Later OSR drilling can lead to success
With this year’s later harvest comes the reminder that there is no need to panic and rush to get the rape crop in before mid-August ...
Many farms now have drills that cover large areas quickly, so it is possible to get drilling done in a shorter time frame than may have been the case several years ago,” said Liam Wilkinson, Limagrain’s oilseed rape product manager.
“The last few years we have seen milder autumns so soils are warmer, and as long as there is sufficient moisture, we have seen crops do well on farm when drilled at this later period.
“Most breeder and Recommended List trials are drilled later than they would ‘on-farm’ – which could be anytime from the August bank holiday – as the seed becomes available. What we see the following year in trial plots, are often slightly later drilled crops.”
Mr Wilkinson referred to work done by Dr Sacha White at ADAS, which showed later-drilled crops tended to be at less risk of cabbage stem flea beetle (CSFB) larvae, as there is less time for the adults to lay their eggs.
“So if you can get the crop up and away from the adults as quickly as possible, the crop has a fighting chance against the pest,” he said. “Drilling later can also help with black-grass control as it gives you enough time to create a stale seed bed.
“We find ourselves now in a position where there are fewer active ingredients to control the most difficult weeds in the whole rotation, particularly this year with the loss of Carbetamide.”
He added: “The pressure on these herbicides increases further considering the growing number of early drilled crops (if soil moisture allows), which can mean potentially bigger weeds under the canopy, as they’ll have more time to grow before being sprayed.
“By drilling later, the smaller crop can also make better use of autumn nitrogen, as opposed to a plant established in mid-August that is much larger and has to spread the nitrogen out.
“For those in Clubroot infected areas, delayed drilling also reduces the risk of infection.”
Neil Watson, Hutchinsons’ southern technical manager, agreed that drilling oilseed rape later may help avoid the peak migration of adult CSFB and reduce the impact from larvae.
“The French drill later than we do and still manage to get to 8 leaves before the cessation of autumn growth,” he said.
However, he noted that there is risk involved with drilling later, and yield potential may be compromised if the plant does not reach the eight-leaf stage. This places greater value on picking a vigorous variety.
“A backward crop coming into the spring has insufficient leaves and branching sites to fulfil yield potential. It also leaves little time for leaf area expansion before initiating floral development from the vegetative stage leaving a suboptimal canopy size to intercept light,” he said.
Mr Watson referred to data which suggested 400-600 day degree (80dd per leaf) from emergence to get to the required stage. “A vigorous crop emerging end of August through to mid-September has a good chance of achieving this, assuming sowing date being 2 weeks earlier roughly. Beyond this drilling window, however you are compromising yield.”
Mr Wilkinson said: “Industry wide there is much debate about the value of vigour in oilseed rape varieties. But with no standardised measurement for vigour, it’s very subjective.
“Vigour is not a point in time measurement, it is a reflection of the plant’s dynamic growth through the autumn and reflects the speed of growth and ability of the plant to accumulate biomass.
“Understanding how a particular variety develops and being able to create vigour values related to these, means that as breeders we are very well informed to provide advice on where a variety should be drilled.
“The very high-yielding hybrid LG Aviron is one of the most vigorous varieties, it establishes speedily in the autumn and puts on biomass very quickly, even under testing or challenging situations, and copes well with being drilled later. Ambassador also performs well in this drilling slot, as do our national listed candidates Armada and Academic.”
However, Mr Wilkinson added that it is key to commit to the crop fully if drilling is delayed. “There’s no point in putting the crop in the ground and then hanging back on nitrogen or weed control. The crop will need all the help it can get so it’s up and away as quickly as possible.”
Northumberland grower, Richard Brewis, has been drilling oilseed rape in mid-September for the last twenty years and does not believe this impacts yields.
“Rape is an integral part of our rotation, and we would normally have around 60ha’s in the ground. We had always done what everyone else did and drilled oilseed rape after winter barley, so mid-August.
“However, our heavy wet soils didn’t suit winter barley, so about twenty years ago, we made the decision to drop the barley and drill oilseed rape after wheat which would obviously mean drilling later, and we have never looked back,” he said.
“Now we aim to start drilling the rape by the 6/7th September and just keep going until it is all in.”
He added that this is weather dependent. “But even when a crop was drilled as late as the 20th September it was still decent, although this is slightly later than we would choose to go, but it does show that yield is affected by other factors other than just drilling date.”
Growing hybrids is essential for the approach, with Limagrain’s Aurelia making up the oilseed hectarage over the last three years. Last year the farm also trialled LG Wagner and plans to have a mix of the varieties this year.
The crop is established with a Simba subsoiler, followed by a power harrow drill and Cambridge roll, if conditions allow. “We aim for a rosette pan structure of about 7-8 leaves rather than height, going into the winter, although we have had fewer leaves and still managed to keep the crop.”
CSFB has not generally been an issue, which Mr Brewis attributes to the later drilling window. Last year’s early harvest meant that we drilled our rape slightly earlier than normal, in the third week of August and lo and behold, we found patches of damage that we had not seen before.”
He believes that there is a period where adult CSFB inflight is reduced – the second and third week of September. “We do get some winter rape weevil, and treat this, so perhaps that also has an effect on the CSFB,” he suggested.
“Our main challenge is keeping pigeons off the crop, particularly as the crop is smaller, for which we use a range of methods from gas guns and visual deterrents to calcium chloride to make the crop more bitter. We must also take great care with slugs.”
While some damage is inevitable, Mr Brewis does not give up on poorer or damaged areas. He explained that these areas can still reach around 75% of their full potential.
However, he noted that the system may not be suitable for everyone. “As we don’t have issues with black grass, we can start drilling wheat in the second week of September, so that can clash with drilling rape. We also have less time to get the wheat straw off.”
“Yes, there are risks to our approach – we only get one shot at getting the crop into the ground but so far there has been only one year back in 2012 when it rained continuously after harvest when we didn’t get the crop that we wanted.”
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