Protect potential for oilseed rape oil bonus, growers urged

Protect potential for oilseed rape oil bonus, growers urged24 March 2023

UK oilseed rape (OSR) prices may have fallen from their approximate £600/t highs, but maximising oil content to optimise bonuses paid on top of yield is as important as ever.

That is the message from ProCam agronomist, Daniel Hatchett, who says if an oil bonus pays 1.5% of the crop’s purchase price for every 1% of oil content above 40%, there is a lot to play for.

“The key is to understand what influences oil production so agronomy can be geared accordingly,” says Daniel. “Oil content is affected by plant density, the number of pods per plant and the number of seeds per pod. For maximum oil content, photosynthesis must be maximised. Maintaining the correct amount of green area in the crop is therefore key.”

Nitrogen (N) is a prime driver of photosynthetic activity and yield, says Daniel, however, applying excessive N to push yield can adversely affect oil content, while severe sulphur (S) deficiencies can also impact on both seed and oil yield. 

“For a tonne of seed yield, 15kg/ha of S is suggested to be needed. If S is deficient, as well as having yield implications, the chlorophyll content of seeds is raised and they turn green. This reduces quality for crushers and potentially oil content,” he explains.

“As well as macronutrients, micronutrients must also be in balance. Manganese deficiency alone can drastically decrease the crop’s ability to photosynthesise, even without visible symptoms. But an important period for influencing crop green area is around flowering,” he says.

“We know the disease sclerotinia can have a significant impact on yield, and controlling it with a robust fungicide at the correct flowering stage is critical. By utilising an SDHI and/or strobilurin for this, there’s an additional greening benefit which is extremely useful in building yield – even in the absence of disease.”

In addition, Daniel says maximising light penetration throughout the crop is hugely important for photosynthetic activity, so checking the crop’s green area index and selecting a fungicide with PGR activity is critical where canopies are overly thick. 

“The canopy can be optimised further by applying a biostimulant treatment containing nutrients and pidolic acid at yellow bud stage. This is because pidolic acid enables the crop to use N more effectively, helping to promote green leaf retention and chlorophyll content, both of which are crucial during pod-fill. Indeed, late N in OSR has been found to push yields and oil content. So a pidolic acid-containing treatment also fits well ahead of a later foliar N spray applied at mid-flowering.”

At the end of the season, Daniel says it is crucial to get harvest management right. “Seed filling in OSR occurs over roughly six weeks, with most oil being laid down during the second half of this. Desiccating or swathing too early risks losing up to 2% a day in yield and compromising oil content. Alternatively, harvesting too late risks seed losses due to pod shatter. So it’s about finding a balance.

“Applying a well-timed pod sealant against shatter and choosing the optimum time to harvest can substantially raise oil yield. It may be tempting to tank-mix a pod sealant and desiccant, however their optimum timings often don’t coincide. Last season’s high oil contents could potentially be attributed to pod sealants being applied separately from desiccation due to the crop’s high value. This year should be no different. Doing everything to preserve yield and promote oil content is likely to give the best financial reward.”