‘Stick to plan’ to beat blackgrass

Early-sown winter wheat is yielding well and profitable once again on heavy land at Agrovista’s flagship trials site in Northamptonshire – despite a huge background blackgrass population.

“Historically, if wheats weren’t drilled by mid October you risked not getting them in at all,” says Agrovista consultant and Lamport AgX trials co-ordinator Niall Atkinson.  “But going earlier was asking for trouble.”

The Lamport AgX trials site has solved this conundrum, says Mr Atkinson – by using sequences of autumn cover crops and spring break crops to reduce blackgrass pressure, minimising soil movement and improving soil health.

This strategy – supported by an appropriate herbicide programme — has proved itself over several very different seasons. “After a run of autumn cover crop/spring breaks, we are now successfully alternating winter wheat with a cover/spring break.”

In 2023, first winter wheats averaged just under 10.5t/ha following a range of crops, with some plots exceeding 12t/ha, with almost no blackgrass – a big improvement from a decade ago when blackgrass populations exceeded 2000 plants/m2.

“You need to choose your fields carefully and stick to the guidelines or risk going backwards. You also need to be reactive – if something goes wrong and blackgrass starts taking hold, you may need to delay your first wheat and grow a further cover crop/spring crop break.”

Farming systems

Much of the work carried out at Lamport can attract valuable Sustainable Farming Incentive payments. But whole field SFI actions are proving difficult to integrate into rotations at Lamport due to the enormous blackgrass challenge.

Over-winter cover crops, the mainstay of operations to control blackgrass and improve soil health, are currently worth £129/ha, but that’s just the start. Several other options that now attract payments under the scheme are under scrutiny.

Winter bird food (AHL2) and legume fallow (CNUM3), look tempting on paper, paying £853 and £593/ha/year respectively. But both plots, which were drilled in April, have been destroyed. 

Hamish Wardrop, Agrovista’s rural consultancy national manager, said: “The winter bird food established OK but there was a mass of grass weeds as well, and the pressure was too high to continue with it on this site.

“The legume fallow also established reasonably well, but it suffered badly with slugs, flea beetle and weevil. And we also have grassweed pressure.

“These actions can be a good choice in some situations, but you have to go in with your eyes open. We can’t lose sight of what we are trying to achieve in bringing back first wheats into the rotation.”

Low input cereals

A low-input cereal action (AHW10) aims to create an open-structured cereal crop that encourages wildflower species to grow within it, providing habitat and summer foraging for birds, pollinators and other wildlife.

It pays £354/ha/year, and a further £129/ha is available for a preceding over-winter cover crop. Normal fertiliser, fungicide and growth regulator inputs and rates are permitted – but herbicides are restricted.

“You have to sow the cash crop at a reduced seed rate – we chose spring oats and went at two-thirds rate, or 270 seeds/sq m,” explains AgroVista technical manager Mark Hemmant.

“We have to select carefully where to grow it on at Lamport, but we have achieved the aims; while is a little bit of blackgrass coming through, if you are well on top of grassweeds and have a good rotation, it could be useful.”

Spring wheat and beans

The benefits of adding beans to a spring wheat crop at 10 seeds/sq m are also being assessed. That would attract a £55/ha companion crop payment under SFI for a seed cost of about £15/ha, and could help mitigate take-all.

“The net benefit of what you spend on bean seed compared what you get back looks good, provided there are no adverse effects on blackgrass control or yield,” says Mr Hemmant.

The beans were destroyed around flag leaf timing as some inputs are not approved for that crop, but the crops appear to have thrived. 

“Black oats in the cover crop aren’t enough to prevent take-all in a wheat-dominated rotation in an autumn like 2023. But if we introduce wheat plus beans in the spring, might the undoubted soil benefits that beans bring change things?”