Black-grass economics: every percent of control counts

John recently joined a BASF roundtable with Andersons’ senior analyst, James Webster-Rusk, BASF business development manager, Stuart Kevis and Lincolnshire grower, Pat Thornton to discuss the true cost of black-grass and how to optimise control.

“In drier conditions the potential to lose black-grass seeds from the soil surface through predation and natural losses far outweighs the value of cultivation to promote germination.

“Despite the challenging reality of farming today – the financial pressure, the extreme weather, the geopolitical landscape - the fundamentals of weed management haven’t changed,” says John.

It’s an important point for Stuart who emphasised applying residuals like Luximo® at pre-emergence of the target weed remains crucial, as does, applying the best chemistry first.

“That means, using Luximo within the base pre-emergence programme,” he says.

The value of herbicides

BASF has modelled the effects of various treatments and programmes, evaluating the cost of the herbicide spend and the yield lost over a first and second wheat.

“Assuming that there are 5 black-grass plants/m2, flufenacet + diflufenican + aclonifen, is likely to offer 73% control. That means 27% of the black-grass is not controlled. If the crop is expected to yield 9t/ha, at £170/t that will cost, in total, £284.30t/ha and 73% of that is lost yield. There’s also the high seed return to consider. 7,371 seeds will be added to the seed bank,” he explains.

Stuart compares this pre-em treatment with bixlozone + beflubutamid + pendimethalin which offers less control at 65% and consequently incurs a higher cost of £478.49 over the two years. Of that, 70% is due to yield loss.

“With 12,075 seeds returned, this treatment will incur costs for years to come through increased herbicide spend, yield loss and may demand cropping changes,” he says.

In contrast, Luxinum® Plus + Stomp® Aqua + diflufenican offers 86% control.

“As a stand-alone treatment, this still isn’t enough to keep populations at a standstill and needs to be supported, but it is the most cost-effective solution of the three,” says Stuart.

“With just 14% of the black-grass plants not controlled, its cumulative cost is £205.06/ha. This is largely due to the preserved yield. It is a more efficient base pre-emergence application.”

Through the model, Stuart shows that achieving high percentage control is the most cost-effective way of managing black-grass, even in low pressure scenarios.

John agrees, noting: “Markets are quite unpredictable and therefore it is important not to make short term decisions that have long term implications.”

On-farm economics this autumn

With farm consultancy, The Andersons Centre, anticipating another difficult year for farm finances, James says there’s a real need to focus on getting the most out of every pound spent.

“Margin-wise, 2026/2027 doesn’t look any better than this year.”

The combination of uncertainty around subsidies, elevated fertiliser and red diesel costs, together with extreme weather conditions are all taking their toll.

“Everything we do must give a return on investment,” agrees Pat, who farms 140ha in Lincolnshire.

“You often see differing advice for high, medium and low grassweed pressure scenarios but why would you risk it?” he asks. “I wouldn’t scale my herbicide programme back, it is contributing to the bottom line.”

Despite having managed high black-grass pressure down to more manageable levels, Pat says that black-grass continues to drive major business decisions including the rotation, drilling dates and sowing rates.

“I wouldn’t fool myself into thinking that the problem has gone away, but it has certainly reduced.”

Looking ahead and with wheat harvest underway, Pat is resisting the temptation to drill.

“It is important to stick to those fundamentals. Although I would hate to miss the opportunity to get crops established, in the back of my mind I know I can’t let my drilling date creep forward too much.”

“I’m looking for that extra 1% in everything that I do and in terms of grassweed management, that means delaying drilling and using the best chemistry that I can.

“The maths is clear,” he says.

Growers wanting to explore the true cost of black-grass can get access to the model via BASF’s Grassweed Cost Calculator here.