Seedbank studies illuminate weed management at Strategic Cereal Farm

To keep Italian rye-grass populations at manageable levels, Strategic Cereal Farm East is getting to grips with the weed seedbank. Henny Lowth explores how the results are shaping its integrated weed management plans.

The basics are often at the root of many problems. Weed management at Strategic Cereal Farm East is no exception.

However, a focus on the basics does not mean that complexity can be brushed aside. As most weed seeds reside at depth, the trick is to understand what lurks beneath the soil surface (and to never judge a book by its cover).

About Strategic Cereal Farm East

Strategic Cereal Farm East (Morley Farms) grows combinable crops and sugar beet on land owned by The Morley Agricultural Foundation (TMAF). It has hosted research trials since 1965 and prides itself on developing practical results for farmers.

When farm manager David Jones joined the AHDB Strategic Cereal Farm network in 2023, his first task was to identify the research questions to answer during the farm’s six-year tenure.

With a tight lid on the farm’s black-grass populations, Italian rye-grass has become the biggest headache. As both grass-weed species have developed resistance to some herbicides, it has added to the management challenge.

Recent evidence of glyphosate resistance in the UK Italian rye-grass population has only strengthened the importance of one of the farm’s research questions: is it possible to keep weed populations at manageable levels with less herbicide?

Seedbank investment

Sometimes, fields are classified as a ‘bad [insert weed name] field’ based on what is seen on the surface, which informs the management response.

However, emerged weeds potentially only represent 5–10% of the total population. They are just the tip of the iceberg. This is why the trials at Strategic Cereal Farm East are pulling apart the seedbank to determine the true extent of the challenge, provide clues about past management impacts and guide future action.

The researchers are examining several fields (with contrasting cultivation and cropping histories) associated with high levels of Italian rye-grass emergence.

In the first baselining year, the field earmarked for some mechanical weed control trials was scrutinised the closest.

Profiling weed pressures

Quadrats (square frames that define a specific area) are being used to help map the distribution of weeds on the surface.

To indicate the abundance, diversity and distribution of weed seeds in the seedbank, the researchers are analysing soil samples from three depths:

• 0 to 5 cm (most seedlings emerge from this zone)

• 5 to 10 cm (very few weeds emerge from this interface zone)

• 10 cm to cultivation depth (most weed seeds are in this zone)

Each soil sample was divided in half, with one-half placed in trays (a tray per sample). Every 30 days, emerged weeds were counted and removed, with the soil subsequently mixed. This continued for five months.

Originally, the experiment was in a polytunnel on the farm, but the management of irrigation and temperature was too challenging.

Using the other half of the samples, an identical trial was set up under controlled conditions in a glasshouse at NIAB Park Farm, which produced more consistent results.

On average, weed seedling density was around 18 plants/m2.

In contrast, the seedbank density (up to 20 cm depth) was as high as 119,000 seeds per m2.

The surface, which was dominated by Italian rye-grass, masked species diversity. The soil profile told a different story, with dozens of species present.

A new approach

John Cussans (ADAS), who helps manage the weed trials, says we need to rethink our relationship with weeds and nurture a ‘good’ seedbank.

In this context, there is no scientific definition of ‘good’, but it involves encouraging a seedbank with many species at similar levels, with seeds evenly distributed throughout the soil profile.

The trick is to avoid creating a niche that allows one species to dominate. As a rule of thumb, the more homogeneous the management, the stronger the niche produced.

For example, an available, affordable and effective herbicide can keep a weed in check. However, when that herbicide is lost, power can rapidly shift in a weed’s favour.

The organic sector already has a heterogenous mindset, and there are lessons that can be learned from it.

Although profiling a field’s seedbank yields useful data, the availability and management of protected structures (polytunnels and glasshouses) will cap interest in seedbank screens.

As a result, the research team is also investigating DIY approaches, including a basic ‘windowsill’ test, that can be easily adopted on the farm.

Even the creation of a mental map – based on field histories (cropping, cultivation and weed burdens) – could generate a useful profile of the seedbank.

As always, it is a trade-off between simplicity and accuracy.

Next steps

Historically, large quantities of weed seeds were ploughed in at the farm. As Italian rye-grass seeds remain viable for a relatively long time (over five years), this has contributed to the seedbank stocks, and the problem. Certainly, intensive cultivations could bring these seeds to the surface.

The weed seedbank studies have been expanded for harvest 2025, covering more fields. Soil lifted from the farm’s machinery is also being tested in trays to gauge the risk of spreading weed problems (within and across fields).

The first Strategic Cereal Farm East annual report (harvest 2024) provides further information on these tests, as well as trials on mechanical control methods (an inter-row hoe and a weed surfer).

Ultimately, David wants to quantify the benefits of controls, in isolation and in combination, to start developing guidance similar to that already available for black-grass.

The report also examines how environmental stewardship impacts weed pressures and two other trial topics: nitrogen use efficiency (NUE) and Barley yellow dwarf virus (BYDV) management in winter wheat.

David Jones said:″Grass-weed herbicides are under enormous pressure, which can lead to resistance and poor performance. Trials at Strategic Cereal Farm East explore the use of mechanical weed control, alongside herbicide control, to drive down the Italian rye-grass population in the weed seedbank.″

All three trial areas (weeds, NUE and BYDV) are being investigated for harvest 2025. As with commercial crops, the winter wheat trials are struggling through the cool and damp winter. Once again, the BYDV trials in the autumn were impacted by poor conditions. The good news is that the NUE trial plots have established well. The finer treatment plan details are currently being ironed out.