Well managed grassland can deliver high quality feed at a low cost for livestock farms in Scotland. It forms the largest crop area in Scotland and can provide forage all year round regardless of where you are. There are many elements to good grassland management, this guide will concentrate on the considerations that go into establishing and managing a new ryegrass ley.
Choosing a grass mixture
There are 4 types of ryegrasses which form the basis to grass mixtures sown in the UK:
- Perennial
- Hybrid
- Italian
- Annual
These ryegrasses will have slightly different growth habits, but the main difference is their lifespan. An annual ryegrass will typically only survive 12 months, it is very fast to establish and will be high yielding within that year, conversely a perennial ryegrass is slower to establish and has a more level growth curve but if managed well it could be 8 years before there are major drops in yield.
A ryegrass cell will be either a Diploid or Tetraploid. This refers to the number of chromosomes within that cell. You may see a ‘T’ beside varieties denoting whether it is a tetraploid or diploid.
When choosing your grass mixture in order to get the most suitable mixture you should make the following considerations:
Variety Choice
Ensure the varieties in your grass mixture are on the recommended grass and clover lists and that the mixture is meeting industry standards for germination and weed seed screening.
Soil Type
If you have very light soils which are prone to drought or erosion tetraploids may be better suited to these fields as they have a deeper rooting system. Inclusion of different species such as festuloliums or cocksfoot in the mixture may also help with improving the resilience of those swards
Diploid grasses will be better suited to heavier soils, their ability to tiller out and provide a dense base will help with improving the swards ability to protect the soil from poaching or tracking.
Longevity
Identify how long you want your sward to persist, a shorter term grass may suit if you are on a short rotation between re-seeding or using in between forage crops, a hybrid may provide high yielding silage crops for a shorter period of time or if it is a grazing field a perennial ryegrass will give the best longevity.
Use
It is important to identify if the sward will be used mostly for grazing, cutting or a combination of both. This will influence the proportion of diploid and tetraploid grasses which go into the mixture and if including clover the size of clover leaf which is best suited to the purpose. Swards with more diploid grasses have typically been used for grazing due to their dense sward and tetraploids have been used in cutting mixtures as they have a more upright growth habit.
Field Characteristics
If you have a challenging site for your reseed which has steep slopes, rocky outcrops or more peat soils then inclusion of different species such as timothy or creeping red fescues can help to minimise any gappy areas where ryegrass may struggle.
Clover or no clover
It is important to establish what the purpose of your sward will be to identify which type of clover is best suited to that mixture. White clover is better suited to more intensive grazing, whilst red clover with its upright growth habit can complement shorter term grasses for silage effectively. Clover varieties have different size leaves with smaller leaves more suited to grazing and larger leaf varitieties more suitable for cutting.
Soil fertility
Soil fertility is critical to the success of any newly sown grass sward. Soil samples should be taken routinely every 3-5 years and ideally at least 12 months in advance of sowing a new sward to ensure that if applications of lime, phosphate or potash are needed then there is sufficient time for these to be made and for them to take effect.
Soil pH
The availability of nutrients, levels of biological activity in soils and success of many crops are dictated by the acidity of the topsoil. Maintaining optimum pH in topsoil is critical in achieving optimum yield, forage quality and preventing losses of nutrients to the environment.
- Target soil pH for mineral soil is 6-6.2
- Target soil pH for a peaty soil is 5.3-5.5
Applications to increase soil pH should be made at least 6 months in advance of sowing a new crop to allow time for soil levels to increase and liming should be completed before any phosphate applications to limit phosphate lock up.
More information on liming rates and materials can be found at fas.scot/downloads/tn714-liming-materials-and-recommendations/
Phosphate and potassium
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 A. Phosphate and potash recommendations for grass establishment (autumn or spring sown) in kg/ha
When calculating the amount of phosphate required the phosphate sorption capacity (PSC) should be considered. The PSC varies depending on soil texture, soil chemistry, soil pH and organic matter levels - it reflects the ability for differing soils to bind with applied phosphate. You can find out the PSC level for your farm using a thematic map provided at Map of soil phosphorus sorption capacity | Scotland's soils (environment.gov.scot)
Table B. Effects of PSC on annual fertiliser adjustments (kg P205/ha)
For example, a moderate status soil with high clover content and classed as PSC3 would require 70kg of P205 (table H) plus an additional 20kg (Table K).
Soil preparation
New grass should be sown into a fine, firm and clean seedbed to maximise seed to soil contact and germination. The decision on how to achieve this optimal seedbed will depend on many factors such as previous crop, timing, topography, availability of equipment and soil type. Whether this preparation includes a full cultivation with a plough or chemical spray off and direct drill the aim is to provide the conditions for that seedling to germinate and establish quickly with minimal competition from weeds. Issues such as soil structure, soil fertility, emerging weeds, surface trash, pests and weather can affect the speed of development. Newly sown leys will require a warm soil and moisture to germinate so timing of sowing to coincide with soil temperatures above 10 degrees and sufficient moisture will assist with creating the soil conditions to give your sward the best start.
The physical condition of soils should be assessed before sowing to ensure there are no issues with compaction which would impact plant rooting, nutrient cycling and water filtration. To find out more about identifying and addressing compaction please visit fas.scot/downloads/farming-better-climate-practical-guide-alleviating-soil-compaction/.
Grass seed mixtures are typically sown at 18-37kg/ha but this will vary according to the type of ryegrass and whether the varieties are a tetraploid or diploid. Tetraploids are larger seeds and typically require a higher sowing rate as it takes more seeds to make a kilogram. The recommended sowing rate will usually be shown on the label.
Seeds shown be sown at a depth between 1-2cm. If seeds are sown too deep it will take them longer to establish, giving weeds longer to get established and compete with the grass seedling.
It is recommended that crops are rolled after sowing to improve the seed to soil contact, retain moisture and improve germination.
Post emergence weed control
There are currently very few clover friendly herbicide options available in the UK to control weeds. If you have included clover in your ley, preparation is key to giving the new sward a chance to compete with weeds. This preparation includes optimum soil fertility, choosing the grass right mixture for the right situation, seedbed preparation and timing of sowing.
If the weed burden in the new ley justifies herbicide treatment you should consult a BASIS qualified agronomist to get advice on the most suitable product to use on your crop.
Grazing with sheep and topping may be alternative options to consider if there is clover in the sward which may be damaged from herbicide treatments. Topping should only be carried out when the new sward passes the ‘pull test’ – this is when you can grab a section of grass and pull without the plant coming out from the roots. If topping the mower should be set at approximately 8cm to prevent damaging the sward.
A grass sward will persist for longer and achieve higher yields with higher plant populations. Management in the first 5-6 weeks after sowing is important to ensure the maximum number of ryegrass plants can establish a strong root system, keeping weeds and weed grasses out of the sward.
Management in the first 12 months
First graze
The first graze of a new sward will depend on how quickly the crop establishes, but the first graze must not be before the grass plants pass the ‘pull test’ - this is when you can grab a section of grass and pull without the plant coming out from the roots. The first grazing should be with animals with smaller mouths and hooves, ideally sheep or lighter calves to prevent any poaching of the sward. Until the roots of the new grass plants are well established the soil may be sensitive to poaching and heavy machinery so avoid cutting or grazing heavily in wet conditions.
Weed Control
Ingress of weeds may be inevitable during the life of your grass sward but avoiding poaching, over grazing or under fertilising a grass sward will help prevent the space and opportunity for weeds to get established. Ensuring the sward has the nutrition to out compete any weeds or respond to challenges such as drought or wet conditions.
Encouraging clover and grass tillering
Clovers are slower to establish than a perennial ryegrass and are more sensitive to lower soil temperatures. It is important if sowing a late Summer or Autumn reseed to give the clover plants enough time to develop their roots fully before grazing – this may delay the time between sowing and first graze taking that field out of production for longer.
Due to the prostrate growth habit of clovers, they are very sensitive to shading out by high grass covers. It is important to manage the canopy of the grass sward to ensure there is sufficient sunlight reaching the base of the sward without over grazing the grass plants. A clover plant will lie dormant for longer in spring in comparison to a ryegrass and if it does not receive enough nutrition and sunlight the small clover plants will not regenerate resulting in fewer clover plants. This will not become evident until later in the summer when the clover is growing more actively.
If a grass plant is grazed too low, it uses energy from its root reserves to develop new leaves to enable it to intercept sunlight and grow from photosynthesis. If grazed too low, it can take longer to recover and make the grass plant less competitive. New swards should be grazed to approx. 5cm in the first year to balance the development of clover and grass plants. Avoiding cutting a ley in its first year will give it longer to establish stronger roots and to tiller more effectively.
A ryegrass plant produces daughter tillers in the Spring and Autumn, these daughter tillers are the future grass plants for the following Spring and Autumn so careful canopy management will ensure the daughter tillers get enough sunlight to develop and minimises the dead material which builds up at the base of the sward and compromises yield and quality of the sward.
Ongoing management
Ongoing management of weeds, grazing, frequency of cutting and soil fertility will help to ensure that the yield is maximised for as long as possible and provide maximum economic return on reseeding.
Lorna Galloway, SAC Consulting
Related Resources
Grassland Productivity Grazing Management Video
Alleviating Soil Compaction Practical Guide – Farming for a Better Climate (fas.scot)
Technical Note (TN714): Liming Materials and Recommendations
Technical Note (TN765): Recommended Grass and Clover Varieties 2023 - 2024
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