As featured in Arable Farming Magazine

Getting oilseed rape back on track

by Arable Farming Magazine April issue

With oilseed rape yields slipping, a Thames Valley farming business has implemented a cabbage stem flea beetle (CSFB) management plan in a bid to renew confidence in the crop.

Oilseed rape growing has been pulled back from the brink at Manor Farm, Drayton St Leonard, near Wallingford, in the past two seasons.

With a determined effort that has also led George Farrant and his Agrii agronomist, Ollie Fairweather, to virtually halve their annual nitrogen use, standing them in particularly good stead with current fertiliser prices.

Seeing yields down to less than two tonnes per hectare, S.J.Farrant and Son was not the only Oxfordshire grower despairing of oilseed rape in 2019.

But the family’s 150-200ha annual crop is now firmly back on track despite continuing to be grown one year in three on drought-prone Thames Valley gravels.

Mr Farrant, who runs the family’s 800ha farm, plus a further 330ha on contract, says: “We didn’t see much in the way of problems immediately after the neonic ban.

“In fact, we averaged almost 4t/ ha at Manor Farm in 2015, which is very good for the ground.

After this, though, our yields slipped steadily to 3t/ha or less.

Then, in 2019, we brought in just 1.8t/ha.

“There seemed to be more beetles every year and our long-standing late August min-till and drill regime just couldn’t cope with the extra pressure – even with five or more insecticide sprays.

We didn’t know what to do.

Disastrous “First wheats have always done reasonably well here at around 9t/ha but second wheats are disastrous.

This means we follow our wheat with winter barley, which often averages nearly 10t/ ha and gives us the perfect entry for our key cereal break – winter OSR.

As our land is poorly suited to beans and presents a huge risk for most spring crops, the future looked pretty bleak if we couldn’t make the oilseed rape work.

“Something clearly had to change, but no-one seemed to have any idea what.

Until we came across Agrii’s CSFB management plan at an OSR day at AgriiFocus near Marlborough, that is.

Two years on and I’m glad to say yields are back to their long-term average of just under 3.5t/ha with margins again rivalling first wheat.”

The OSR turnaround at Manor Farm has involved de-risking the crop with key elements of the eight-point plan, but by no means all.

Very limited break crop options, for instance, mean the rotation has not been significantly extended, although a small acreage of peas has been added to the mix.

Nor are companion crops being grown as they have been found to take more away from the crop in moisture on the light land than they contribute to CSFB protection.

Equally, the practicalities of combining brackled barley rules out leaving long straw, as does a straw-for-muck swap with a neighbouring beef farm.

Instead, the focus has been on single pass sowing into undisturbed barley stubble to minimise the ‘green on brown’ attractiveness of the crop and critical seedbed moisture loss.

At the same time, sowing has been brought forward by around two to three weeks.

Varieties showing the greatest autumn and spring vigour in Agrii trials have been prioritised and a phosphite and pyrogltamic acid biostimulant seed treatment has been introduced as standard along with a specialist starter fertiliser.

Soil nitrogen supply Particular attention is also now given to getting the crop away rapidly and reliably in spring, with top dressing to carefully measured green area index (GAI) and soil nitrogen supply from as early in the season as possible.

Balanced trace element nutrition based on autumn, early spring and stem extension tissue testing further ensures the greatest nutrient use efficiency and timely autumn and spring plant growth regulation gives the most efficient canopies.

Mr Fairweather says: “When I started working with George in 2019 our first priority was the establishment regime.

Top-down cultivation and drilling was giving away too much moisture and leaving the bare soil contrast that attracts CSFB to the emerging crop.

This meant the beetles were eating the OSR faster than it could grow away from them.

“We needed to redress this balance and open up topsoils prone to slumping, all without spending on new kit.

Our solution was to equip Micro Wing legs on the existing Cousins V-Form subsoiler plus Opico seeder – that had been found wanting for OSR sowing in the past.

“This did mean spending £5,000 up front.

But the investment has proved well worthwhile.

The ultra-low disturbance legs are doing a good soil lifting job while conserving moisture and avoiding the sort of slot that leads to uneven sowing.

Rolling immediately afterwards at a steady pace then ensures decent seed-to-soil contact.

“On this land, the OSR invariably runs out of moisture and has a major pause in growth at some stage in autumn,” says Mr Fairweather.

“Our aim has been to make sure this doesn’t happen before the 4 leaf stage, after which it can tolerate a surprising amount.

“We do this by sowing as soon in August as we can to be sure of enough moisture with a system that preserves as much of it as possible.

We treat all the seed with Take-Off to boost rooting and put it into stubbles that have had a dressing of Agrii-Start NP+ OSR, providing 30kg/ha of nitrogen, protected phosphate and extra boron around 10 days beforehand.”

All-round vigour in the varieties grown is equally important in the Manor Farm recipe, although variety choice remains confined to Clearfield hybrids, following serious erucic acid penalties suffered in 2017.

Moving on from DK Imperial CL and DK Impressario CL, the InV1266CL in the ground this season went into the winter even better grown than last year’s crop.

The 2021 crop had early February GAIs of around 1.75.

With N-Min testing showing a soil contribution of 91kg/ha, this gave a total nitrogen supply of 179kg/ ha.

In theory then, only an extra 40kg/ha would have been needed for the farm average 3.5t/ha.

Moving to this from the standard 200kg/ha of the past would have been a step too far, though.

So, 100kg/ha was applied for the 4.5t/ha potential the crop clearly had – and would certainly have delivered had it not been for very small seed resulting from the dry summer.

“This saved us a good 80kg/ ha,” adds Mr Fairweather.

“Alongside our key need to make sure the crop gets through what we see as the most critical period of the whole year – December to March – this is another good reason for getting the best-grown OSR before Christmas.

Larvae “Whatever we do, we know we’ll have flea beetle larvae these days.

And sowing earlier means we are likely to have more of them.

For the least risk we simply have to have a crop able to power away from any setbacks in spring.

If it’s too small, too weedy, lacks early get-up-and-go, or sits too wet or cold, it can very rapidly go backwards, leaving us looking at serious losses and limited options for replacement in spring.

“We don’t use any pre-ems and the only costs we incur other than the seed before our early October cut-off for deciding whether or not to keep crops are the starter fertiliser, a graminicide for the barley volunteers and, maybe, a small amount of insecticide.

A decent establishment risk share scheme covers us for much of this investment if establishment goes wrong and we have a well-subsoiled field we can put into something else.

“Our level of risk escalates massively, though, as soon as we start putting on any Clearfield herbicides, Centurion Max [clethodim] or Kerb [propyzamide] – not to mention fungicides, PGRs and spring fertilisers.

“Knowing we have a sufficiently good crop with the enough spring vigour gives us the confidence to invest in these crucial inputs once we get past the ‘point of no return’.

“We are happy to use a good PGR in autumn as well as spring to manage our canopies – and doing this with Architect [pyraclostrobin + prohexadione-calcium + mepiquat-chloride] which combines growth regulation with good foliar disease activity this season makes things even more flexible.

Although it’s all prescriptive, following tissue testing, we don’t stint on micro-nutrition either – primarily manganese, magnesium and boron here.”

So what are the Manor Farm team’s plans, now they have successfully got their OSR back on track? Mr Farrant and Mr Fairweather are looking at a number of tweaks to their current regime.

First and foremost is questioning whether to continue with Clearfield OSR on land that has more than its fair share of broad-leaved weed problems but few issues with charlock, runch or hedge mustard.

Mr Farrant says: “If, as we suspect, erucic acid contamination problems are behind us now, ordinary OSR would give us a much wider range of higher yielding, high vigour hybrids to choose from.

“There’s no escaping the fact Clearfield herbicides can be quite hot on the crop, either.

Equally, we could make some good cost savings by not using them.

“We’ll definitely be building up our experience with and confidence in basing nitrogen applications on GAIs and N-mins,” he adds.

Support “Foliar N is something we are also keen to explore to support our crops later on and in dry conditions.

And if we replace our Horsch Pronto with an Avatar, this could give us some useful extra establishment options too.

“All in all, we are very relieved to again be looking ahead at our OSR with optimism.

The past two seasons have rebuilt our confidence in a crop that is so essential to our rotation.

On our ground a consistent 3.5t/ha would give us the sustainability we need.

Especially if we can further reduce our growing risks and costs.”

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2022-06-08T16:07:15+01:00June 8th, 2022|Blog Post|
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