Multispecies or herbal leys – what are the advantages?
15 May 2025The use of multispecies or herbal leys has come more into focus over the last few years. These are swards with a mixture of grasses, herbs and legumes that confer many benefits. Although there have been concerns that there is some yield loss compared to a monocrop of ryegrass, the benefits of the different species in the multispecies leys should be considered.
Key Benefits
The benefits that have been outlined for multispecies swards are to the quality of the forage or grazing for the livestock, along with improving the soil health and carbon storage within the soil, as well as greater biodiversity. This relies on the differing rooting depths of the species that make up the sward mixtures and the species themselves.
A ryegrass sward has a mainly uniform, shallow rooting mass close to the surface of the soil and can be very reliant on the use of fertilisers to maintain growth and productivity, whereas different species within the multispecies sward have deeper rooting, allowing elements to be utilised deeper in the soil as well as the moisture at depth during drier conditions. This is without considering the advantage of including leguminous species that can ‘fix’ their own nitrogen (N).
Multispecies Swards In Practice
A set of experimental plots were established at SRUC Barony campus farm during April 2023 to investigate multispecies swards of increasing complexity compared to a fertilised (150kg N/ha equivalent) monocrop of perennial ryegrass (Pfert).
These mixtures were perennial ryegrass and red clover (PR), perennial ryegrass, red clover and tonic plantain (PRP), perennial ryegrass, red clover, tonic plantain and birdsfoot trefoil (PRPB), perennial ryegrass, red clover, tonic plantain, birdsfoot trefoil and burnet (PRPBB). It appeared that even after only one year there were advantages associated with the multispecies swards compared to the more conventional fertilised ryegrass.
The additions to the swards were selected for different criteria, such as the red clover for the production of N (between 150 – 200kg N/ha) and its deeper rooting system, in addition to the enhanced protein content. Tonic plantain (Plantago lanceolata) is a popular addition to sward mixtures in New Zealand for forage growth, deep roots, resilience and ability to use moisture at depth. It has also been suggested that plantain produces naturally a compound that inhibits nitrification in soil, leading to reduced production of nitrous oxide (N2O) – a greenhouse gas. Birdsfoot trefoil has been seen to increase milk and milk solid yields, reduce urine N and the condensed tannins it produces have been proven to result in a 13% reduction in livestock enteric methane emissions.
The results from the experimental plots were only followed over establishment in the early spring though to autumn the same year, with only two silage cuts being taken in August and October. Monitoring of the soil was done at the establishment of the plots and then again in October after the second cut. The yield results showed a significant improvement in total dry matter yield and less N2O produced for the multispecies mixtures compared to the fertilised perennial ryegrass, as shown in Table 1.
Table 1. Total Dry matter (t/ha) and nitrous oxide emissions (g N2O ha/day) from the different multispecies mixtures and fertilised perennial ryegrass.
| Mixture | Total dry matter yield (t/ha) | N2O produced (g N2O ha/day) |
|---|---|---|
| PRP | 9.19 | 9.62 |
| PRPB | 8.2 | 6.62 |
| PRPBB | 9.09 | 6.05 |
| Pfert | 5.39 | 27.53 |
Considering the soil health effects of the multispecies swards was interesting as the assessment of the soil structure using a visual survey method (https://www.sruc.ac.uk/media/xbrfn4x3/vess-colour-chart.pdf) showed an improvement for the multispecies swards i.e. better soil structure at the end of the season compared to fertilised ryegrass (Pfert) and the ryegrass/red clover mixture (PR). The increased rooting depth and density of the multispecies swards provided this advantage.
Finally considering earthworm numbers as a proxy for the living component of the soil, there were increased numbers of earthworms in the multispecies swards compared to the fertilised monoculture of ryegrass (Pfert).
Getting Started With A Multispecies Sward
It can be overwelming to change the composition of grasslands swards to incorporate multispecies swards as there are numerous areas of advice available that may not always be applicable to growing these swards in Scotland. A good source of advice relevant to Scotland is the Scottish Farm Advisory Service (FAS) as there is a webpage on Multispecies swards, including a tool to help thinking on the sward mixtures specific to the conditions in your fields https://www.fas.scot/grassland/multi-species-grassland-sward-tool/) and a short video from a farmer who has implemented multispecies swards.
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