Arable News

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Tillage options must suit your grass weed control

A robust herbicide sequence only carries you so far in the fight against grass weeds, so cultivation methods still remain a pivotal part of any control programme. Here we get the opinion of three farmers adopting different tillage systems to combat their particular weed burden.

The rising cost of production and increasingly adverse weather pushed Shropshire farmer Tim Ashton to give no-till farming a go on his 300ha of cereals and pulses. Three years on and the impact that the new system has had on the weed burden has been surprisingly beneficial.

“Sterile brome under our non-inversion minimum tillage system was becoming an increasing problem. Since transitioning to no-till, it has practically walked off the farm,” he explains.

By easing their crop rotation and leaving weed seeds on the surface to chit, Mr Ashton says they now have a much better understanding of the brome’s biological profile as well as observing huge savings in fuel, machinery and crop chemistry costs.

“Leaving weed seeds on the surface as we do means they are left to rot or be eaten by birds. One of our most valuable pieces of kit is a set of rolls. We go over with these to ‘wake up’ surviving seeds and encourage them to chit before drilling. Then you can just go over with some glyphosate before your crops come through,” he says.

“We’ve found we need less crop protection chemistry in no-till fields because you are not establishing weed seeds inconsistently by chitting them throughout the season.

“No-till has certainly helped with our weed control and soil health,” he adds.

Black-grass burden

For black-grass burdened Chris Byass, who grows 110ha of wheat, barley, oilseed rape, vining peas and borage near Driffield, Yorkshire, his no-till system has improved soil health and biodiversity no end, but weed control is variable.

“No-till farming hasn’t made a lot of difference for us in black-grass control. When we were ploughing six years ago black-grass wasn’t an issue, but because we share a combine with a neighbour the seeds have moved. Now we are fairly on top of grass weeds, but we have two fields with major problems, so it is by no means cured. I don’t feel like ploughing would be the answer to black-grass control because we need to keep the seed on the soil surface.”

Chris uses a Horsch CO4 drill with narrow JJ Metcalfe tines to go through chopped straw without pushing it into the ground, as well as a Moore drill for peas and direct drilling into cover crops.

Cover crops play an important role on the farm, retaining nutrients and improving soil structure. “I don’t like to see bare soil so if there is any chance to get a cover crop in I will. This year I am trying something different – I have just bought a harrow which I’m going to pass through the stubble, followed by a roller to get a chit from black-grass seed before drilling. Late drilling in no-till isn’t really an option here so I encourage chitting and then spray. We then follow up with Liberator (flufenacet + diflufenican) on autumn cereals and Atlantis/Pacifica (mesosulfuron + iodosulfuron) as required in the spring.”

Rotational ploughing

Rotational ploughing has long been recommended as one of the key building blocks for long-term black-grass control and, with methodical ploughing, one farmer has seen black-grass numbers go from being critically high to barely in existence.

Matthew Denby who works 720ha of heavy clay and medium marshland on the family farm in Lincolnshire trialled a number of different methods to tackle black-grass on his farm, but each time the problem seemed to worsen resulting in yield losses.

“We now use a plough for cereals two in every three years for black-grass and a Simba SL with low disturbance legs for drilling oilseed rape, which has been very valuable as a cleaning crop.”

The level of black-grass on the farm has fallen so much that this season Mr Denby was able to simply hand rogue any stray weeds, alongside a robust pre- and post-em herbicide programme.

“Ploughing in late July to early August after rape means we can create a really good seedbed ready for the autumn. This allows time to create a stale seedbed for delayed autumn drilling in dirtier land, which can be treated with glyphosate. Soil is also more likely to be moist during this time which sees better efficacy from the residual herbicides.”

With heavy soils and limited options, other black-grass control methods aren’t always possible, but ploughing to get the best establishment followed by a cleaning crop of rape keeps the seedbank at depth where it remains manageable, he suggests.

“Late drilling on a min-till system poses too much risk for us and spring crops are too unreliable leading to wet soils. For us, the best black-grass control, most profitable farming and wheat yields still come from ploughing.”

Less favourable

Harper Adams visiting Professor in Agricultural Engineering, Professor Dick Godwin, says that improving soil drainage would go a long way towards helping to reduce black-grass, but if growers are turning to conventional ploughs to bury weed seeds, there are crucial elements that must be considered to prevent seeds re-emerging next season: “Conventional ploughing can still have a place in some weed control rotations if there are weed seeds on the surface that can’t be got rid of any other way,” says Professor Godwin.

“There is evidence that ploughing deeply and pushing the seeds to a good depth will bury them, but you mustn’t then plough deeper the next year because it will bring all the seeds back up to the surface. Make sure you bury deep and then work with shallower cultivations or no-till in the successive years.

“You must also set the skimmer on the mouldboard plough to make sure the entire trash residue and seeds go into the bottom of the plough furrow. Skimmer setting is critical if you’re going down the plough route,” he warns.

  • Written by: Farmers Guide
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