Plough and pre-ems kick blackgrass into touch

After more than a decade, Lincolnshire grower Daniel King is finally beating blackgrass with a mixture of later drilling dates and cultural control – rather than a sole reliance on agrichemicals.

For the past 10 years, Mr King says he has tried virtually every product and every cultural technique to rid his blackgrass from Pasture Hill Farm, near Bourne. In his opinion, the only solution left for growers is to plough only when conditions are perfect or use minimum tillage techniques plus robust pre-emergence herbicide mixtures that use all available chemical options and modes of action.

“The plough is the last resort, so it’s always going to be a grower’s ace card,” says Mr King. “Don’t use it unless the conditions are perfect, because there is nowhere else to go if it goes wrong. I hate ploughing, because it’s slow and expensive and up until two year’s ago, we hadn’t ploughed on this farm for 15 years.”

Ploughing was reintroduced in 2013 because of blackgrass getting out of control in some fields, adds Mr King. Where it was used correctly, he achieved 95% control. But last year – where it was used in the wrong situation – he only achieved 50% control of blackgrass.

Mr King has used cultural techniques to good effect to keep on top of blackgrass recently. But he acknowledges that some tricky autumns have seen the problem start to return.

“In 2012, we ploughed everything after oilseed rape because a lot of viable blackgrass seed was returned to the soil after harvest, so I knew I had a huge seed burden,” he says. “We ploughed slow and deep to bury the seed. It was proper inversion that put seed right at the bottom – nine inches deep. The cereal crop that was then drilled and emerged into virtually clean fields.”

In 2013, Mr King drilled his oilseed rape with a Cousins subsoiler with micro wings attached, which minimised soil disturbance and has left fields virtually free of blackgrass. The oilseed rape herbicides Kerb and Crawler have worked well to eradicate blackgrass in most situations.

On the flip side, he says that some of the later-drilled oilseed rape land in 2013 was ploughed but because the soil was not in the right state and patchy blackgrass has emerged.

“It was mostly too dry to start with and so crop emergence was patchy,” he says. “Not much blackgrass has come back, but there is enough to be a problem cultural techniques alone cannot sort out.

“My advice to growers with blackgrass is that if the conditions aren’t conducive to ploughing, then leave it in the shed, rather than use up your ace card.”

Mr King uses the rotation based on barley, wheat, oilseed rape and spring barley to aid cultural control. Fields earmarked for a spring crop are cultivated with a TopDown and sprayed up to three times with glyphosate prior to drilling with a 4m Vaderstad Rapid.

For winter crops, wheat varieties with vigorous growth habit such as Edgar and Santiago are selected because they compete with blackgrass. Seed rates can be up as high as 500 seeds/sq m.

Mr King delays drilling for as long as possible in the autumn and last year he started in mid October and finished in mid November.

“That’s late for around here; drills are normally back in the shed by the end of October unless there are roots in the rotation,” he says. “Late drilling is very risky but where there is blackgrass about there is little option. Even though I had to go and buy a tined drill to cope with late drilling, and it might not be necessary to ever use it, I see it as an insurance policy against blackgrass.

“In the last three years we have nearly cleared up blackgrass on all bar one field which is on lighter land and had grown potatoes,” Mr King explains. “The field was ploughed, ridged up, bedtillered and planted so the full nine inches of topsoil had been thoroughly mixed. Dirtiest field I’ve ever had, so we will think very hard about whether or not to rent out our land for potatoes next year.”

Mr King says that he tailors his pre-emergence blackgrass control to the type of resistance he knows exists on the farm. After a decade of manufacturer run trials he knows exactly what herbicide is likely to work in which field.

“This year I aim to use Avadex as a pre-emergence in the autumn and three days later follow up with combinations of Crystal, DFF, Defy and FPU,” he says. “FPU works particularly well on the heavier soils and Defy seems to work well on the lighter land.”

Last year on his worst blackgrass fields he applied a four-way mix of Crystal at 4 litres/ha plus 0.2 litres/ha of DFF plus 2 litres/ha of Defy and 20g/ha of FPU. It was not possible to use Avadex because the land was too wet to travel at the time.

He adds that later drilling helps with control because the moisture is essential to get the best out of the 
herbicides.