Living Mulches in Arable Systems - Mini Guide for UK Farms

What is a living mulch?

A living mulch typically consists of low-growing plants - often clovers or another legume - sown between or beneath main cash crops (e.g. cereal or OSR) to provide continuous soil cover. Unlike traditional cover crops, living mulches are maintained during the main crop’s growth cycle, delivering potential benefits such as weed suppression, carbon sequestration, nitrogen fixation, biodiversity enhancement and improved soil structure.

We settled on using small-leaved white clover (e.g. AberAce, Rivendell) in most projects for the following reasons:

• Low growth habit that creates relatively little crop competition

• Persistence of the white clover and its ability to tolerate herbicide applications, including glyphosate, at rates that are lethal to many common weeds

• Increasing biological diversity

• Nitrogen fixing ability

• Excellent root network

It is very important to use a small leaved variety, as these give the biological and rooting

benefits, with significantly less crop competition, resulting in higher yields from the cash crop. They have the disadvantage that the grazing / forage yield is significantly lower.

Why use living mulches?

• Suppress weeds naturally - by competing for light and space, living mulches can reduce the need for herbicides. There is significant evidence that they can reduce weed abundance and biomass, and therefore seed return (Costanzo & Bàrberi (2016), Gerhards (2018), and Schumacher & Gerhards (2022))

• Fix atmospheric nitrogen - white clover can fix 150 kg N/ha, although the amounts will vary significantly, improving fertility while potentially cutting input costs

• Improve soil biology - living roots stimulate microbial activity, enhance mycorrhizal associations and build organic matter, improving water-holding capacity

• Protect soil year-round - mulches can reduce erosion, run-off, leaching and compaction risks

• Forage - living mulches can potentially be grazed within the arable rotation. Small-leaved clover varieties (such as AberAce) are suitable for grazing by sheep, although risk of bloat must be managed appropriately as with any rich swards.

Establishing clover living mulch in OSR: a case study

Oakbank first trialled clover as a living mulch in oilseed rape (OSR) in 2017, using the Sky Easy Drill at the Sky Agriculture trial site. We mixed 3kg/ha of AberAce white clover with OSR seed and drilled both together. The great advantage of this method is

that it allowed the clover to be established without any great effect on the OSR crop, apart from the choice of herbicide and that does need to be carefully considered on a field-by-field basis.

Clover for blackgrass control on heavy land

In partnership with Indigro, we have also explored using clover living mulch in cereal rotations on heavy soils, where blackgrass is a persistent problem. After a particularly wet winter and spring in 2020 delayed spring cereal sowing, we broadcast 15kg/ha of the small-leaved white clover variety ‘Rivendell’ following light cultivation and then rolled it in. The result: a uniform, successful establishment of the clover.

Sheep grazed the clover in late summer, delivering excellent forage. We then removed them to allow weeds to emerge before applying 1.5l/ha glyphosate. This suppressed the clover briefly, but also released nitrogen, giving the following winter wheat crop a natural nutrient boost.

Winter wheat was drilled into the clover carpet using a disc drill, to protect the stoloniferous clover and avoid encouraging too much weed germination.

Are there drawbacks?

Yes - without proper management or in particularly dry seasons, competition with the cash crop is likely to occur. Innovative Farmers field lab trials saw yield reductions of 30%, and Carof et al (2007) article on "Undersowing wheat with different living mulches in a no-till system - yield analysis" found a living mulch could significantly decrease wheat yields (19-81%), linked in their case to biomass of living mulches and weeds at the time of flowering decreasing grain numbers. Any reduction should be considered within the context of cost savings, which can be significant depending on your system.

Getting the seed rates of both the cash crop and the living mulch well balanced at the establishment phase is critical. If the mulch is drilled too thick it will inhibit the yield of the cash crop but too thin and it won’t do as good a job as a mulch. It is important also to appreciate that our intention is to keep the mulch alive for 5+ seasons, so the benefits will accrue over that time and perhaps beyond.

Beyond clover mulches: alternatives worth considering?

While small-leaved white clovers are now the most common living mulch species in UK trials, and remain the most compatible, other options may suit certain systems better:

Species	Benefits	Considerations
Lucerne (Alfalfa)	Deep-rooted, drought-tolerant, high N-fixer. Ideal for dry or lighter soils where persistence is key. Supports soil structure and fixes significant nitrogen over time.	Requires well-drained, alkaline soils (pH 6.2+). Not shade-tolerant and less suitable as an undersown mulch in dense cereals. Can dominate if not managed.
Birdsfoot Trefoil	Low-growing, "bloat-free" forage legume. Compatible with low-input systems. May persist well in marginal land.	Slower to establish than clover. Needs careful establishment and is sensitive to competition.
Subterranean Clover	Self-regenerating annual; good early ground cover. Suited to drier, lighter soils and often used in southern Europe.	Less winter-hardy and not ideal for heavy UK soils. Performs best in systems with fallow or break periods.

👉 If you would like to find out more about establishing or managing a living mulch as part of your rotation, our team is happy to help guide you. Call us on 01480 890686 or email info@oakbankgc.co.uk

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Frequently Asked Questions (FAQs)

Q: What crops can I under-sow with a living mulch?

A: Most cereals, maize, and some legumes are compatible. Wider rows or strip-till setups help reduce competition.

Q: Does a living mulch reduce crop yield?

A: It can. Significant yield penalties have been recorded, particularly in the first year. However, improved soil health and reduced input costs can offset this over time.

Q: When is the best time to sow a living mulch?

A: There is no single best time to establish a living mulch, as each option has trade-offs:

• Summer (post-early cereal harvest) - allows mulch to grow from autumn into winter, but dry soils may hinder germination.

• Spring with spring-sown crops - dry weather gives the mulch a competitive head start, but cold early temperatures may slow growth.

• Late summer/autumn - better moisture may aid establishment, but wet soils can limit machinery access, and growing time is short before winter sets in.

• Undersowing winter cereals in the Spring - offers good mulch growth during the weed-sensitive period, though vigorous crop can suppress mulch in conventional systems.

Establishment can be challenging and context-dependent.

Q: How long will a living mulch last?

A: With correct management, clover-based mulches can persist for 2–3 years or more. Plan an exit strategy to prevent dominance in future rotations.

Q: Is a living mulch the same as a cover crop?

A: No, a cover crop is usually terminated before the cash crop is sown. A living mulch grows at the same time as the main crop and stays in place throughout the season.

Q: Can I use living mulches in organic systems?

A: Yes, they are especially well-suited to low-input or organic rotations, reducing dependency on herbicides and synthetic fertilisers.