Crop Watch: Why harvest 2016 yields varied widely

drilling winter wheat

© Tim Scrivener

Reviewing last season’s crop yields has identified several lessons, including the value of good headland management. Ryan Hudson saw up to 40% difference in yield between the headland and field middle.

In wheat, Neil Potts believes much of yield variation can be explained by perfect conditions for take-all.

In oilseed rape, Todd Hunnisett is not really seeing any cabbage stem flea beetle problems unlike David Martindale who has seen many, especially on the wolds.

And finally in Spud Watch, Andy Steven says the recent dry spell has hit tuber bulking, crating a challenge in getting tubers up to size.

East: Ryan Hudson

Farmacy (Hertfordshire/Bedfordshire)

Ryan HudsonWinter barley and oilseed rape yields were disappointing due to a combination of factors – mainly lack of radiation and flea beetle.

Wheat and spring crops, however, performed more in line with averages if not above which has been encouraging. Even spring crops on heavy land have done relatively well.

While reviewing yield maps, it is clear that one area pulling average yields down is the headlands, in some cases 40% lower than the middle of the field.

This difference is larger than other years, possibly a result of the wet autumn and spring last year and the constant turning on headlands.

See also: How to tackle take-all after disease enjoys perfect year

This has also led to discussions about better headland management and how to try and reduce the effect.

Very little rain throughout August and September has hampered oilseed rape establishment and where plants have emerged, flea beetle is causing problems.

Where crops have caught more rain, establishment is good despite the relentless battle with flea beetle.

A regular question has been when should we start drilling wheat? This will vary depending on farm and field. Dry conditions have resulted in very little weed germination, so consider how much blackgrass has germinated and been sprayed off relative to what we are expecting in the field.

Blackgrass has only started germinating over the last fortnight despite some seed-beds being sat for over a month. Once it reaches two leaves, it will be sprayed off and cultivated to get a further flush prior to drilling later in October.

I appreciate not everything can be left until mid-October so prioritising fields is crucial with cleaner ones drilled first.

Residual pre-emergence herbicides also require moisture to be effective, therefore, drilling now into relatively dry seed-beds will also result in poor herbicide performance.

North: David Martindale

AICC (Yorkshire)


The earliest oilseed rape crops are typically at the four- to five-leaf stage, while the latest sown crops are just beginning to emerge.

Flea beetle has been the hot topic in the past two weeks when unseasonably high temperatures allowed flea beetle to start attacking crops in earnest.

It has been a battle to control the flea beetles with insecticide efficacy reduced to all but a few days when the temperatures were so high.

Often repeat applications of insecticides have been required and in most cases, they seem to be doing just enough to allow the crop to grow away. 

Very cloddy seed-beds and wold land are the two main situations where flea beetles have been particularly troublesome.

Volunteer cereals, particularly barley, in oilseed rape have been quick to emerge and become quite thick in some crops. Applications of a graminicide have been applied to take out the early flush. 

Blackgrass has been quick to emerge and more than ever seems to show an innate ability to know when a crop has been drilled, as flushes of blackgrass in cereal seed-beds yet to be drilled have been disappointingly sparse.

Wheat and barley drilling has begun on fields with lower grassweed issues, but for those infested with blackgrass, it is a case of being bold and refraining from drilling.

This test of nerve has been severely challenged when the weather has been so good and neighbours are out sowing their crops. 

Where the temptation has been too great and cereals have been drilled early on blackgrass prone land it will be very difficult to achieve the desired level of control.

West: Neil Potts

Matford Arable (Devon)

Neil Potts

With little oilseed rape being grown and no cereals yet drilled here, there is little to report on the 2017 crop. So this is a good time to note a few of the lessons learned from the past season.

Yields have been extremely variable and this has been from field to field rather than from farm to farm. The question as always is why?

Winter barleys have ranged from quite acceptable down to utterly disastrous, the main reason being barley yellow dwarf virus.

Most of the region did not have a 24-hour period without rain between the 4 November and the end of February, which meant it was impossible to apply planned aphicide applications.

This, combined with a virtually frost-free winter, meant that aphid survival and activity was good.

Where Deter (clothianidin) seed treatments had been used as a seed treatment, this was not too disastrous. However, where Deter was not used and no aphidcide was applied, the ensuing infection was severe.

With all aphicides now having a statutory arthropod exclusion zone as part of their approval, the take-away lesson with winter barley is treat the seed.

Wheat yields have, however, been variable even in the absence of BYDV. The trend has been for the lighter and more drought prone or free-draining soils to yield better than the heavy land.

This is the complete opposite of what we would normally expect. Looking at why, again I believe the continually wet and very mild winter has played its part.

At harvest there were huge numbers of black roots, even in first wheats, although the crops had not shown the usual tell-tale white heads. Take-all favours mild wet conditions and last winter was perfect for the build-up of the disease.

Many of the heavier fields remained at carrying capacity until June, favouring further development of take-all.

As June was also wet the soil never dried up which allowed infested crops to remain green rather than exhibit the usual white head symptoms.

The result has been unexpectedly poor yields in some fields. I have had instances of wheat drilled on the same farm on the same day and managed identically ranging in yield from 5t/ha up to 10t/ha.

South: Todd Hunnisett

AICC (Sussex)


Within my patch we’ve just had the driest, cheapest and easiest cereal harvest for many years.

Yields have ranged from very poor to pretty ordinary, but quality has been good and the price is improving.

Many topics are under discussion – barley yellow dwarf virus, blackgrass and general grassweed control and aphid resistance.

My instinct is to advise people not to make knee-jerk reactions as a result of last harvest’s results, but we can always try and learn something.

I will certainly see more ploughing this autumn where possible, and where blackgrass seed return has been high as a result of poor control this spring, I shall be busting a gut to get at least two applications of residual chemistry applied this autumn.

Naturally this is alongside all the other common-sense advice of delaying drilling, stale seed-beds, pre-drilling glyphosate etc.

I am also acutely aware of the sense of nervousness that surrounds delaying drilling, when the last four winters have effectively had a travelling cut-off date from the middle of November onwards. One message is in difficult grassweed situations, if you can’t get it sprayed, then don’t get it drilled.

Winter oilseed rape has gone into generally good conditions, and the recent rain has been a godsend. Crops have come up well, albeit late, and once again we don’t seem to have had the flea-beetle problems seen elsewhere.

I can only put this down to the fact that in our area we have tended to grow rape in a maximum of one year in four, more normally one year in five or even six.

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