Clearfield oilseed rape was originally introduced into M.E.S Dart & Partners 1000 ha arable rotation near Wallingford, Oxon to deal with charlock and runch problems. But five years on it is proving of much wider value for manager, Mark Oldroyd and his assistant, Jack Bedlow.
Indeed, vigorous DEKALB Clearfield hybrids are an important part of their determined effort to combat the growing establishment challenges facing the crop.
“Oilseed rape is a valuable break in the five year wheat-based rotation we run across much of our ground,” explained Mark. “At 4.5t/ha there’s nothing else to match it in margins and it spreads our workloads nicely. We also find it useful in keeping on top of grassweeds.
“However, reliable establishment is always the key with OSR. And this has become so much harder to achieve in recent years with the big increase we’ve seen in flea beetle problems from the double whammy of neonic withdrawal and pyrethroid resistance.
“We saw yields pegged back to barely 3.5t/ha last harvest. And this season, for the first time ever, we’ve had to write off part of our 80ha crop. Flea beetle pressure means the establishment recipe we’ve followed for a while now is no longer working. So we’re having to seriously rethink our approach in order to keep OSR-growing viable.”
Most of the business’ oilseed rape is currently sown in a single pass with a Claydon Hybrid drill following winter or spring barley. All the straw is baled for the 650 dairy cows plus followers run in parallel to the arable enterprise, and the ground straw-raked to stimulate a grassweed and volunteer chit for pre-planting control.
Drilling typically starts in mid-August with home-saved conventional seed. The leading Clearfield hybrids, DK Imperial CL and DK Impressario CL are reserved for later drilling – often well into September.
“The superior vigour of these Clearfield hybrids is impressive,” Mark commented. “Despite the disadvantage of later sowing, they’ve always yielded on a par with our conventional varieties. What’s more, they definitely grow through flea beetle attack much better in the autumn and bounce back from it more strongly in the spring.
“Their particular ability to recover has become essential for us,” added Jack Bedlow. “At the same time, they don’t need a pre-em and we can be sure of avoiding any erucic acid contamination from either cruciferous weeds or previous volunteers.”
With later sowing to avoid the peak of flea beetle emergence a key element in the planned programme to adapt the establishment regime, Mark and Jack see the particular vigour and recovery abilities of their Clearfield varieties standing them in increasingly good stead.
Alongside this they are looking to reduce soil movement further while improving moisture retention and sowing depth consistency by adapting the Vaderstad Tempo L drill they use for maize planting. This will also give them the ability to move to wider rows and even sow a companion crop between them to either confuse or divert flea beetles.
Improved consolidation for better seed-to-soil contact with heavier rolls is on the agenda too. As is a starter fertiliser in place of the dairy slurry or FYM often applied immediately ahead of the OSR; something that can get in the way of establishment by adding too much wetness and extra biomass.
“Putting our rape in after spring instead of winter barley is another opportunity,” said Mark. “We find the oats and vetch cover crop we grow ahead of our spring barley and graze with overwintered ewes from Wales these days leaves the soil in much better condition.
“We’re also considering putting 6m margins around our OSR down to annual EFA pollen and nectar mixes,” noted Jack. “The headlands always tend to be the most difficult to establish as well as especially vulnerable to pigeons. So yield mapping shows they’re invariably the areas that pull our performance down. Of course, taking them out of production will add to our environmental improvement efforts too.”