Oilseed rape growers who shy away from drilling well into September after the experience of last season are at serious risk of throwing out the baby with the bath water, warns a leading national crop adviser.
“More managers certainly need to learn when to stop drilling winter OSR and adjust their cropping plans,” stresses Agrii oilseed rape specialist, Philip Marr. “But sowing should always be dictated by soil conditions not calendar date.
“Whether it’s the middle of August or September, if your ground is waterlogged or you can’t get good seed-to-soil contact, all our experience says you shouldn’t be planting rape. Our extensive R&D also clearly shows crops drilled in decent conditions in mid-September can
out-perform those muddled-in in August.
“This is particularly important to appreciate with the large acreages of late-maturing wheats being grown these days,” he points out. “Not to mention extreme climatic variability.
“Rule out September sowing as a gut reaction to last autumn and, in many cases, you’ll be ruling out winter oilseed rape altogether. Unless you’re prepared to bring winter barley back into your rotation in a significant way, that is.”
So how does Philip Marr suggest growers most effectively protect themselves against the risk of a repeat of this season’s crop failures and production losses?
Pointing to the major differences seen in his current i-farm demonstration plots with 45 leading and emerging varieties at Brotherton in Yorkshire, he is adamant that fast-developing varieties are the key essential.
“All our plots went in on September 28th at 40 seeds/m2 and only began emerging in late October,” he reports. “So they struggled through the winter with little more than three leaves, then suffered prolonged pigeon attack plus extreme cold and the bitterest of easterly winds around Easter in the worst early OSR season I’ve experienced in more than 30 years.
“They only came into full flower in late May so they won’t be setting any yield records. Even so, varieties with the fastest autumn and spring development are really standing out for much more even, productive and well-podded canopies than most.
“The fact these types needs 300-350 fewer day degrees to reach five leaves than the slowest developer has been an immense advantage with temperatures at the sort of premium they were last autumn and winter,” Philip Marr observes. “Also more apparent than ever has been the value of fast spring development in allowing sufficient lateral growth ahead of stem extension.
And the ability of varieties with well-waxed leaves to survive late icy blasts as well as contact herbicide damage.”
For the greatest reliability and sowing date flexibility this autumn Philip Marr picks rapid autumn and spring developing varieties like DK Excellium, DK ExPower and Excalibur as the best bets. He accepts these types may have presented difficulties with excessive growth from early sowings in 2011/12, but stresses they didn’t cause problems when sown at low enough seed rates and with robust autumn and spring growth regulation.
“While height is something we can manage, the one thing we’ve learnt from this season is that we can’t manage a crop we haven’t got,” he insists.
“With land you can be sure of sowing before the final week of August – following winter barley perhaps – a slower developing hybrid or pure line may be suitable; especially for those less confident of managing early growth. But such varieties present an unacceptable risk if sowing has to be delayed for any reason.”
So for earlier sowing or high fertility ground and a wider overall sowing window Philip Marr recommends one of the newer low biomass hybrids. Rather more upright and faster-growing than the original very short, semi-dwarfs, he never sees varieties like DK Sensei growing beyond a nice Castille-like height, making them virtually impossible to lodge.
“If you’re going down the semi-dwarf route adequate pod shatter resistance is vital,” he warns. “Stiff stems make mature crops more susceptible to shedding than those that have the flexibility to bend in the wind. That’s why we’ve found shatter susceptible semi-dwarfs can shed very badly.”