Spring barley is one of the best crops for tackling even the worst herbicide-resistant black-grass, but crop agronomy must be tailored to weed control from the outset, leading agronomy firm Hutchinsons says.

Up to 98% black-grass control was achieved from growing spring barley in one commercial field at the firm’s black-grass centre of excellence near Brampton, Cambridgeshire, last season and technical manager Dick Neale believes the crop can make a real difference to weed burden if managed correctly.

“Any spring crop gives you the option for extra stale seedbed control in the autumn and allows black-grass to germinate over the winter, but spring barley has the added advantage of being highly competitive and will have a massive competitive effect on spring-germinating black-grass.”

But any grower opting for spring cropping primarily to control black-grass must do all they can to get the best results, even if that means compromising on yield, he says. “It’s worth taking a bit of short-term pain for the long-term benefits of reducing black-grass populations.

“Spring barley is traditionally a light land crop, so growing it on heavier, moisture-retentive soils where black-grass is more of an issue, means there has to be a change in agronomy if we’re to optimise weed control and deliver a commercial crop.”

Minimise cultivations

Restricting soil disturbance to the top 50mm (2”) is key to controlling black-grass in any situation and spring barley is no exception, says Mr Neale.

“Some people prefer to plough heavy land and leave it exposed to frosts over winter, but that can create significant challenges when trying to get on in the spring to create a seedbed. Minimum tillage does give a better chance of establishing a seedbed, but it is still not an ideal solution.”

Mr Neale says the Cousins Surface cultivator, which has been designed for black-grass control, offers an effective answer across most soil types. The tines work at a consistent shallow depth of 50mm, which retains organic matter near the surface, encourages weed seeds to germinate in the top layer of soil and leaves seeds at lower levels undisturbed.

He acknowledges water can appear slower to infiltrate immediately after heavy rain, but insists that preserving the natural structure aids drainage throughout the profile and allows soils to “carry” machines more easily than after ploughing or discing.

Delay drilling

If weather and soil conditions allow, Mr Neale says it can be useful to establish a flush of black-grass that is sprayed off prior to drilling barley in the spring.

A single shallow pass with a stubble rake in early to mid-March will stimulate black-grass germination, and can be done quickly with a relatively light tractor, he notes.

“If you do opt to do this though, you have to allow at least a month to ensure everything has germinated before spraying off with glyphosate. Drill too soon and you could end up with a lot of black-grass emerging within the crop that has effectively been given a head start.”

It may be more practical to go straight in with the drill as the first cultivation in the spring. “At least the black-grass and barley will start growing at the same time and the crop should be able to outcompete it.”

Drilling should still be delayed until April, he advises, as the warmer soil and air temperatures will favour more rapid establishment and growth. “If you’re on heavier land, droughting-out later in the spring is likely to be less of an issue.”

Seed rates should be kept high where weed control is the priority, although Mr Neale says exact rates will vary depending on seedbed conditions and timing. As a rough guide, he recommends rates of around 400seeds/m2 for mid-April sown crops, while earlier sowings (mid-March) may be nearer 325 seeds/m2.

There are a number of pre-emergence herbicide options available in spring barley but Mr Neale says flufenacet should form the backbone of any programme. “If you can present the chemistry with a low, stifled black-grass population, it’s possible to get very good levels of control.”

Manage lodging

Lodging is one of the biggest challenges when growing spring barley for weed suppression and Mr Neale says extra care must be taken to manage this risk from the start.

That means careful analysis of background soil fertility prior to any nitrogen applications and adopting a robust growth regulation strategy where needed.

“Spring barley grown on light, sandy soil wouldn’t normally require a high PGR input. But if you’re growing it on heavier moisture retentive land then don’t be frightened to commit to decent growth regulators, such as products based on trinexapac-ethyl or prohexadione calcium + mepiquat chloride at earlier growth stages with ethephon applied around flag leaf emergence.”

“It’s all about developing a tailored agronomy package that delivers both weed control and a commercial crop from land that may not traditionally have been suited to growing spring barley.”