Oilseed rape Clearfield varieties promise
the best of both worlds • Straightforward control of weeds • Decent yields and disease resistance • Helps crop meet erucic acid limits
M
ore growers are trying Clearfield oilseed rape varieties to combat dif-
ficult weeds – with increased con- trol against charlock, hedge mus- tard and runch overcoming any yield concerns.
The Clearfield OSR system uses conventionally bred hybrid seed varieties resistant to BASF’s Clearfield herbicides – making post-emergence broad spectrum weed control much easier. But some farmers are hesi-
tant to adopt the system because yields of Clearfield varieties have sometimes been lower than the output achieved by non-Clear- field oilseed rape. Yet that is not always the case now. “That may have been the case in the early days of development but no more as the modern gener- ation of Clearfield varieties have shot up in terms of yield,” says Neil Groom, technical director for Suffolk-based Grainseed. All weeds and volunteer rape can be controlled by applying BASF herbicides such as Cleran- da (imazamox + metazachlor) and Cleravo (imazamox + quinmerac) to Clearfield varieties post-emer- gence when weeds are at 1-4 true leaves.
Mr Groom says: “This means growers can use Clearfield as a management tool, bringing fields back into rotation and allowing rape to be grown profitably where it would have been difficult or im- possible to grow using any oth- er system.”
Performance NIABTAG conducts independent Clearfield trials to assess varie-
ty performance on behalf of mem- bers. These trials are now in their third year and took place across three sites in Norfolk, Kent and Herefordshire during 2017. Grainseeds variety Aquarel
CL was the top yielding Clear- field variety with a yield of 103% – equivalent to 4.26t/ha with 4.68t/ ha gross output. In Norfolk in 2016, it yielded 4.3 t/ha or104% of the site mean with an oil con- tent of 46.3% – some 0.5t/ha above some other varieties. The company’s Decibel CL was the second highest yielding vari- ety with 102% (4.35t/ha or 4.62t/ ha gross output). “If growers want
all the advantages of the Clear- field system plus yield, then they should be choosing either of these two varieties,” says Mr Groom. “Growers also are much more
aware and concerned now about erucic acid levels in rapeseed loads and it is thought that this may come from cruciferous weeds such as runch, wild radish, char- lock and hedge mustard. UK and EU legislation sets a limit of 5% erucic acid in food- stuffs. These limits may be tight- ened in the future. At the moment growers face significant price penalties when oilseed rape loads are between 2% and 5% and crops may be rejected if over 5%. Controlling brassica weeds us- ing Clearfield is the best way to avoid this potentially costly risk. Mr Groom also points out that Es Aquarel CL is very early ma- turing like Es Alegria (yet it still produces high yields with high oil content levels of 44.7%). This means the crop can be in
the barn well before other Clear- field varieties, helping with heavy workloads at harvest, says Mr Groom.
It has high resistance to lodg-
ing (8), stem stiffness (6.3) and excellent multi-gene resist- ance to disease, with a 7 rating against Phoma stem canker and a 7 against light leaf spot. It has good autumn vigour and good pod shatter resistance.
Questions over output are no longer a concern, says Neil Groom The Clearfield system
The Clearfield production system for oil- seed rape combines vigorous, hybrid varie- ties with innovative BASF herbicides which are effective against a range of weeds. Clearfield varieties have been developed using traditional plant breeding techniques and are tolerant to the imidazolinone group of ALS inhibitor herbicides. This makes weed control easier.
A number of Clearfield varieties are avail-
able from a range of breeders. They provide a range of growth habits, disease resistance, and for many, yields comparable with main- stream varieties. “Clearfield gives a ‘rapid start’ effect,” says BASF business development manager Clare
Tucker. “This early vigour allows fast and even establishment in the autumn, which is so critical to mitigate the effects of challeng- es such as cabbage stem flea beetle attacks. In addition to hybrid vigour, varieties are tolerant of possible residues from sulphonyl urea (SU) herbicides used in previous cere- al crops, allowing the plants to get off to the best possible start.” Both Cleravo and Cleranda offer very sim- ilar broad-spectrum, weed control and can be used as a one-shot option. Where high popu- lations of weeds that get big quick are antic- ipated – such as crane’s-bill, poppy or may- weed, Cleravo also allows the option of an early application of metazachlor or Springbok.
Es Decibel CL has excellent autumn vigour, increasingly im- portant now neonicotinoids are banned. It has an 8 rating for Pho- ma and a 5 for light leaf spot, an 8 rating for resistance to lodging and 5.9 for stem stiffness. It has a high oil content of 44.1%.
Clearfield gives a ‘rapid start’ effect – Clare Tucker
JULY 2018 • ANGLIA FARMER 33
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