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Optimising OSR establishment to reduce crop risk – Arable Farming – David Howard, Dick Neale

Following challenging autumn drilling conditions and pillaging by CSFB over the last couple of years, many growers will be questioning the value of including winter oilseed rape in their rotation...

Oilseed rape has reached crisis point, with decisions being made now on individual farms as to whether to continue with the crop albeit on a reduced area, or to remove it from the rotation altogether.

Sustainability of the crop is a very real issue and without a doubt it is essential that when gross margins are prepared that they make allowances for the huge variability in the crop’s performance, acknowledges David Howard, Hutchinsons head of integrated crop management.

“When committing to growing OSR it is essential to recognise the potential risk, as a large percentage of the crop’s total spend takes place in the autumn before the crop’s viability can be determined,” he says.

He believes business attitude to risk is one of the biggest determining factors as to what extent OSR will continue in the rotation, adding the increased management and time of the individual grower will dictate this.

David Howard, Head of integrated crop management

How to make the right decision?

In light of this risk management approach how can growers make the right decisions about growing the crop this autumn?

Hutchinsons technical manager Dick Neale believes this is a decision that can be made at the time of drilling depending on soil conditions.

While no-one can question the havoc that cabbage stem flea beetle (CSFB) has brought to crop emergence over the last two seasons, Mr Neale believes this has been vastly exacerbated by the very dry conditions the crop has been drilled into, hampering its ability to get up and away.

“Seed was planted into dry and dusty seed beds, germination and subsequent crop emergence was therefore slow and erratic, depending on where seminal roots found moisture as the crop germinated.

“The resulting staggered emergence was like a picnic for the pest as it picked plants off as they emerged.

“However, if this autumn is different, and soils at drilling are moist, the seed can imbibe all that moisture and emerge evenly, thereby diluting the beetle pressure and the crop will have a much better chance of getting up and away.

“If seedbeds are dry and dusty, do not waste time and resource sowing OSR, but if conditions are favourable then it is definitely worth a shot.”

Dick Neale, Technical manager

It is all about being flexible, he says. “For example, say on August 10 we have had plenty of rain and there is sufficient moisture in the soil, then it is worth looking at drilling rape. However, if over the next five days, conditions are hot, dry and windy and the soils are drying rapidly then stop drilling. If it rains again then pick up the drilling again, but if it stays dry then call it  day.”

Cultivations

Cultivations play a key role in maintaining moisture, says Mr Neale.

“Once the seed has started germinating it cannot be allowed to dry out in the following seven days; if the seed dries out four days later it will not establish – the soil needs to be able to provide that moisture.

“A minimally tilled, fine seedbed with good seed to soil contact is needed for the optimum soil moisture retention. This means not turning over the soils more than 2-3cm on the surface.”

He also suggests rolling a couple of times; the first time to maximise the seed to soil contact and the second time to firm the ground so CSFB cannot get into it easily.

Seed rates

Mr Neale does not believe there is a need to increase seed rates.

He says: “Keep it at 75-100 seeds/sq.m. Increase the rate and it gets chomped and you have wasted money, or if the crop does not get away you end up with too many plants and the subsequent management problems that go with that.”

He does recommend that the seed is dressed with Integral Pro (biological) or Accerelon (biological) seed treatments and/or Radiate (zinc).

“More recently precision drills have been useful in creating even, well established crops. This is because each seed is planted exactly the same distance apart at exactly the same soil depth. Do not go out to buy one, but if already in the shed or a contractor can access one, then it is worth it.”

However, it is worth noting that the soils need to be in the best conditions for this approach to work to its full potential, he says.

Protection

Maintaining long stubble on the field is an area Mr Neale believes brings some protection against CSFB for the newly emerged plant.

“By allowing field spiders to build webs just above ground level, this offers maximum potential for beetle entrapment.

“Soil coverage with residue, biosolids, FYM or digestate also maintains soil moisture and disrupts targeting of small plants by the CSFB by smell.”

Mr Neale underlines the importance of preparing the seedbed to be pre-loaded with nutrient N, pointing out that the newly emerged crop must suffer no delay in the availability of nutrients.

“N already in the soil has been observed to be more effective than freshly applied or after drilling.”

It is certainly worth considering a late N application to wheat or barley crops earmarked for OSR drillings, he says.

“50kg straight granular AN shortly after ear emergence to pre-load soil with available N, provided N max is not exceeded for the current crop, is a good strategy.

“We also know that phosphate vastly improves the speed and vigour of establishment.

“I would also suggest using a placement fertiliser – in fact, in my opinion, it is a no brainer. But it is important to get this right to ensure that the nutrients are applied where needed and also in the right amounts,” he adds.

Formulated

“It is best to use a product formulated for this approach and machinery adapted to place it so it sits down and around the seed; in our trials, over several years, we have had excellent results with Primary-P which is formulated for placement, applied directly around the seed.

“Primary-P provides a very concentrated, available but persistent form of nutrients, which is why rates are lower.

“However, if not using Primary-P, it is still possible to use standard products, but think about how much you are using and how it is being applied to the seedbed. For example if using DAP as a placement option, reduce how much you are applying. You do not need the same amounts as when broadcasting it on, as the fertiliser becomes concentrated.

“Liquids work well as a starter fertiliser for OSR. Direct the spray to one side of the row or temper the amount of fertiliser that’s put down directly with the seed.”

Approaches to reducing CSFB damage in the 2021 crop

Consider late N applications to current wheat and barley crops in fields earmarked for OSR drillings this autumn. 50kg straight granular ammonium nitrate shortly after ear emergence to pre-load soil with available N, provided N max is not exceeded for current crops

Ensure adequate moisture in seedbed during drilling for rapid germination and growth

Place P or N+P with the drill

Maintain residue cover or compost and cut stubble higher to allow spiders’ webs to be suspended above ground

Choose varieties with good autumn vigour

Dress seed with Integral Pro or Acceleron seed treatments and/or Radiate

Seed rate should not exceed 100 seeds/sq.m

Focus on seed placement depth, aim for optimum evenness of emergence

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