A fresh look at cultivations’ role in tackling the blackgrass menace on heavy land unsuited to spring crops is under way in Cambridgeshire.

First year results suggest early direct drilling of winter wheat can be as profitable as other establishment methods on heavily-infested land, but – and it’s a big “but” – only if the essential herbicides work well.

Masstock Smart Farming’s trial, begun in autumn 2010, was triggered by many growers and agronomists while visiting the firm’s Stow Longa site in 2009-10, says the firm’s Steve Corbett.

Conflicting views on how the company should best approach blackgrass control highlighted how the impact of different cultivations had been forgotten, misinterpreted or simply ignored, he explains.

“The messages from previous work in this area are clearly still not getting through to everyone,” says Mr Corbett. “People aren’t thinking about them all the time as they should, so we felt the subject was well worth revisiting.

“It’s only when herbicides start losing control and blackgrass comes back to bite that many growers realise they ought to be thinking about cultivations as well.”

Working with machinery companies Lemken and Claydon, the firm set out to explore on-going levels of blackgrass control from several establishment methods (see box).

Sole crops for the five-year trial are winter wheat and winter rape, reflecting commercial practice on many farms with similar land, he explains. “Spring rape or spring cereals just aren’t realistic options. Winter beans are a possibility, but pure wheat/rape rotations are more popular.”

The 24m x 370m plots will be segmented and overlaid with relevant herbicide programmes over the next five years.

Min-tilling for the previous eight years on the chosen field had kept any weed seeds close to the soil surface. But the 295 blackgrass ears/sq m remaining at harvest after early direct drilling with no herbicide treatment displayed the severity of the control challenge.

“At the Stow Longa site we have consistently recorded 100 blackgrass ears/sq m, decreasing wheat yield by 1t/ha,” says Mr Corbett. The margin from early direct drilling without herbicide was drastically reduced.

The 2010/11 work confirmed, as expected, that ploughing, which he acknowledges can be expensive, and delayed drilling are the best ways to reduce such infestations.

The trials also found that early direct drilling plus a well-timed robust herbicide programme gave one of the highest gross margins. But the potential downside, if control fails, is heavy return of herbicide-resistant seeds, he explains. “Clearly living dangerously can pay off, but you need to get everything right.

“The field we chose has RRR resistance to several herbicides, including the fops and dims, flupyrsulfuron and Atlantis (iodosulfuron + mesosulfuron). Knowing the resistance status of your blackgrass is important because it allows you to choose the most cost-effective control approach. You don’t necessarily have to pursue the most costly route on every field.”

Trying to keep track of shed blackgrass seeds by checking germination in soil profile pits after rain is well worthwhile, he suggests. “Few remain viable after being buried below 75mm for more than four years.

“And because most of them at the start of the trial were confined to the top few centimetres, it gave us the chance to fully invert the soil by ploughing and effectively start afresh.

“But the ploughing must be done well, using skims as if you were working on grassland,” he stresses. “If you don’t get the surface layer into the bottom of the furrow you’ll end up, as with discing and tining, with seeds spread throughout the soil profile, creating a long-term control problem.”

Last season showed that shallow min-tilling ensured more blackgrass germinated before spraying off with glyphosate, a crucial treatment in dry seasons, says Mr Corbett.

The effects of last year’s cultivations continue to be seen in this season’s oilseed rape, he says. Half the area was established after ploughing and the other by direct drilling – both at right angles to the previous cultivations.

“Clearly what you don’t want to do is plough up buried seeds, though there could be scope for ploughing less deeply in the following season.”

Establishment techniques

• Direct drill (Claydon) on 25 Sept

• Direct drill (Claydon) on 12 Oct

• Compact-Solitair drill on 12 Oct following:-

• Ploughing to 20cm and pressing on 6 Sept

• Single pass to 20cm with disc/tine combination on 6 Sept

• Single pass with tines to 5-7cm on 1 Sept

• High speed “scratch” to 5-7cm for stale seed-bed on 1 Sept, followed by tined cultivator to 20cm on 21 Sept

Note: All Lemken machines except Claydon drill