Perennial ryegrass management
Perennial ryegrass pastures are the mainstay of pasture-based dairy farming in southern Australia.
Perennial In most southern Australian dairy farming environments, perennial ryegrass pastures can remain productive for at least four years.
Perennial characteristics significantly lower the cost of production and in a dryland environment, permit growth with minimal intervention as soon as soil moisture allows.
Grows all year - if there is sufficient soil moisture, perennial ryegrass will grow at most times of the year in southern Australia. During the autumn break or when there are significant summer rains an established perennial ryegrass sward can respond almost immediately.
High nutritive value well-managed perennial ryegrass provides high-quality feed of at least 11 megajoules (MJ) of estimated ME per kg of DM for most of the year and rarely below 10 MJ / kg DM. Similarly, crude protein (CP) levels rarely drop below 18-20% DM, except under nutritional or water stress. Overall, perennial ryegrass has better nutritive value than most temperate pasture species.
Minimal disease threat - There are few diseases of perennial ryegrass that significantly affect its productivity or longevity. Ryegrass can be susceptible to fungal rust (also known as crown rust). These types of diseases reduce ryegrass performance but don't usually threaten plant survival.
Minimal pest threat - Few pests can undermine perennial ryegrass performance in Australia. The red headed cockchafer can affect the viability of ryegrass stands, particularly if pasture is not managed to develop and maintain a high volume of roots. In Tasmania, the corbies can have a major impact on perennial ryegrass performance. As with most plants, ryegrass seedlings are vulnerable to the likes of red legged earth mite and lucerne flea during establishment. Although these pests can reduce ryegrass density or growth rates, they generally do not completely destroy the sward.
Ideal for grazing - Perennial ryegrass thrives under good grazing management. Its nutritional qualities are also more forgiving of temporary changes in grazing practices, such as delayed grazing, than other perennial species.
Minimal animal health issues - Recommended soil fertility and fertiliser programs induce few animal health issues with perennial ryegrass. Most can be managed with basic knowledge of ruminant nutrition.
Surpluses can be conserved - As well as being ideally suited to grazing, perennial ryegrass can be conserved for high-quality silage.
Seedling vigour - Ryegrass seedlings have excellent vigour and are relatively quick and easy to establish compared with other perennial pastures.
Broadleaf weed control - Most broadleaf weeds are easily controlled using a selective broadleaf herbicide with minimal impact on ryegrass growth rates. Body of knowledge - The farming community, researchers and service providers know a lot about perennial ryegrass management. See the accompanying factsheets for more information.
Shallow roots - Perennial ryegrass is relatively shallow rooted with almost 75% of the total root mass in the top 10 cm (see Figure 1). Perennial ryegrass is not able to access moisture at depth in the soil, for example where moisture has accumulated at depth over winter, where there are relatively shallow water tables or from irrigation. The shallow root system of perennial ryegrass has been linked to its poor persistence in summer-dry environments.
Low temperature ceiling - While perennial ryegrass performs well at low temperatures, it has a relatively low temperature ceiling compared to other perennial grasses. Beyond the ceiling, growth rates decrease significantly, causing plants to become dormant and possibly die.
Poor summer growth - The combination of shallow roots and a relatively low temperature ceiling means that perennial ryegrass cannot consistently provide significant amounts of quality feed during the hot/dry summer months in southern Australia.
Limited winter growth - The winter production of perennial ryegrass has improved significantly in recent years with a better understanding of rotations, nitrogen use, post-grazing residuals plus more winter-active cultivars. However, growth rates are limited by temperature and sunlight hours. Short rotation ryegrass and winter cereals have a higher potential for winter growth than perennial ryegrass, yet the growth of perennial ryegrass through the winter period tends to be of excellent quality.
Limited ability to defer grazing or cutting - Perennial ryegrass does not store well as a standing sward. There is limited ability to graze or cut a high-quality perennial ryegrass pasture once the ideal stage for grazing has passed.
Tolerance to waterlogging - Although perennial ryegrass can tolerate short periods of waterlogging, if these conditions persist, the lack of oxygen in the root zone will reduce production, and, in extreme cases, cause plant death.
Key approaches to manage ryegrass pasture
- Graze between the 2nd and 3rd leaf stage.
- Maintain a constant cover of green leaf area all year.
- Leave a post-grazing residual of 4-6 cm between clumps, equivalent to 1,500 to 1,600 kg DM per hectare.
Why graze ryegrass between 2nd and 3rd leaf stages?
Perennial ryegrass tillers normally maintain three live leaves.
After being grazed the three leaves are removed. When the 1st leaf emerges again it is produced using sugars stored in the residual stem.
As the 2nd leaf emerges, the plant will start restoring some of the sugar reserves that have been used. The sugar reserves in the plant are fully restored once the 2nd leaf has completely emerged.
Grazing before the 2nd leaf has emerged will limit regrowth rates and threaten plant survival. Grazing after the 3rd leaf has fully emerged will waste pasture and reduce overall nutritional value. Cattle will reject more of this lower value pasture. The drop in nutrition after the 3rd leaf stage occurs faster in the warm seasons (spring-summer) than in winter.
Time your grazing to benefit root growth
The timing of grazing affects root growth. Immediately after a ryegrass tiller is grazed, the growth of the root stops so the plant can use its sugar reserves to grow new leaves. Once the 1st leaf emerges, the root growth will recommence.
Pastures that are grazed too frequently therefore have less root mass. Plants with less root mass are:
- More easily pulled by cattle.
- More vulnerable to hot and dry conditions.
- More susceptible to root-damaging pests (like red-headed cockchafers).
Strengths, weaknesses, opportunities and threats for the use of perennial ryegrass on southern Australian dairy farms (PDF, 1.3MB)
Perennial ryegrass (Lolium perenne) pastures have been, and will continue to be, the mainstay of pasture-based dairy farming in southern Australia in the foreseeable future. The 3030 Project asked the question: If the productive ceiling of perennial ryegrass has been reached what alternatives are available to lift home-grown forage consumption?
The 3030 Project has explored forage alternatives but has also examined perennial ryegrass to gain a better understanding of why it is the cornerstone of pasture-based systems in southern Australia.
This information sheet analyses the key features of perennial ryegrass using a SWOT approach (Strengths, Weaknesses, Opportunities and Threats).
Perennial ryegrass management-grazing management to maximize growth and nutritive value (PDF, 1.1MB)
The 3030 Project reinforced three basic perennial ryegrass grazing management strategies.
- Graze between the 2nd and 3rd leaf stage or before canopy closure.
- Leave a post-grazing residual of 4 - 6 cm between pasture clumps [equivalent to 1500 - 1600 kg DM per ha].
- Maintain a constant cover of green leaf area all year.
These guidelines are not an attempt to present a silver bullet for perennial ryegrass pasture management. They are not meant to be exclusive; using other guidelines based on similar principles can also achieve success in maximising the growth of high quality pastures and minimising waste.
Perennial ryegrass management II - practical application of grazing principles (PDF, 1.1MB)
How to achieve the ABC targets in practice. There are four main areas of perennial ryegrass management that should be covered in order to achieve the ABC targets:
- Set rotation length in relation to Leaf Emergence Rate (LER) and monitor it.
- Choose the paddocks to be grazed and assess their pre-grazing cover.
- Adjust supplementation and/or close for conservation to achieve the target rotation length and post-grazing residuals.
- Make daily adjustments to the allocated grazing area in order to achieve the target pasture intake and post- grazing residuals.
Perennial ryegrass management IV -grazing management specific practices (PDF, 860KB)
This Information Sheet focuses on paddock-level specific grazing management practices. These practices should be understood within the context of the three basic strategies identified by the 3030 Project as the basis for pasture management (discussed in the grazing management to maximize growth and nutritive value Information Sheet).
Perennial ryegrass management VII - pasture renovation (PDF, 827KB)
Contents: Decision process leading to the renovation or over-sowing of perennial ryegrass pastures on southern Australian dairy farms. The focus of this factsheet is on:
- Monitoring and assessment of pasture stands.
- Decision criteria to choose renovation or an alternative.
- Full renovation.
- Objective assessment of pasture leads to more informed decisions about renovation.
- Decisions about pasture renovation should be based on recent paddock performance and the chance of the pasture recovering, taking into account the role of the pasture in the dairy system.
- In Project 3030, oversowing perennial ryegrass with more perennial ryegrass was more successful than oversowing with Italian or hybrid ryegrass.
- A full renovation program should not only take into account sowing the new grass but also address the temporary feed shortages that are caused by slow establishment of perennial pastures. Forage cropping may help to address this.