Cereals LIVE 2020 - Grass weeds

Successful grassweed management relies on developing a strategic approach that combines a long-term view and proactive tactical control. Syngenta grass weed research at the Barton Black-grass Innovation Centre and Doncaster Ryegrass Innovation Centre is combining innovative and practical integrated control solutions to manage grass weed populations at economically and agronomically sustainable levels – and it is working. Use this page to explore how you could incorporate various techniques into your on-farm strategies.

A total approach to grass weed control

An integrated approach to grass weed control is critical, taking into consideration cultural control options, herbicide strategy and application technique.

Key learns from Barton Black-grass Innovation Centre

The key insights from Barton come from overlaying weed control tactics over multiple years, and monitoring both weed control and margins. The site is now in its fourth year and we have begun to establish some interesting principles.


Seed dormancy is the term used to describe when a grass weed seed will not germinate even when all of the necessary conditions for germination are met. 

Weather conditions during maturation influence the dormancy of black-grass: a hot, dry year results in low dormancy in freshly shed seed, whereas a cool, wet year triggers a higher level of dormancy.

At Barton, dormancy tests have shown high dormancy in all seasons except 2018/19, following the hot summer of 2018.

Watch the video and listen to our dormancy soundbite to find out more about grass weed seed dormancy. 

Know what you're up against

1. Population2. Resistance3. Dormancy

Dormancy animation

At Barton, in our matrix field, we have crossed both cultivation technique and crop species to look at the effect of population, resistance and dormancy across the rotation. The work spans 5 years to enable effects of the rotation to become evident, for both grass weed control but also margin over input costs across the rotation.

Use our Cultivation Insight Tool to visualise the effect of different combinations of cultivations on black-grass distribution in the soil. 

Cultivation matrix findings

Our findings over the last three years suggest that using the same cultivation year on year isn’t the way to achieve the best margin or black-grass control. We found:Best margin: DD/Min-till/DDBest control: DD/Plough/DDWorst margin: Plough/DD/DDWorst control: Continuous min-till

Black-grass control

This table shows the effect of each cultivation on black-grass control in each season.


This table shows the effect of each cultivation on margin in each season.

The impact of seasonal context

As you can see the cultivation strategy that has given the best ‘control’ (or reduction) in black-grass over the 3 year period is DD/Plough/DD. This is despite the Plough giving the best control on average in both years one and two when considered as individual seasons. Best control was seen in a situation where the previous year’s plough offered a ‘re-set’ before direct drilling, meaning there was only one season’s seed return to contend with. Due to the low dormancy of that freshly shed seed residual herbicides worked well where that seed was on the surface in the direct drilling. The position of the plough in the multi-year strategy is something we are interested to understand further as the project progresses.

The best margin came from a DD/Min-till/DD strategy where there was a balance of moisture retention in undisturbed soils in dry summers and good establishment in the wet autumn of 2017.


At Barton, in our matrix field, we have crossed both cultivation technique and crop species to look at the effect of population, resistance and dormancy across the rotation. The work spans 5 years to enable effects of the rotation to become evident, for both grass weed control but also margin over input costs across the rotation.

Black-grass herbicide strategy

Cultivation method, drill date and soil type all have an impact on when black-grass seeds will germinate. This has implications for your stacking versus sequencing approach and timing of herbicide application.

Where black-grass emerges from affects herbicide performance

Our data shows that where black-grass emerges from (due to cultivation) affects herbicide performance. In autumn 2018, leaving seed on or very close to the surface helped with pre-em control. In this low dormancy year, black-grass seed germinated quickly and the large stack was the best option in a direct drilled situation. Where weeds emerged from deeper, they emerged over time and the sequence showed an advantage over the large stack.However, in the high dormancy year of 2016, seed on the surface germinated over a longer period of time, and there was an advantage to sequencing herbicides, even in the direct drill situation.

A spring crop needs to be competitive for good black-grass management

In the crop rotation matrix poor establishment of spring barley due to the dry 2019 spring gave poor yield, return and the worst black-grass levels.If you don’t establish a competitive spring crop, you’re possibly losing all you have gained in the extra stale seed bed by allowing too much black-grass to thrive in the crop and return more seed.


1. Map where you predict grass weed seeds are based on previous cultivation strategies.

2. Monitor weather at weed flowering to help understand dormancy for the coming season.

3. Adapt your herbicide strategy accordingly, using stacks or sequences for best control.

4. As a guide, aim to apply pre-em within 48 hours of drilling; apply sequences 3 weeks later. Adequate soil moisture is important for good performance of residual chemistry.

5. Start spring cropping in the autumn by preparing seed beds to achieve good crop establishment.

More about Barton

Find out more from Barton Black-grass Innovation Centre

Key learns from Doncaster Ryegrass Innovation Centre

The ryegrass Innovation Centre at Doncaster is part of a network of trial sites across the country, providing practical solutions for farmers. The site is in its second year, and is starting to generate useful insights into the short- and long-term impact of cultural, chemical and application methods on grass weed control and yield.

Competitive crops can out-compete ryegrass

At Doncaster, we have found that greater competition gives fewer grassweed tillers. Hybrid barley is showing consistently higher levels of competition and a lower number of ryegrass tillers than winter wheat or conventional barley. Hybrid barley is also demonstrating a reduced number of weed ears, due to a greater proportion of weed ears remaining below the crop canopy.

Ryegrass herbicide strategy

Of all the potential active ingredients for pre-emergence control, DEFY® is showing that it is an essential pre-emergence herbicide partner product for both winter and spring cereal crops. Regardless of the weather extremes seen over the last 2 autumn seasons, increasing rates of Defy increases control. We saw that application timing didn’t have an effect on the high levels of efficacy achieved this season but with the unknown impact of seasonal variation our advice would always be to apply a pre-em herbicides on as early as possible.


DEFY contains prosulfocarb for the control of a range of broad leaved weeds and certain grasses in winter wheat, winter barley and potatoes.

Pre-emergence herbicide treatments create one of the biggest challenges for effective application. With no crop to intercept the spray, extra care must be taken to avoid drift, and to achieve even distribution of droplets on the soil surface to maximise efficacy. Trials at Barton and Doncaster last autumn have reconfirmed our previous findings around techniques to balance efficiency, efficacy and environmental impact.

90% drift reduction nozzles deliver more even distribution of spray droplets

Nozzle choice is a fundamental part of hitting the target and achieving effective coverage of the soil surface – to get the best control from all pre-emergence applications. Ensuring an even distribution of product over the soil surface will improve your chances of controlling the emerging grass and broadleaved weeds.Both good coverage and even distribution are necessary for maximum efficacy of your pre-emergence herbicide application. The graphics on the left hand side both illustrate 50% coverage. However, the drift prone nozzle is showing extremely uneven distribution of the coverage, so we would likely see uneven and poor levels of control.

200l/ha water volume provides more consistent results

Grass weeds are getting tougher to control. Trials over four years have demonstrated that 200 l/ha water volume provides more consistent levels of control, with an average of 10% higher efficacy compared with 100 l/ha.

Download the Spray Assist app

Syngenta Spray Assist is a new app created to help sprayer operators to select the most appropriate application techniques on-the-fly. The simple to use app links to live local weather data to analyse the factors that influence accurate application and potential risk of spray drift, including wind, rain or frost. The app suggests techniques to enable sprayer operators to mitigate risks or alter practices.


1. Consider crop competitiveness when choosing your crop.

2. Get your pre-emergence application on as quickly as possible.

3. Ensure 50cm boom height and maximum speed of 12km/h.

4. Adopt 90% drift reducing technology.

5. Map your fields with a traffic light system - most 'tough' sites will need 200l/ha water volume for best grass weed control. Where timing is under pressure, balance efficacy by using 100-150l/ha on lower pressure fields.

6. Download the Spray Assist app.

More about Doncaster

Find out more from Doncaster Ryegrass Innovation Centre