Perennial Ryegrass for Forage in the USA

Perennial ryegrass (Lolium perenne L.) is a temperate, perennial forage grass noted for fast establishment, exceptional quality, and high cool-season productivity. It is folded in the bud, with dark green, glossy, smooth, glabrous, prominently ridged leaf blades. The collar is narrow with small, claw-like auricles and a 0.5- to 2.5-mm thin-membranous, obtuse ligule. Leaf sheaths often are reddish at the base. Flowering culms are 50 to 100 cm with a spike-type inflorescence with 5 to 40 sessile, awnless spikelets positioned edgewise to the rachis. Perennial ryegrass is adapted to mild, wet climates or irrigated regions. It is tolerant of poorly drained soils with a pH range of 5.0 to 8.3. Optimum growth occurs between 20 and 25°C. It is less persistent than other perennial, temperate forage grasses, but because of its high quality is widely used in dairy (Bos taurus) and sheep (Ovis sp.) forage systems; primarily for pasture and silage. Seeding rates vary from 18 to 24 kg ha−1 in pure stands, reduced to 12 to 18 kg ha−1 in mixtures. Depth of planting is 0.5 to 1.25 cm. High levels of fertility are required for high yields and stand persistence. Economical N application levels are in the range of 160 kg N ha−1 yr. Defoliation management during vegetative growth should allow plants to attain a height of 10 to 25 cm prior to grazing but not shorter than 2.5 cm (6 cm for mechanical harvest). When plants enter the reproductive growth phase, clipping or grazing should avoid removal of elevated growing points until boot stage. Currently, lack of persistence and sensitivity to high temperature and drought are the main limitations to expanded use of perennial ryegrass in the USA.