Return to pro table winter wheat production despite high black-grass burden

Now in its eighth year, Agrovista’s Lamport AgX flagship trials site has evolved into one of the country’s leading workshops for sustainable agriculture.

The Northamptonshire site, previously known as Project Lamport, is examining how rotations, cover cropping and regenerative agriculture principles can interact to improve soil health and yields while maintaining black-grass levels at manageable levels.

It is a tough testing ground, situated on heavy, high calcium soils that are difficult to manage, with a background black-grass population of 2,000 plants/m2.

Over the years, Agrovista has refined an autumn cover crop/spring cereal rotation to keep black-grass under control.

A cover crop, based on black oats, is established in early autumn after a light cultivation to maximise black-grass establishment, before bulking up to condition and drain heavy soils over winter to enable spring drilling.

The cover crop and ‘trapped’ black-grass are sprayed off ahead of the spring cereal, which is direct-drilled to minimise soil disturbance and black-grass emergence.

“The aim is to get lots of black-grass to “The aim is to get lots of black-grass to germinate in the autumn, and none in the germinate in the autumn, and none in the spring,” says technical manager Mark Hemmant “Everything else bolts on around this.”

While spring cereals have been the cash crop of choice so far, recent work has shown that a return to winter work has shown that a return to winter wheat is feasible, but perhaps only one wheat is feasible, but perhaps only one year in three on sites where the resistant year in three on sites where the resistant black-grass seed burden remains very high, even after eight years of cultural and chemical controls.

Legume fallow – AB15

One option to help farmers return to winter wheat uses a legume fallow, based on the Countryside Stewardship AB15 option.

The official option was tweaked because it became swamped with blackgrass after being drilled in August, as per the guidelines, and it became puddled in the winter.

Niall Atkinson consultant and trials coordinator at Lamport AgX, comments: “It has done nothing to date for black-grass control or soil health, and environmentally the mowing stipulated in the scheme has been a bit of a disaster.”

In the alternative option, a black oat and phacelia cover crop was established in August 2018 to trap black-grass and condition the soil. It was desiccated the following January and again just before the AB15 legume mix was established in the spring.

“The mix grew away very well and we didn’t need to carry out successive mowing to control blackgrass. We sprayed it o in August 2020 and in October established winter wheat with a direct drill to minimise black-grass germination,” says Mr Atkinson. “You can see the odd black-grass plant but control is very acceptable – the wheat looks like a 10–12t/ha crop.” The winter wheat will be followed by a return to the cover crop/spring crop sequence for at least two years. “A second winter wheat might appear tempting, especially at current wheat prices,” says Mr Hemmant. “But black-grass explodes. Even after seven years of very low seed return, we still haven’t depleted the weed seed bank sufficiently to be able to rely on chemistry.”

The modi ed AB15 is not allowed under midtier rules, being spring drilled, but could be under the Sustainable Farming Incentive. But, if the legume mix still has to be grown for two calendar years, it would have to be followed with a spring crop rather than winter wheat.

because it became swamped with blackgrass after being drilled in August, as per the guidelines, and it became puddled in health, and environmentally the mowing drill to minimise black-grass germination,” says Mr Atkinson. plant but control is very acceptable by a return to the cover crop/spring crop sequence for at least two years. “A second winter wheat might appear

Winter wheat – Lamport system

A further method tested under extreme conditions could enable growers to return to winter wheat without sacrificing one or two years of cash cropping.

This trial follows a third winter wheat crop that failed in summer 2019 after being overwhelmed by black-grass, despite a £150/ha herbicide spend.

Half the plot was earmarked for ploughing and half for a cover crop/spring crop sequence. However, heavy autumn rains put paid to ploughing plans, thoughts of a cash crop were abandoned and a cover crop was established the following summer.

In the other half, the cover crop was drilled on 5th September 2019, trapping black-grass and conditioning the soil. It was desiccated in early January and spring oats were direct-drilled on 27th March 2020 and went on to yield just under 8t/ha.

“We then direct-drilled winter wheat in midOctober when conditions were on the limit,” says Mr Atkinson. “Despite that, two years after a Mr Atkinson. “Despite that, two years after a disaster, the wheat looks almost as good disaster, the wheat looks almost as good as that following our modi ed AB15. as that following our modi ed AB15. “And we’ve also had an 8t crop of spring oats in the meantime and have ended up with very little black-grass. “Conventional wisdom says we should have pressed the reset button should have pressed the reset button and ploughed, but this alternative and ploughed, but this alternative appears to work well.” appears to work well.”

Regenerative principles on test

A further study at Lamport is assessing the prospects of reducing reliance on conventional agrochemicals. A plot of spring wheat was sown in late March, along with sweet allyssum to encourage beneficials and berseem clover to condition soil and x nitrogen.

“We’ve basically taken away conventional chemical inputs,” says Mr Hemmant. “We’ve used no fungicide seed treatments, no herbicides and minimal foliar fungicide.”

The plot received 20kg/ha of controlled-release foliar N, replacing 100kg/ha of conventional N to reduce free nitrogen in the soil and to lower the carbon footprint.

A comprehensive biostimulants programme was adopted, including Tiros seed treatment to x N and, with seedbed-applied Phosphorus Liberator, to release soil phosphate. Amino acid products Kloro ll and T6P were applied at conventional fungicide timings, along with L-CBF Boost, a food source for soil microbes and fungi.

“This approach seems to have worked well,” says Mr Hemmant. “It’s a really interesting concept. If we can adopt areas of regenerative farming within a conventional system to make it more sustainable, that has to be good.” FG