El raigras

Perennial ryegrass (Lolium perenne)
Paul Sanford, DAFWA

Features
• highly nutritious and palatable perennial grass • with good management can be very productive in suitable environments • excellent seedling vigour • high temperatures constrain summer growth • low drought tolerance, so best suited to fertile soils (>600 mm) • requires rotational grazing for persistence, high yields and tomaintain nutritional quality. Perennial ryegrass is one of the most valuable pasture grasses for temperate regions of the world. It is a native of Europe, temperate Asia and north Africa and was introduced into Australia in 1803. Under favourable conditions perennial ryegrass can produce large amounts of high quality feed throughout the growing season. It grows predominantly from the autumn breakuntil late spring, but can make useful growth in summer if it receives substantial amounts of out-of-season rainfall or irrigation. Summer growth is restricted by high temperatures (>30°C), even if sufficient moisture is available. Perennial ryegrass has low drought tolerance and a relatively shallow root system. As a result, its role in WA is limited to fertile soils in high rainfall areas andirrigated pastures.

Seasonal growth pattern

Growth

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Description • tussock-forming perennial up to 60 cm in height with a fibrous root system • dark-green foliage, leaf blades are hairless, flat, upper surface evenly ribbed, lower surface smooth and shiny. Length to 30 cm, width to 7 mm. Young leaves normally folded in the bud, with a V-shaped cross-section • ligule membranous,white, transparent, shorter than wide. Auricles small and narrow • leaf sheath hairless with fine longitudinal ribs as in leaf blades, base of sheath may be reddish-purple • inflorescence is an erect narrow spike up to 20 cm long to which the spikelets are attached alternately, on opposite sides of a wavy stalk.

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Temperate perennial grassesSoil–climate adaptation Rainfall (est.): >600 mm (south coast >500 mm) Season length: >8 months Drought tolerance: Low Frost tolerance: High Soil type: Well-drained medium- to finetextured. Coarse-textured soils tend to dry out too much during summer Soil fertility requirements: High Soil pHCa: >4.0 Aluminium tolerance: Sensitive (but varies with cultivars)

Waterlogging tolerance: Low tomoderate Salt tolerance: Slight to moderate Nutritive value DMD: 56-85% ME: 7.8-12.3 MJ Crude protein: 8.0-27.7% Environmental benefits Groundwater recharge control: Low, as perennial ryegrass does not develop a deep root system. The roots are short-lived, with most dying over summer and regrowing the following autumn.

Establishment
Perennial ryegrass is relatively easy to establish due to itsexcellent seedling vigour, however it is still necessary to minimise weed competition. It should be sown into a prepared seedbed or direct drilled at 6 kg/ha which should give about 240 viable seeds/m2 based on 530,000 seeds/kg and a minimum germination rate of 75%. It is best not to sow other perennial grasses with perennial ryegrass due to its highly competitive nature. Perennial ryegrass is sown inautumn no deeper than 10 mm.

The condition is caused by the endophyte fungus (Neotyphodium lolii), which produces the toxic compound lolitrem B. If ryegrass staggers occurs stock need to be moved quietly to a non-toxic area and/or given supplementary feed. The ‘do-nothing’ approach is also viable as most stock recover. The endophyte causes a range of animal problems including reduced growthrates and milk production. Endophytes can be eliminated by storing seed at 20-25°C for 18-24 months.

Management
The first grazing of perennial ryegrass should be delayed until seedlings are firmly established and feed-on-offer has reached about 1800 kg DM/ha to avoid stock pulling plants out of the ground.

Livestock disorders
A disorder called ‘ryegrass staggers’ can occur in livestock grazing...