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No rush for OSR sowing in dry conditions

Customer Insights
30.07.2018
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Andrew Ward OSR establishment
Delaying oilseed rape sowing until soil conditions are suitable for fast establishment can be more successful than early drilling when it's too dry, advocates Lincolnshire grower, Andrew Ward

With oilseed rape harvest nearing completion for most growers, thoughts are already turning to next season – and the challenge of establishing crops in incredibly dry seedbeds.

A good rain over the weekend has softened parched soils, but a forecast return to dry weather gives little sign of breaking the drought sufficiently for fast establishment of oilseed rape.  

Whilst many growers target to get oilseed rape sown during the first few weeks of August, Lincolnshire iOSR grower, Andrew Ward, advocates later sowing can be just as successful. In recent years, his best crops have been established at the end of the sowing window – last year well into the third week of September.

Andrew Ward

“That was exceptionally late,” he recalled, “but we have been consistently achieving over five tonnes per hectare from drilling in mid-September.” Last autumn’s 23rd September sowing still achieved over 4.1 t/ha, which was down on the farm’s long-term average, but at the upper end of the year’s OSR harvest results. 

“We certainly won’t be in any hurry to start drilling OSR this year, and will wait for better conditions,” Andrew added.

Growing oilseed rape primarily after spring barley – which he uses as a black-grass break and finds yields well on the farm’s heavier soils, with lower growing costs – means sowing is inevitably later, compared to a winter barley entry. This year the spring barley still looks remarkably green, given the season’s dry conditions.

“In retrospect we were fortuitous to have over 120 mm rain in eight days at the end of May into June – including 87 mm in one day on 3rd June,” he recalled. “At the time we thought it would be a disaster, but we are incredibly grateful now.” Harvest will likely be earlier than normal, but won’t change OSR sowing dates unless conditions improve.

Even with later sowing, the farm’s own design and build of ultra-low disturbance strip drill achieves 90%+ OSR germination, from seed rates as low as 25 to 30 seeds per m2 on lighter heath soils, up to 30 to 50 seeds on heavier soils.

With later drilling he advises more phosphate and N is required to give the plants a fast start, which he applies as a targeted 50 mm wide band directly over the seed placed between a rubber roller and DD roller in line with the cultivator legs. “The cultivator drill legs do appear to bring any available moisture up into the germination zone,” reported Andrew, “but following the drill’s double bank of rolls there is little evidence of surface movement.

“After these dry conditions we use a double press instead of rolls after the drill as a separate pass, to conserve all available moisture,” he added.

Andrew highlighted that he’s typically found Flea beetle pressure has been lower with the later sowing in September, compared to earlier drilling. He acknowledges that it might be benefitting from insect populations being spread across a wider acreage of green OSR stubbles from previous year’s cropping – a technique which is now being investigated in new AHDB research. That may also have been aided by the trend to later sowing of wheat crops for black-grass control, where t may be possible to leave OSR stubbles for longer to attract damaging pests away.

Flea Beetle feeding on OSR seedling

This autumn he has planned the normal 200 hectares of oilseed rape into the farm’s rotation, but with OSR yields having plateaued over recent years, Andrew now questions if one year in four – or three in some fields – is too tight? One of this winter’s tasks is to investigate viable options that could help to push the OSR out to one in six, and still successfully maintain the farm’s on-going battle against black-grass throughout the rotation.