Maximising Clover in Grass Swards
9 September 2024
Benefits of including clover in grass swards:
- Increased total dry matter yield
- Increased quality of silage and grazing swards
- Reduced reliance on purchased nitrogen
- Improved biodiversity in swards
- Improved soil health
The use of red and white clovers in farming systems, especially for livestock production, is well recognised in improving forage quality and reducing bagged fertiliser requirements. With recent increases in fertiliser and feed prices and our need to improve soil health, clover leys have become more popular and integral to lower cost forage production.
Both red and white clovers are bred from the same family of beans, Fabaceae, and classed as a legume. It is the ability of the rhizobia bacteria to take atmospheric nitrogen in and convert into a plant-available form which makes clovers so attractive in our farming systems. This self-sufficiency helps to reduce nitrogen fertiliser requirements, which plays an important role in lowering on farm emissions and costs. The protein content of clovers also helps to increase sward quality and silage quality with a homegrown source, increasing livestock performance and reducing the volume of purchased feeds required. In comparison to ryegrass-only swards, both types of clover can maintain their feed quality during summer months providing a higher quality of forage through summer and demonstrating more resilience to drought conditions.
Red and white clover have different rooting systems and growth patterns so require slightly different management strategies to get the best from them as a forage crop. In Scotland, they are best suited to being grown within a grass sward mix to find the balance between improving the sward quality during summer and having a resilient sward which can survive the winter months and tolerate grazing from livestock.
Differences between white and red clover
A summary of the key differences between red and white clover are given below:
| White clover | Red clover | |
|---|---|---|
| Growth habit |  Stolon (multi branch creeping stem) |  Upright growth from a crown at the base of the stem. Tap root, deep rooting |
| Credit AHDB Establishing and Growing Clover | Credit AHDB Establishing and Growing Clover | |
| Strengths | • Grazing and cutting. • More resilient to intensive grazing. • Longer term crop, suited as a companion crop with perennial ryegrass. • Improve seasonality of grass and clover swards during summer. • Increased forage quality and improved dry matter intake of grazing stock. • Reduced nitrogen use. | • Grazing and cutting. • Good companion to a shorter term grass due to poorer persistence and upright growth habit. • Break crop to improve soil fertility and structure. • To improve drought tolerance of swards. • Improve forage quality, in particular protein content of silage. • Reduced nitrogen use. |
| Nitrogen fixation potential @30% sward content | 100-150kgN/ha | 150-200kgN/ha |
| Yield potential | 10-11t DM/ha/yr | 10-15t DM/ha/yr |
| Feed value | 75-82% D Value | 60-70% D Value |
| 12-17% Crude Protein | Up to 11.5MJ/kg/DM | |
| 14-19% Crude Protein | ||
| Grazing and cutting heights | • 5-6 cm • Avoid grazing below 4-6cm | • Cutting height should be 7-8cm to prevent damage to the crown at the base of the stem • Avoid grazing below 6cm |
| Persistency | 8 years + | 3-5 years |
| Animal health challenges | none | • Can cause issues with bloat in cattle • Avoid grazing breeding ewes pre and post tupping |
Establishing clover in swards
Optimum soil fertility is critical to the success of establishing and maintaining clover in a sward. Soil sampling should be carried out every 3-5 years to ensure pH and P&K indices are being maintained at the correct levels.
- Target soil pH for mineral soil is 6-6.2
- The target soil status for phosphate and potash in grassland is moderate (M-/+)
Recommendations for P&K applications for grass establishment from Technical Note 726 – Fertiliser recommendations for grassland are shown below. Additional P&K will be required where soil status is Low or Very Low and rates can be reduced where a status may be High.
Table H. Phosphate and potatsh recommendations for grass establishment (autumn or spring sown) in kg/ha
More information on liming rates and materials can be found at:
fas.scot/downloads/tn714-liming-materials-and-recommendations/
More information on fertiliser recommendations can be found at:
fas.scot/downloads/tn726-fertiliser-recommendations-for-grassland-scotland/
- New leys should be sown into fine, firm seedbeds and ideally rolled after sowing to improve seed to soil contact.
- Red clover is better suited to more free-draining soils due to its deep tap root and ability to scavenge for nutrients and water.
- Include 2-4kg white clover seed or 3kg red clover in a grass/clover sward. Red and white clover can be grown in same mixture with grass and herbs.
- Optimum sowing depth is 0.5 – 1cm. Clover seeds are very small and will not emerge if sown too deep.
- Use small-medium leaf varieties for grazing mixtures and medium-large leaf varieties for cutting mixtures.
- Conduct a soil assessment to check for any issues with soil compaction before sowing.
- Clovers are best sown between April and mid-August to ensure sufficient time for roots to develop before winter.
- Due to a lack of clover friendly herbicide options, weeds should be managed in the year prior to sowing. Using cereals or forage crops in rotation can assist with weed control prior to sowing clover. Consult a BASIS qualified advisor for advice on weed and pest management.
Managing clover to improve persistence
White clover plants will persist for longer than red clovers, a red clover will survive for 3-5 years if managed well. Due to the differing growth habits, each type of clover requires different management. To maximise the persistence and yield of your clovers in grass swards:
- Allow red clover to flower before harvest in its first year of cutting to aid root development and promote rhizobia bacteria. In subsequent years allow the crop to flower at least once in the season.
- Avoid grazing red clover below 6cm or cutting below 8cm to prevent damaging the crown at the base of the stem which stores plant nutrients.
- Avoid grazing red or white clover below 4-6cm.
- Allow 30 days between each cut of silage or grazing event.
- Poaching from livestock or compaction from traffic will affect the persistence of red clover. Be especially careful in wet conditions and winter.
- Maintain soil pH and P&K statuses throughout the life of the sward.
- Limit competition from weeds.
- It is important to manage the canopy of the grass sward in spring to ensure there is sufficient sunlight reaching the base of the sward and emerging clover seedlings – especially important for white clover which has a more prostrate growth habit.
- A clover plant will have small nodules on the root hairs which hold the bacteria which fixes nitrogen. The more nodules a plant has the more nitrogen it can fix.
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Potential issues with clover
When using clovers in livestock systems it is important to be mindful of the risk of bloat when grazing a high clover sward. The risk is greater with red clover swards and higher risk in cold, wet weather or when cattle are hungry. Risk can be reduced by introducing cattle to the sward gradually and providing a supplement such as straw or hay. Avoid changing diets once cattle have been transitioned onto the sward and try to prevent introducing them onto wet swards. If the clover content of the sward is very high, sheep could be used to help keep it under control or reduce the amount of clover seed included in mixes. A bloat oil can be provided through water supplies if the risk is higher. Always monitor livestock closely and consult your vet with any concerns. Red clover silage does not appear to cause any issues with bloat.
Red clover can contain up to 1% of oestrogenic compounds. Oestrogen levels in swards can negatively impact ewe fertility. Breeding ewes should not graze red clover swards for 6 weeks pre- and post-mating to ensure lambing percentages are not affected. Nonbreeding animals can graze red clover swards and silage at any time. Cattle are not affected by these oestrogen levels and white clover does not contain oestrogen.
Clovers offer many benefits to the productivity of forage-based systems but can also have positive effects on the environment by improving the biodiversity in our swards and soils, as a flowering plant providing food for beneficial insects and not least reducing the amount of inorganic nitrogen used to grow grass and grass silage crops. Like all crops they are most successful when grown in rotation and managed as part of the whole farm system rather than a field in isolation. To get the most out of clover swards on your farm ensure:
- Soil fertility and soil structure are suitable.
- You adopt the management practices which apply to the clover type you are growing.
- You have the livestock class and infrastructure to manage clover swards effectively.
Lorna Galloway, SAC Consulting
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