just as well as the non-CL rape for us.’ These farmers and many more are seeing Clearfield as an important part of their management practise,” says Deryn.

Dekalb OSR Projects Lead, Kuldip Mudhar says there has been massive progress in breeding Clearfield varieties. “Right at the start CL varieties were criticised as being not as high yielding as non-CL ones. This is definitely no longer the case, due to rapid progress being made by our team of breeders. Looking back, DK Imagine CL was our first rape variety to be launched and it was described on the HGCA recommended List in 2012. Yield of this first Clearfield variety was 95% as a % of the control. Now the latest Clearfield variety, DK Imperial CL, has a yield of 108% of the control – well up there with the best. It also has remarkable oil content of 46%.”

Kuldip also points out that the newer Clearfield rapes have many other desirable traits that the early varieties didn’t have and that growers want. “One of the most important traits for stewardship of CL varieties is pod shatter, as seed can survive in the soil for up to ten years. The CL varieties DK Impression CL and the newest variety DK Imperial CL both have the pod shatter resistance trait. Disease resistance is also an important management trait for growing oilseed rape in the UK. DK Imperial CL has excellent double phoma and good light leaf spot resistance, with an 8 resistance rating for phoma and a 6 for light leaf spot.”

“Another area of excellent progress in the Clearfield breeding programme is one of vigour at establishment and in the autumn. It is important that varieties can compete effectively early on. DK Impression CL has the vigorous establishment trait while DK Imperial CL has rapid autumn development.”

“All in all, the new Clearfield varieties have addressed virtually all initial concerns and stand up really well against non-Clearfield ones. They can compete as far as yield is concerned and can deliver all the traits that rape farmers are looking for. With the yield parity of modern Dekalb CL varieties and the wider value of the system beyond cruciferous weed control, Clearfield varieties could increase to 10% of the rape plantings before too long,” says Mr Mudhar.

BASF’s Steve Dennis says that Clearfield has now come of age. “The varieties bred by Dekalb show significant progress and compete with the best non-CL varieties. BASF has progressed a second herbicide in addition to Cleranda, Clesima (imazamox, metazachlor and quinmerac) with an even wider weed spectrum. But perhaps the most striking progress is in growers’ experiences. They now appreciate the full benefits of Clearfield and see it as a mainstream management system allowing rape to be grown where it couldn’t be grown before.”