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Flowering N to feed OSR yields

Product Update
Amistar application in flowering OSR
Amistar in tank mix with foliar N at flowering OSR could help plants make best use of green leaf

This year’s relatively early and forward oilseed rape crops could be best placed to take advantage of late flowering N applications, according to Syngenta Technical Manager, James Southgate.

Longer post-flowering photosynthetic activity could help to drive yields and oil content as the pods fill, he told iOSR growers. The large green leaf area of vigorous crops would have already taken up a lot of the nutrients applied, so these crops may be best placed to utilise any extra N applied at mid to late flowering.

“Green leaf area is by far the most efficient at converting sunlight into yield, compared to pods or stems," he said.

“Crops that have retained healthy green leaf from Amistar at mid to late-flowering can retain significantly greater green leaf area through the post-flowering period to harvest,” advised James.

He pointed out that there is a strong indication that lack of sunshine in May and June last year – when radiation levels were 30% below the norm – was a primary cause of disappointing OSR yields. “There is no knowing that it will happen again this year, but it does reiterate the importance of maintaining green leaf area for as long as possible to utilise available light,” he said. “Those crops which held on later last year, even for a few days, reported to yield better.”  

James highlighted that the greatest benefit in retaining green leaf came from Amistar application at green-bud to early flowering, but there was still a significant effect with later applications from mid-flowering.

“Over recent years we have also seen Sclerotinia coming in towards the end of flowering.  The later application of Amistar has given good control of Sclerotinia and other late foliar diseases, such as Alternaria” he advocated.

“The key thing is that, even in the absence of disease, the yield increase from the green leaf retention always pays. However, it is important for growers to get the nutrition right so that the crop can reach its full potential,” James added.

Seasonal adjustment   

Northamptonshire grower, Ian Matts (below), has retained 40 to 50 kg N/ha of the crop’s allocation for a late flowering top-up. He highlighted that his second top-dressing applications were delayed this season and that crops had moved through growth stages very quickly, hence he cut back the overall rate at that time.

“We have made no change to normal N rate and timings - calculated after carrying out N mins and GAI assessments as crop came out of the winter,” he said, “Crops suffered minimal winter damage and GAI's of 1.6 to 2.3 was up on most years.” 

Application advice

Since the ADAS trials revealed no significant differences with timing around the flowering period - between the onset of flowering and two weeks after the end of flowering - Yara advocates the application can be tank mixed with a fungicide treatment where appropriate.

Syngenta Application Specialist, James Thomas (below), highlighted spraying advice for a tank-mix of Amistar with a foliar N feed should aim to achieve good coverage throughout the crop canopy, but retaining as much spray on the leaf surface and stems as possible.

“In tall oilseed rape crops boom height will have to be raised to maintain even pattern across the target zone, but operators should be aware of the risk of drift,” he warned. “If the crop is variable, they will need to adjust the boom height accordingly.” 

James also pointed out that foliar application of nitrogen can result in leaf scorch, particularly in hot or sunny weather, or crops under stress from drought.

“Since the key objective of both the Amistar and the nutrient application is to retain green leaf area, it makes sense to apply in the early morning when plants are least stressed, or the evening when it’s not sunny,” he advised.

For more information visit the FG Insight iOSR website:

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