Clearfield Oilseed Rape

A crop production system combining OSR varieties with tolerance to imazamox-based post-emergence herbicides. Particularly relevant in direct drilling systems where pre-emergence chemistry is less desirable.

What Is Clearfield?

Clearfield is a crop production system (not GMO — conventional breeding) developed by BASF, combining:

  1. Varieties with tolerance to imazamox-based herbicides
  2. Post-emergence herbicides (Cleranda, Cleravo) that can be applied while the crop is growing

The imazamox tolerance allows control of difficult broadleaved weeds — charlock, runch (wild radish), hedge mustard — after crop establishment, avoiding:

  • Pre-emergence herbicides that can slow crop development
  • Yield losses from weed competition in the critical early establishment period

UK Market Growth

Year UK area
3 years before 2017 ~1%
2017 ~10%

Total UK OSR area context: fell from high of 755,000 ha (before neonicotinoid ban) to 564,000 ha (2017), then recovered to 600,000+ ha (2018, +10%).

Agronomic Advantages

In Direct Drilling Systems

  • No pre-emergence herbicide needed — avoids the timing pressure at a very busy period
  • Pre-emergence chemistry can hold the crop back, leaving it more susceptible to pest attack
  • Early vigour varieties (Phoenix CL, Plurax CL) suit direct drilling’s demand for fast, clean establishment
  • “Minimum tillage and direct drilling techniques” specifically cited in variety descriptions

Weed Control

Clearfield’s main advantage is timing — application in mid-to-late September (6 weeks after sowing) takes out weeds before they have competed with the crop:

“With Clearfield you can go in mid to late September with either Cleranda or Cleravo and take the weed out before it has chance to grow so you don’t get the yield loss.” — John Barrett, Sentry

Charlock benefit: As charlock contributes to erucic acid levels, eliminating it early also improves crop quality.

Key Varieties (as of 2018)

Phoenix CL

  • Main commercial variety in use (John Barrett, Sentry: 282 ha)
  • Only commercial variety grown by Sentry in 2018
  • High vigour, good disease package

Plurax CL

  • Stand-out variety in RDT (Rapid Development Trials)
  • Earliest to flower — 2 weeks ahead through the season
  • Highest vigour in Dan Wormell’s trials
  • Exceptional tolerance to Verticillium wilt (trials in Europe where disease more prevalent)
  • Valuable for spreading flowering risk — early + late flowering varieties hedge weather risk

Veritas CL

  • Being trialled by Sentry and Dan Wormell
  • Horizontal growth habit — particularly intriguing for weed suppression through ground cover
  • Benefits poor-establishment situations
  • Pod shatter resistance
  • Rlm7 resistance to phoma; score 7 for light leaf spot

Yield Gap Issue

Traditional Clearfield varieties delivered lower yields than top conventional varieties on the Recommended List. Second-generation varieties (Phoenix CL, Plurax CL) are specifically designed to close this gap.

Sarah Hawthorne (DSV): “We’ve learned a lot about drilling date, seedbed preparation and establishment techniques to help us mitigate against the loss of neonicotinoids, and new higher output and lower care Clearfield varieties could really make this pay off.”

Farmer Experience: John Barrett (Sentry, Norfolk)

  • Farm: Hill House Farm, nr Bungay, Norfolk — 1,400 ha arable
  • OSR area: 282 ha in 5-year rotation (rotation: 640 wheat, 282 OSR, 127 winter barley, 110 winter beans, 107 sugar beet, 92 peas, 69 spring barley)
  • Drill: 6.0m Väderstad Rapid with Rapid-Lift tool bar (direct drilling)
  • Post-drilling: rolled within 24 hours; organic manures (turkey litter, biosolids) where available
  • Key learning: early establishment critical — variety timing should match harvest date of previous crop
  • After barley (target: 7–10 August drilling): don’t want crop that establishes “too quickly”
  • After wheat (later drilling): high vigour essential for rapid clean establishment

Farmer Experience: Dan Wormell (Essex)

  • Area: ~600 ha; 80% of OSR is imazamox-resistant in 2018
  • Rotation: WW → OSR → WW → SW → beans or linseed
  • Drill: Dale Drills Ecodrill (direct drilled following light stubble rake cultivation)
  • Applied DAP down the spout at drilling
  • Clerando sprayed 27 September (6 weeks after sowing — described as “a little late”)
  • Key advice: spray at 6 weeks; timing learning curve is part of the process

Clearfield Chemistry

Product Notes
Cleranda Preferred by Wormell on heavy soils
Cleravo Alternative; less effective than Cleranda on Wormell’s farm

Apply mid-to-late September, 6 weeks after sowing.

Sources

  • [[sources/dd-issue-02]] — “Is Rape Ready for a Revival?”, Direct Driller Issue 2 (June 2018), featuring John Barrett (Sentry), Dan Wormell (Essex), Sarah Hawthorne (DSV)

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