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Counting the cost of black-grass

Do you know how much black-grass is costing your business? One agronomist has done a detailed analysis for a typical heavy land farm. Teresa Rush reports.

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Counting the cost of black-grass #arable #farmprofitability

Take one eastern counties heavy land farm. It has historic black-grass issues; confirmed resistance to ALS group herbicides (mostly EMR); failing control from post-emergence herbicide chemistry and ‘average’ field drainage. Last season black-grass control on this farm cost on average over £50/hectares more than it did a decade ago.

The man crunching the numbers is Strutt and Parker agronomist Jock Willmott, who was using actual figures from a Bedfordshire farm managed by the business to highlight the cost of black-grass to agronomists and scientists at the British Crop Production Council’s annual weed review meeting.

According to Mr Willmott, there are several factors contributing to the rising black-grass cost burden and significant among them is the decline in efficacy of post-emergence herbicides.




The farm’s Gatekeeper figures show a total expenditure of £65/ha on grass-weed control in 2006/2007.

Mr Willmott says: “You can see Atlantis working. It takes the pressure off what we do in the oilseed rape, where control is fairly straightforward.”

Good control of black-grass in wheat also helped to keep down grass-weed control costs in oilseed rape crops – total spend in oilseed rape during the same season was £72/ha. But since then costs have climbed steadily; so what is going on?

“Where we are finding the pinch in terms of increasing costs is in residual black-grass materials. Chemistry has got more expensive and in addition we are finding we are having to use so much more of it.


See also: Weed screen explores options for grass-weed control


Herbicide programme autumn 2015

Winter wheat





Pre-drilling glyphosate x1




Pre-emergence - 3 litres/ha Crystal + 2 litres/ha trifluralin




Post-emergence 0.4kg/ha Atlantis +1 Bio power




Total spend on grass-weed control in wheat




Oilseed rape

Centium 0.25 litres/ha




Trifuralin 2 litres/ha




Falcon 0.5 litres/ha




Kerb Flo 2 litres/ha




Total spend on grass-weed control in oilseed rape




Source: J.Willmott, Strutt and Parker




Herbicide programme autumn 2016

Winter wheat





Pre-drilling glyphosate x3




Pre-emergence stack (Avadex, Crystal, DFF, liberator




Early post-em (pre-leaf 2 of early grass)




Total spend on grass-weed control in wheat




Oilseed rape

Glyphosate x 1




500g/ha metazachlor




120g/ha clethodium




Late autumn full rate propyzamide + carbetamide




Total spend on grass-weed control in oilseed rape




Source: J.Willmott, Strutt and Parker





“Where we were using a light pre-emergence and a follow-up post-emergence, we are now into this situation of stacking residual chemistry. This, as we all know, isn’t sustainable,” says Mr Willmott.

“The staggering thing is how much the cost has increased, partly because of [price] inflation of the actives, partly because we are having to use so much more.”

For this Bedfordshire arable business black-grass control costs have increased from £65/ha to £134/ha in wheat and £72/ha to £103/ha in rape – increases of £69/ha and £31/ha across the two crops, with most of the extra cost incurred in the wheat crop.

The total cost across wheat and oilseed rape amounts to an extra £34,200 a year on the crop protection bill and furthermore there is now less wheat and oilseed rape in the rotation (the 2015 combined wheat/OSR area was 85% of the 2007 area).

“As a result of not really being able to control the grass, we have to grow less wheat and that acreage has been taken up with spring barley and spring beans,” Mr Willmott adds.

And this forced shift in cropping has also contributed to increased costs.

“Wheat is important, wheat is the cornerstone, it is the most profitable crop, it always has been,” he says. But the winter wheat acreage harvested in 2016 will be down 10% on harvest 2007. [See graph].

“With the inclusion of spring barley and spring beans, the earning potential of the rotation has come off by £30,000,” he adds.

But that is not the end of it. Drilling wheat three weeks later is reducing the output potential of crops. Spring barley and spring beans are lower output potential crops. Some 23ha of land worse-affected by black-grass have been taken out of combinable crops and put into grass, or let.

Savings in input costs on spring crops deliver some cash flow advantage, Mr Willmott acknowledges. “But you ask any farmer, he’d rather have the income potential on the top line, push it hard and make costs fit underneath it.

“We would like to grow lots of wheat, we have been there before but at the moment we absolutely can’t, we have no choice. We can’t have uncontrolled black-grass.”

And still there is more to consider.

“So we’ve changed the rotation, we have got extra crops; we are being forced to drill into a narrower window and we have pushed that window closer to Christmas, when it gets wetter.

“Since Atlantis control dropped off there has been more [black-grass] seed return, more glyphosate use, much more spraying and because we are drilling later, the crops are harvested later. We need to do all that over a shorter period, so we need more resource to do it.”



Black-grass control - associated costs


Increase in farm cost


£100,000 in extra depreciation cost




One more staff member at 75% of time


Additional herbicide cost


Total extra cost to farm of black-grass control

£72,000 (6% increase in overall farm costs)

Plus extra seed to compensate for later drilling, more competition


Source: J.Willmott, Strutt and Parker



Extra resources

Extra resources

The extra resources required have included a larger sprayer and combine, additional labour and greater quantities of herbicide. Yet despite this extra investment and the rotational changes, the black-grass battle is by no means won, believes Mr Willmott.

“I am concerned the spring cropping we are putting in will change the population dynamics of what [black-grass] we have got. We are seeing quite big flushes in spring crops where we haven’t had them before.

“Maybe it’s because we’ve such a big burden of black-grass and a proportion of that happens to germinate in spring but it does seem we are getting more grass in spring crops than we used to have and our only real push-back against that is higher seed rates.

“Pre-emergence spring residuals are notoriously variable but on the plus side we can push these [spring] crops hard and get some tremendous yields.”

With black-grass costing the farm £72,000 a year, he is calling on scientists and weed control experts to help deliver new approaches to black-grass control. These might include, perhaps, very local information on black-grass seed dormancy which could help inform cultural control decisions, or novel control methods.

“The decision to go drilling in autumn is the big decision and is a very much a roll of the dice. We need some sort of localised information to help, in terms of black-grass, with its dormancy. If we get it wrong it contaminates the crop and the rotation.


See also: Using rotations to control resistant black-grass

“Chemicals are cyclic, we know that. We are coming to the end of Atlantis and perhaps to the end of some of the residuals we use across the rotation. Novel control methods are required – can we make use of natural predation [of seed]? Are there ways of affecting black-grass dormancy or seed set perhaps?

In some fields only a break from cropping will get the farm ahead, concludes Mr Willmott.



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