Blackgrass Battles

Today we are joined by Agrii's Jamie Lyttle, agronomist, and Greg Taylor, area business manager and agronomist.

Our focus is tackling a real challenge - blackgrass - and how, through identifying the problem, field-scale trials were able to find real solutions.

We hear from the agronomist on that farm about how possible solutions were identified to help manage this persistent problem. 

What is black-grass and why is it such a problem?

Black-grass (Alopecurus myosuroides) is a major weed affecting cereal crops across the UK. Its competitive nature means it can drastically reduce crop yields if not effectively controlled.

With each plant capable of producing thousands of seeds, infestations can quickly escalate if left unmanaged. Tackling black-grass requires a blend of cultural, chemical, and mechanical strategies – and that's exactly what these trials aimed to explore.

Where did the idea for the black-grass trial site come from?

It all started when Jamie Little noticed an alarming level of black-grass appearing in spring crops, particularly within the drill row spacings. This raised serious concerns about whether the current drilling technique was inadvertently encouraging black-grass germination.

Rather than just tweaking the approach, Jamie decided to think bigger, transforming a simple idea into a large-scale trial. What started with four drills in the first year expanded to eight drills, six cultivation techniques, three drilling timings, and three different seed rates the following year. The trial even included a chemical-free control strip to properly assess different management strategies.

Where is the trial site located?

The trial site is based just off the M40 near Brackley – a convenient spot just five minutes from the motorway, making it easily accessible for visiting farmers and agronomists.

Why do we need trial and demonstration sites like this?

Greg Taylor highlighted that agriculture is evolving rapidly, particularly with the rise in regenerative farming practices. As farmers aim to reduce tillage and input costs, making informed decisions becomes trickier.

Field trials like this one offer real-world insights, helping you see first-hand what cultivation techniques, drilling timings, and machinery setups deliver the best outcomes – and where certain approaches fall short.

What key questions should you be asking if you have black-grass on your farm?

Jamie pointed out that traditional advice around delaying drilling to tackle black-grass may no longer be practical. Wet autumns, like those recently experienced, have left late-drilled crops struggling.

Instead of relying solely on delayed drilling, it might be better to split your farm into thirds, adopt varied cultivation techniques, and aim for a mix of early and later drillings. This balanced approach could relieve pressure on your system while still keeping black-grass at bay.

What were the key lessons from last year’s trial?

One clear takeaway was the benefit of "pressing the reset button" by using a plough. Fields that were ploughed had significantly lower black-grass levels compared to those using minimum disturbance techniques.

Where early drilling took place after proper cultivation, crops were both cleaner and more robust. However, where direct drilling was used without prior cultivation, black-grass infestations could quickly get out of hand, especially in early-drilled plots.

Later drilling dates did help produce cleaner crops overall, but they also risked leaving crops weaker and more vulnerable during the winter months.

How effective was ploughing in controlling black-grass?

The numbers spoke volumes. In fields where the plough was used effectively, black-grass levels remained in the single figures per square metre. In contrast, where cultivation was minimal and no pre-drilling chemistry was applied, black-grass levels soared to over 100 plants per square metre – a serious threat to yield potential and long-term field health.

What broader trends emerged from last season’s trials?

Greg emphasised the importance of creating a "forced flush" of black-grass before drilling. By disturbing the soil lightly and encouraging a flush of weeds that could be sprayed off before sowing the crop, farmers were able to significantly reduce black-grass pressure.

Critically, this approach did not require investment in brand-new, expensive drills. In many cases, existing machinery could be adapted to support better cultural control.

How severe was the black-grass pressure at the trial site?

At the outset, the farm averaged around 650 black-grass plants per square metre. Cultivations such as using a TopDown tool helped flush up to 315 plants per square metre for pre-drilling control.

Where minimal disturbance tools were used, the figure dropped to around 114 plants, and where no cultivation was carried out, only 46 black-grass plants germinated – although this masked a bigger risk of later flushes once drilling disturbed the soil.

What changes has the farm made following these trials?

Following the success of the trials, the farm took decisive action by increasing its ploughed acreage from 100–200 acres to around 600 acres. This bold move to rotational ploughing has already delivered cleaner fields and healthier-looking crops, giving the farm a much stronger foundation for future seasons.

What are the next steps for the trial and the farm?

This year’s trial focuses not only on repeating last year’s success but also on assessing the impact of row spacings and chemistry choices. By monitoring untreated plots alongside treated ones, the farm hopes to build an even deeper understanding of how to manage black-grass effectively without solely relying on chemicals.

How integrated weed management (IWM) fits into the picture

If you're tackling black-grass, integrated weed management (IWM) offers a structured approach. It combines multiple strategies, such as delayed drilling, rotational ploughing, crop rotation, and use of competitive crop varieties.
This trial showed that blending cultural controls with timely chemical interventions can be far more effective than relying on one method alone.

Why should you visit a demonstration site like this?

Learning directly from real-world results can be invaluable. Seeing the differences between approaches - whether plough-based resets or minimum disturbance strategies - gives you practical insights that you can apply on your own farm.

And it's not just theory; it’s about margins too. Jamie shared that margins varied by nearly £900 per hectare between the best and worst performing approaches, underlining how critical good decision-making is for profitability.

If you’re serious about tackling black-grass and optimising your cropping strategy, attending a demo day could be an eye-opening opportunity.

How can you visit the site?

Agrii will be holding an open day at the Brackley site in June. By that time, the black-grass will be heading, providing a clear visual demonstration of successes and challenges across different treatments.
Invitations will be shared on social media, and all farmers are welcome to attend and speak with the agronomists involved.

You can also visit agrii.co.uk/events for updates and further information.

Glossary

Delayed drilling - Sowing crops later in the autumn to allow black-grass to germinate and be controlled before planting.

Pressing the reset button - Refers to ploughing the field to bury weed seeds and create a clean slate.

Forced flush - Light cultivation before drilling to encourage black-grass germination so it can be sprayed off pre-crop establishment.

Minimum disturbance - Techniques that aim to disturb as little soil as possible at drilling to limit bringing buried weed seeds to the surface.