With the UK harvest almost a week ahead of normal, many growers will be looking to get oilseed rape crops established. However, Liam Wilkinson, arable development officer at Limagrain UK, is warning that farmers should wait until moisture levels are correct.
“Whilst some areas have seen some rain recently – many have not had any – and even where it has rained, it needs to be a serious amount to restore moisture levels to where they need to be to sustain a rapidly emerging rape crop,” he pointed out.
Not much rain is forecast for the start of August, though many will be worrying about compromising the crop by holding off on drilling. Mr Wilkinson’s advice, however, is that holding off will not compromise yield and that establishment should be guided by seedbed conditions rather than calendar dates.
“It is possible to get good yields from later drilled rape when sown into the right conditions. In fact, they often outperform some of the earlier drilled crops – and many later drilled crops have been winners in the YEN awards!” he said.
“Last year we saw crops of LG Antigua drilled mid-September up in the Lincolnshire Wolds achieve yields of over 6 t/ha, so there is definitely high yield potential for crops drilled into September in the right conditions.”
“Choosing the correct variety for this drilling window is key to success. If you are drilling in September, the focus should be on speed of autumn growth and vigour, so hybrids are the first choice because they are quick to get going and they accumulate biomass very quickly,” he added.
“Vigour is also important to get the crop established and putting roots down, but the speed of development for reaching over wintering biomass as quickly as possible is key. A variety in this situation will also benefit from a canopy in order to withstand potential pest problems, as well as harsh winter conditions.
“Tried and tested varieties such as Aurelia and Ambassador have performed consistently in this slot, both on farm and in trials for a number of years now.
“More recent additions of LG Aviron, LG Auckland and LG Antigua to the AHDB Recommended List strengthens the variety options available to growers when drilling later than planned.”
Seed rate
With vigorous varieties, seed rates should target 25-30 plants per m2, instead of the usual 50 plants. Mr Wilkinson also recommended that growers assess seedbed conditions and adjust seed rates accordingly to account for losses, particularly if conditions deteriorate.
Limagrain’s 2021 OSR Established Scheme
The 2021 Establishment Scheme provided useful insights into when crops are drilled, with drilling dates tracked against the weather at the time. The data showed that drilling in dry conditions resulted in subsequent crop losses while crops that had rainfall around two weeks from drilling were more likely to survive.
“This data reinforces the need for moisture when drilling oilseed rape for successful establishment, as this allows the crop to germinate and grow up and away from CSFB as quickly as possible,” Mr Wilkinson added.
Neil Watson, technical manager at Hutchinsons, shared his views on why moisture is so fundamental. He said that oilseed rape goes through a two-stage process before emerging; the first of which relies on the seed taking up 40% of its own weight in moisture before germination. The second stage of repair and stabilisation requires more moisture.
“How often have we seen seed that has started to germinate but then withers away through lack of soil moisture, before completing emergence? So sufficient moisture is needed in the soil to start the process and then more rain following drilling, to ensure there is sufficient moisture for the crop to emerge.”
