Late sowing into wet soils means cultivation tactics must be adapted and every aspect of autumn agronomy optimised to establish oilseed rape effectively this autumn.
Crops can be successfully established into the second half of September, but only if soil conditions are suitable and early agronomy spot on, says United Oilseeds technical manager, Richard Elsdon.
Harvest traffic may have so abused soil structure that growing a spring crop could be a better option. If compaction is set to impede rooting, severe moisture and nutrient stress could follow in a dry spell. “Even with all the horsepower in the world subsoiling horribly wet heavy clays will do nothing more than put lines through butter.”
To avoid further damage to wet, fragile soils confine subsoiling to tramlines and headlands, consider direct drilling or strip tillage if possible, and if not, subcast seed behind a tined cultivator working shallower than in previous years, he advises.
Lincolnshire cultivations expert Philip Wright agrees. “Growers are going to have to rely on the legacy of good cultivations last year. The best most can do is take out surface issues. It’s just too plastic at depth to get any meaningful benefit.”
Choose a loosening tine to lift, but not bubble soil to the surface, so blackgrass seed isn’t mixed through the profile and residual herbicides have the best conditions to work in, he advises. “Judge each field on its own merits, as there are big variations. Don’t think you can just use the same settings as last year. Dig to check if it is worthwhile, and if it is, check what you’re doing is effective.”
“Even with all the horsepower in the world subsoiling horribly wet heavy clays will do nothing more than put lines through butter.”
Richard Elsdon, United Oilseeds
Ploughing may pay, especially in high weed burdens. “Make a virtue out of necessity, by creating a seed-bed and a weed control benefit for next season too. But ensure the plough is set to bury weed seed completely.”
Sumo’s Marcus Ainley highlights the value of a narrow low disturbance point on loosening tines. Working 350mm down to fracture and lift, with minimal surface disturbance, they leave large clods and wetter soil where they are.
To level uneven and rutted ground in a one-pass operation the firm’s Versaplus drill uses a double row of cultivation discs set lightly in the ground, with large diameter wide profile press wheels gently consolidating before a pressure adjustable coulter system.
Take care with sowing depth to maximise herbicide options, Mr Elsdon continues. “Metazachlor immediately post-drilling controls a wide spectrum of weeds very well, which will be very beneficial this year. But seed must have 15mm of soil cover. That can be extremely difficult to achieve if seed is broadcast.”
Pre-cultivation glyphosate makes good sense given the massive burden of grassweed seeds. “It’s amazing what weeds get knocked out that are scarcely even visible. You leave those at your peril; once they get light and nutrients they will grow fast and be impossible to control.” If time is too tight pre-planting consider Roundup (glyphosate) in the pre-emergence mix, he adds.
Other autumn agronomy needs equal care. “Just like the British Olympics cycling team, the ‘aggregation of marginal gains’ will make all the difference in establishing OSR two weeks later than normal, especially as we’re unlikely to get another unbelievably mild winter.”
For variety choice remember the tough 2007/8 season, which highlighted the get-up-and-go of modern hybrids, such as Excalibur, Compass and PR46W21. “For sowing after the first week of September hybrids like these are essential. They have the clear edge over most pure lines in establishment vigour, ability to keep growing when the weather turns cold or dry, and capacity to recover from frost, slug and pigeon damage.”
Slug control will be paramount. “Usually rolling twice is good and three times better. This year once will be good, then get in with slug pellets, pretty much straight away. Don’t wait for the crop to come through – get your retaliation in early.”
Seed rate, based on seed number and thousand seed weight, should rise by no more than 10-15%, he adds, to avoid over-thick crops next spring. Apply 30kg/ha of nitrogen pre-sowing and phosphate and potash if indices are low, or pH above seven, risking lock-up.
Seed treatment Cruiser (fludioxonil + metalaxyl + thiamethoxam) controls early downy mildew and insect pests, and boosts seedling vigour.
If Modesto (cyfluthrin + clothianidin) is being used, add phosphite to boost downy mildew control.
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