Spring forward for iOSR growers’ agronomy decisions
iOSR growers from across the UK highlight some of their management decisions in response to the late start to flowering, and how they now intend to look after their crops going forward.
For Lincolnshire iOSR grower, Chris Baylis (below), crops were only a yellow haze in mid-April, compared to mid-flowering at the same date last year. He highlighted that, despite significant Cabbage Stem Flea Beetle pressure delaying growth last autumn, most of the Sutton Estate’s OSR area had grown strongly through the winter; but it was hit extremely hard by the prolonged cold weather in March.
NDVI images of the crop in February and then in March showed it had physically gone backwards, and was still struggling to regain the lost green leaf area even by mid-April.
However, whilst the crops are late, they are even, he reported. “A growth regulator fungicide at early stem extension seems to have held back the main raceme from bolting under stress, enabling the side branches to develop at the same time,” he said.
As a result, Chris believes that flowering could be shortened this season, which will be beneficial to the crop and reduce the risk if Sclerotinia, especially if conditions stay dry for a period. “However I am told that we had similar weather patterns in 1976, so we have been forewarned,” he added.
Chris did opt to adjust fertiliser programmes on three-quarters of the OSR area, to compensate for the loss of in GAI during March. “Normally we adopt a two stage programme - with the first pass for canopy development being based on GAI’s, then the final pass applied as late as we dare, ideally at yellow bud, for yield.
“This year, however, we added an additional fertilser pass to compensate for the loss of canopy,” he reported.
In the Cotswolds, Martin Parkinson of the Cotswold Farm Partnership, also split N applications into three passes this year, in an effort to increase the green leaf area. The final pass was some three weeks later than last year, and would have been delayed further except pressure of field work dictated the application had to go on.
Martin (avbove) highlighted that only very forward fields had received any growth regulatory targeted treatments. “In some fields the main raceme has raced away, and seems to be missing the leaf area which would help build yield later,” he reported.
Delayed by the extreme cold weather experienced in the Cotswold, Martin reported seeing no signs of flowers on his OSR even by the third week of April, but was confident that with a few days sunshine they would start to appear. The good news from the cold weather was that the propyzamide herbicide treatment had been particularly effective, especially targeting the heavy Charlock weed pressure, he pointed out.
The effects of farm topography and exposure to the elements on OSR growth was highlighted by Derbyshire grower, James Chamberlain, reporting oilseed rape at yellow bud and flowers opening in mid-April. Despite being further north, the farm is generally more sheltered.
Shoots shot away
However, like Martin Parkinson, he reported it was mostly the main stem that had shot away, with very variable side branching in the uneven crop. “It’s a result of the prolonged wet spell and not being able to apply a growth regulator because of the weather,” he said.
James (below) pointed out that he is likely to go with a more robust flowering spray this season, aiming to apply at the early to mid-flower timing, if he can get the application on.
Fertiliser applications have also been delayed by the field conditions, but with the later flowering crop the timing should still be fine to influence yield on the post-flowering period. “We just need a kinder weather period post-flowering to get a reasonable yield,” he added.
The change in fertiliser application timings also saw Norfolk iOSR grower, Chris Eglington, shift to apply less early N and more put on at the later timings.
In the eastern counties he had felt the full force of the Beast from the East, with the second hit causing more damage - when the crop had less snow cover to protect from the cold winds. However, whilst the green leaf area had certainly gone backwards and plants lost size, he did report achieving good success with a PGR application having a big effect this year.
“After using a PGR to hold back the main raceme we have lots of side shoots developing at the same time,” reported Chris Eglington.
Across in the Northamptonshire, Ian Matts of Brixworth Farming (below), added that most of his OSR growth had been the main raceme, but he was hopeful that the side shoots would develop quickly, particularly as plants had the chance to pick up more of the late applied nitrogen.
One positive aspect of the cold weather has been that his crops have come out of the winter relatively clean of disease, with no recent fungicide treatments required. Although flowering had only just begun to emerge in mid-April, Ian pointed out that last year was particularly early and that, in reality, it was probably only a week to 10 days behind average, with plenty of time to recover and compensate well enough.
Beetle hits near miss
For most of the Syngenta iOSR growers’ group, Pollen Beetle had not been seen as a serious issue, despite the crop being checked at green bud stage for a prolonged period. Cold weather had perhaps been detrimental to the beetles as well as the crop.
However, in Norfolk, Chris Eglington (below) commented that Pollen Beetle activity had been identified at above the 25 beetles per plant threshold at the green bud stage, and he had opted to control the damage – the first time in four years that he has been forced to spray.
Ian Matts did highlight that as temperatures increased, he was finding Pollen Beetle at above threshold numbers in mid-April, but opted not to spray as he felt the crop would soon be in flower and the risk of damage would pass.
Chris Baylis also added that he chose not to spray in order to retain beneficial predators in the crop, and to make use of Pollen Beetle as pollinators once the crop came into flower.
With the delayed growth of the crop this year, iOSR growers are already looking at how long they can keep plants working to build oil yield at the end of the season. James Chamberlain reported he will definitely aiming to leave the crop as long as possible prior to desiccation, whilst Chris Baylis highlighted that, after two years of farm trials, he is intending to leave the farm’s even crop to die off naturally before harvesting. He has previously seen useful oil yield increase in the final weeks as the plants die back, but is mindful of potential combining pressures; uneven crops will be desiccated as normal.
Following the iOSR discussions, and having seen experiences on a growers’ group trip to Germany, Chris Eglington opted not to desiccate any crops last year, but it was an experience that won’t be repeated again. “We will be desiccating for sure this season, but will work on crop growth and not date for spray timing, so will likely be later this year to give the crop more time,” he believed.