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Arable

Clearfield OSR use is growing t DK Imperial CL is now the sixth most widely grown of all winter rape varieties. u Agronomist Ben Burrows (left) with farm manager Michael Maxwell.

From less than 1 per cent of national plantings in 2014/15, Clearfield OSR has expanded to make-up more than 10 per cent of this season’s 600,000ha national crop, according to the latest results from the benchmark Kleffmann Group WOSR Amis farmer input panel revealed at an industry briefing this spring. Data from the 400-strong panel, carefully selected to be representative of British producers, shows the 2017/18 Clearfield area more than doubling for the third year in a row. Indeed, it is now larger than national areas of High Oleic Low Linolenic (HOLL) and High Erucic Acid Rape (HEAR) combined. “Clearfield OSR has become firmly mainstream,” said breeding company Dekalb’s Mark Shaw (right). “The Kleffman Amis data also shows a third more farms using the system this season than last, with double the number growing Clearfield varieties alone. What’s more, the market leading variety DK Imperial CL is now the sixth most widely grown of all winter rape varieties.

Tolerant of residues “Being tolerant of SU herbicides, Clearfield varieties are well able to cope with any residues that might be present following a winter wheat crop,” pointed out BASF’s field crops manager, Dave Marris (right). “This and their hybrid vigour gives them a valuable edge in getting the rapid and reliable start vital with winter OSR in the face of multiple

establishment challenges. The Clearfield herbicides, Cleranda (imazamox + metazachlor) and Cleravo (imazamox + quinmerac) also remove the widest range of weeds of any single product on the market. “As well as controlling most major broadleaves and both cereal and OSR volunteers – which can be invaluable for accurate canopy management – they are highly effective against problem crucifers like runch, charlock, shepherd’s purse and hedge mustard,” said Mr Marris. “Together with any HEAR volunteers, these are known sources of erucic acid, making the system good news for growers concerned over penalties or rejections where rapeseed levels exceed 2 per cent.” As a true post-emergence system, of course, Clearfield is highly flexible, ensuring the best herbicide activity regardless of seedbed quality or establishment method at any time from one to four true leaves of weeds and volunteers. However, it is important to note that Clearfield herbicides can only be used on CL varieties, warned Mr Marris. “Conventional varieties have no tolerance and will be wiped out.” Alongside the system’s much wider grower value, impressive

improvements in the all-round performance of Clearfield varieties also underpin its increasing popularity. “The first variety with the trait to join the Recommended List in 2013/14, DK Imagine CL was a good 5–10 per cent off the pace in its gross output,” pointed out Dekalb technical specialist, Will Vaughan-France. “It was also a shatter-susceptible semi-dwarf with average disease resistance ratings and less rapid autumn development than our mainstream hybrids. “Since then yields, oil contents, traits and agronomics have all come on by leaps and bounds. So much so that today’s DK Imperial CL has a two year average gross output midway between farmer-favourites, DK Extrovert and DK Exalte in our national trials. “It shares strong phoma and light leaf spot resistance ratings with these mainstream varieties, together with our vigorous establishment, rapid autumn development and pod shatter resistance traits. This all-round strength has enabled it and current stablemates, DK Impression CL and DK Impressario CL to deliver levels of 2017 farm performance every bit as high as today’s leading double lows.”

Back on track Clearfield oilseed rape is reinforcing its potential as a mainstream OSR choice on a Hampshire estate, where it is being grown on a field with a history of charlock infestation that almost wrote off the last crop of OSR in 2013. “We said we would never grow oilseed rape in that field again,” said farm manager Michael Maxwell, at Preston Farms, Preston Candover near Winchester. “It was so bad our combine driver asked me if I really wanted him to cut it.” After a discussion with his agronomist, Ben Burrows, however, he opted to take advantage of the Clearfield system to maintain the estate’s 5-year rotation on the 27ha field this season; a decision that proved right despite mid-September sowing into decidedly poor, wet seedbeds. “We subcast the DK Imperial CL into the flinty clay loam ground much later than we’d planned following

serious winter barley harvesting problems,” Mr Maxwell explained. “Our converted Flatlift cultivator did a reasonable job despite the conditions, sowing around 55 seeds/ m2 in 50cm bands. “Helped by the variety’s vigour, an open autumn and far fewer pigeon problems than we were expecting, the crop established well and came out of the winter with scarcely a weed in sight. I have no doubt that if it wasn’t for Clearfield, it would be a complete mess.” Clearfield crops account for around 11 per cent of the OSR area currently being overseen across southern England by independent agronomist, Ben Burrows and his colleagues at Hampshire-based Crop Management Partners (CMP). “We find the system very effective in helping growers deal with problem areas on their farms,” he said. “The top reason for us is ease of controlling cruciferous weeds which would otherwise make OSR unviable. Using it we’re able to achieve very reliable control of even quite large weeds. “The Clearfield system gives us the opportunity to omit preemergence herbicides which can slow down emergence too. Every bit as importantly, it also means we can wait and see how the crop establishes before spending large amounts on agrochemicals.” Mr Burrows also values the broadspectrum of weed control offered by Clearfield herbicides, and the ability to sequence them with other postemergence herbicides, depending on problem weeds. The Clearfield crop at Preston Farms received no pre-emergence herbicide, except headland Springbok (dimethenamid-P + metazachlor), which is used on all of the farm’s 162ha of OSR to boost cranesbill control. It then received propaquizafop + insecticide in early October, followed by Cleravo + Dash in late October, then propyzamide a month later. “We chose Cleravo to keep on top of poppies, in particular,” Ben Burrows pointed out. “It has made an excellent across-the-board job of our weed control as well as dealing extremely effectively with a large charlock population.” ■

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