Arable News

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Re-think brings black-grass hope for Suffolk grower

Volunteering to be part of a programme to radically re-think the farm’s approach to black-grass control was a bold step for one Suffolk grower, who now eagerly awaits yield and weed control results this harvest. Dominic Kilburn writes.

You can’t blame Andrew Colchester for being a little cynical of change. A third generation tenant farmer, he’d been brought up on the family’s 75ha farm in north Suffolk where a plough-based system to establish all crops had been in operation for two generations before him – first his grandfather and then his father. So it made perfect sense for him to continue the tradition at Church Farm, Thrandeston, particularly with winter wheat averaging 10.5t/ha in recent years.

But as has been the case with many farms featuring heavy land and operating under a typical arable rotation, the onset of black-grass and the difficulty in controlling it prompted Mr Colchester to think again.

Weed campaign

In Autumn 2017 as part of the ‘Arable Weed Control’ campaign, BASF launched a series of on farm trials. Farmers were invited to tell the company about their biggest weed control challenge and then, with an independent team of experts, including ADAS weed specialist Dr Sarah Cook, the company put together a programme of advice which aimed to cover all areas of agronomic practise to see if, collectively, weed control problems could be solved. 

According to BASF’s campaign manager for cereal herbicides, Ruth Stanley, some of this advice was a complete shift away from current farming practise and which may have put a few potential trialists off, but one of those brave enough to take up the challenge was Mr Colchester, one of only two farmers who decided to take the trial forward.

Church Farm can be divided in two by soil type; the “top half” – a medium sandy loam, suited in particular to growing potatoes, and the “bottom half” – a heavy clay more suited to wheat and oilseed rape, said Mr Colchester, who co-hosted an event with BASF on his farm in early May.

The rotation on the farm has included OSR; winter wheat; winter barley; potatoes; spring barley and, latterly, sugar beet. Due to slug issues and the problems and costs associated with metaldehyde pellets, the intention is to drop OSR completely while sugar beet was re-introduced into the rotation in recent years. “We’ve always believed in break crops and a variety of cropping has proved advantageous for the farm’s wildlife while spring crops offer us another opportunity to control black-grass,” said Mr Colchester.

All straw is removed prior to cultivations while imported muck is now being slowly introduced, and cover crops considered, for soil health and structural benefits.

Investment in land drainage and mole draining (on the heavy land) is also on-going.


All the farm is ploughed and pressed each year and cereals established using a power harrow/drill combination. “We let stubbles green up after harvest in time to hit one flush of black-grass ahead of the plough and power harrow/drill, and try to get everything drilled up before the end of September,” explained Mr Colchester.

“However, during the past 10 years, black-grass has developed into an issue on the heavy land. I became more and more aware of where it was and no chemical seemed to touch it, to the extent that we have even had hand-weeding in operation,” he said.

“We’ve tried a number of approaches in recent seasons in terms of chemistry applied as well as rotational ploughing, but the black-grass control didn’t get any better,” he added.

Together with BASF agronomy manager Hugo Pryce, who knew the farm well from agronomy work he’d undertaken in the past, and cultivations consultant Philip Wright, they discussed a plan to see what might work ahead of the 2017/18 season, hopeful that Mr Colchester would look at crop establishment differently to his usual practice. At the same time, a 7ha trial plot on an area of heavier, black-grass-infested land was earmarked on the farm.

Previous cropping on the chosen site included winter wheat in 2015, sugar beet in 2016 and spring barley in 2017 (the last time the ground had been ploughed).

According to Mr Colchester, the spring barley crop came off in wet soil conditions leaving 10–12cm deep wheelings, and compaction was discovered at a 20cm depth at various locations when test digs were made.

“It wasn’t the best start to the trial,” commented Mr Wright, “so we decided to go through with a 3m Sumo LDS 5-leg disc/tine cultivator first – in early September – which lifted and stretched the soil but didn’t bring anything to the surface,” he explained.

As part of the plan, the decision was made to delay drilling until mid-October, but as well as deciding not to use the plough for primary cultivation, the power harrow/drill combi was also dropped from the equation.

“In the end we got help from a local farmer and his Weaving GD 4.5m drill – a low-disturbance disc drill which literally lifts and then returns the surface during drilling,” added Mr Wright.

Winter wheat variety Shabras was drilled at 190kg/ha on the 16th October, 4–5 days after stubble had been sprayed with glyphosate.

“Delayed drilling is fine,” said Mr Colchester, who admits to feeling uneasy if cereals aren’t drilled up by the end of September, “but we are lucky in respect that we haven’t got a huge area to drill. However if you can’t get on at that time of the year, that’s when you start to have problems,” he stressed.

Rolls-Royce treatment

The decision was also made to go with a comprehensive herbicide treatment, noted Hugo Pryce, with the application of glyphosate pre-drilling followed by 15kg/ha Avadex (tri-allate) at pre-em, and 4-litres/ha Trooper (flufenacet + pendimethalin) + 0.2-litres/ha Hurricane (diflufenican) at peri-em. This compared with the farm’s standard treatment of 2-litres/ha Trooper + 0.3-litres/ha Herold (diflufenican + flufenacet).

“The application we went with was a Rolls-Royce treatment delivering 240g/ha flufenacet, 1,200g/ha pendimethalin + 100g/ha DFF,” he pointed out.

“This is a typical programme for many farms with similar levels of black-grass problems,” he added.

According to Mr Pryce, although black-grass on the farm hasn’t yet been tested, it’s likely that resistance, or partial resistance, is a factor. However, a combination of a moist autumn and the robust treatment delivered good black-grass control on the site to such an extent that a planned follow up with an application of flufenacet, later in the autumn, was deemed unnecessary.

Mr Colchester commented: “This herbicide programme cost a lot in my opinion – up to £80/ha – but if we get to harvest and it’s given us a crop, then it will have been worthwhile.

“What I was using as a standard treatment previously was probably half the price of this but it wasn’t doing the job,” he said.

Looking good

Fast forward to May 2018 and any uneasiness Mr Colchester was feeling last autumn as the crop went in the ground was starting to dissipate. Black-grass control in the autumn had been a success to the point that a contact herbicide follow up in the spring wasn’t required. “When I compared the trial with the rest of the farm in the early spring it looked a bit worrying, but the crop has now significantly improved and proof, of course, will be how many black-grass heads we find at harvest,” he commented.

“If I don’t see many black-grass heads in July and we get presentable yields, then I will agree that this system might just work for me.

“Late drilling, less tilling and a more robust chemical programme in the autumn has certainly made a difference and for us it’s probably easier to make a change like this with our relatively small acreage.

“It may be the case that we treat the two halves of the farm very differently in future; a focus on less tilling and more robust chemistry on the heavier, black-grass susceptible soils, but continue with our plough and power harrow/drill combi on the lighter soils where potatoes feature in the rotation,” concluded Mr Colchester.

How low should you go?

Wright Resolutions soil and cultivations consultant Philip Wright (pictured) says that he’s not ‘against’ the plough as there are times when it’s needed, but he reckons that every time it’s used then the ‘reset’ button in terms of soil structure has been pushed.

“In the case here at Church Farm, then Andrew Colchester has probably been ploughing too much – I would only plough one in every four or five years at the most,” commented Mr Wright. “If ploughing in black-grass seed it must be left down there for a number of years. It loses its vigour year-on-year but bring it back up to the surface soon after burial then its vigour will still be there,” he said.

“Low disturbance is part of the solution, but, for it to work, the depth of disturbance you give the soil when you drill, must be less than the soil surface cultivations carried out beforehand. So, for example, if a grower is focusing on a 60–70mm depth when planting a cover crop, then the depth of soil disturbance for the main crop drilled after should be no more than around 30–40mm.”


  • Written by: Farmers Guide
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