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Characteristics of Ryegrass

Ryegrasses are the most widely grown cool- season grasses in the world. They have numerous desirable agronomic qualities. They establish rapidly, have a long growing season, are high yielding under favorable environments when supplied with adequate nutrients, posses high nutrient contents, and can be used for grazing, hay, or silage. Ryegrasses grows best on fertile, well- drained soils but can be grown on soils where it is too wet at certain times of the year for satisfactory growth of other grasses. Ryegrasses are heavy users of water and will perform less than optimum during a drought or periods of extended low or high temperatures. They are indigenous to Europe, Asia, and North Africa, but are grown world wide. The ryegrasses are considered to be high quality forage and their high digestibility makes them suitable for all types of ruminants.


Types of Ryegrass and Adapted Varieties

The two most important ryegrass species are Italian ryegrass (Lolium multiflorum Lam.) and perennial ryegrass (Lolium perenne L.). Traditionally, Italian ryegrass would not survive for more than a single growing season in northern climates. However, new experimental varieties from Switzerland have shown no stand loss after three production years in Pennsylvania. Italian ryegrass has a bunch-type growth (lacks rhizomes) and flowers in day lengths greater than 11 hours. There is no winter or cold weather requirement for Italian ryegrass to flower and therefore will flower throughout the summer. Italian ryegrass is not widely recommended as a forage crop in Pennsylvania because available varieties will not survive Pennsylvania winters.

Perennial ryegrass is also a bunch-type grass but generally will survive for several growing seasons in Pennsylvania. Unlike Italian ryegrass, perennial ryegrass requires a dormancy period of cool temperatures before the photoperiod can induce flowering and therefore will normally produce seedheads only once per year during the late spring. However, researchers at Penn State have observed seedhead production by perennial ryegrass during mid-summer regrowths. Perennial ryegrass can withstand considerable grazing mismanagement and remain productive. Unfortunately, perennial ryegrass has proven to be slightly less persistent in Pennsylvaina's climate than other cool-season grasses such as orchardgrass, tall fescue, and timothy.

Within the Italian and perennial ryegrass species there are two basic groups, the diploids and tetraploids. The distinction between the two groups is based on the number of chromosomes within each plant cell. In the diploid ryegrass cells, each chromosome is present twice; however, in the tetraploid ryegrasses cells each chromosome is doubled and is present four times. Tetraploid perennial ryegrasses have larger leaves, fewer but larger tillers, produce a more open (less ground cover) growth, and are more suited for production ina legume mixture than the diploid perennial ryegrasses. Tetraploids have a higher percentage of sugars in the forage than diploids, which explains their higher digestibility and grazing preference over diploids. Both the seed and seedlings of tetraploid varieties are larger, but the growth following emergence and persistence is often greater for diploid varieties.

Numerous tetraploid perennial ryegrasses have been tested in Pennsylvania variety trials, including Grimalda, Bastion, Reveille, Citadel, Nestor, and Taptoe. Grimalda matures 10 to 14 days earlier than Bastion, Reveille or Nestor. Citadel and Taptoe mature later than these varieties.

Grimalda was one of the first ryegrass varieties marketed in Pennsylvania. Unfortunately, it matured earlier than most alfalfa varieties with which it was seeded and reduced the forage quality when the mixture was harvested based on alfalfa maturity. The experience with this early maturing variety resulted in producers concluding that all ryegrasses were not adapted to their system, a conclusion from which perennial ryegrass is now starting to recover.

Natural hybridization between the Italian and perennial species has occurred frequently. Persistence of hybridized ryegrasses is intermediate between the parents. Therefore they are frequently referred to as "short rotation ryegrasses" in recognition of their lack of persistence compared to perennial ryegrass. In addition, flowering in the hybridized ryegrasses is similar to that of the Italian species in that there is no dormancy requirement for flowering and tillers will continue to flower sporadically throughout the growing season. Bison, a hybridized ryegrass, has been tested in Pennsylvania and matures in the spring about 10 days later than Grimalda.


Ryegrass Establishment

Normal winter temperatures in Pennsylvania are mild enough to allow ryegrass seeding in either the spring (April or May) or late summer (before August 15 and 25 in northern and southern Pennsylvania, respectively). Ryegrass may be seeded alone; however, to improve hay yields when growing ryegrass a mixture with a legume is recommended. Legumes, such as alfalfa or white clover in the mixture will also provide some nitrogen to the ryegrass and can also improve the quality of forage produced. Ryegrass seedings have been successful in both a clean, tilled seedbed and in existing grass sod. However, when no-till seeding, the existing grass sod should be mowed or grazed very short or desiccated with a chemical prior to seeding to reduce competition. Ryegrass should be band seeded 0.25 to 0.5 inch deep. If the seedbed is dry and press wheels are not used, cultipack before and after seeding for additional stand insurance.

Ryegrass seeding rates depend on its intended use and the condition of seedbed. When seeding into a well-prepared seedbed, 15-20 lb per acre is recommended. When seeded with a compatible or adapted legume (alfalfa, birdsfoot trefoil, and white or red clover) 4-8 lbs per acre is recommended. In a USDA-ARS Pasture Research Laboratory study, alfalfa yield was not effected by ryegrass seeding rate (6 to 18 lbs per acre) in late summer seedings of alfalfa-ryegrass mixtures. In the same study, alfalfa became the dominant species within one year regardless of seeding mixtures, even when seeding rates heavily favored ryegrass establishment.


Ryegrass Harvest Management

Seeding year harvest management of perennial ryegrass is dependent on time and method of seeding, fertility, growing conditions, and other factors which effect rate of establishment. However, with favorable establishment and growing conditions one or more harvests are possible in the seeding year. First time harvest or grazing on newly established ryegrass should be delayed until it is 10 to 12 inches tall.

As a hay crop, ryegrass yields may be relatively low unless considerable time is allowed for forage accumulation for fall harvest. Ryegrass plants contain less dry matter and therefore require longer curing time before baling relative to other cool season grasses. In addition, they are more difficult to mow with a sickle bar mower than other grasses.

Established ryegrass pastures can be initially grazed when spring growth reaches 2 to 3 inches in height and the pasture does not risk excessive damage due to wet soil conditions. It may be continually grazed but yield and plant persistence are compromised if it is continuously grazed below 1.5 inches in height. Greater yields are possible when ryegrass is rotationally grazed. A grazing system which allows 7 to 10 inches of regrowth between grazings will benefit grass yield as well as persistence. Animals should be removed from rotationally grazed pastures when the ryegrass stubble is from 1.5 to 2 inches in height. Under grazing, perennial ryegrass-alfalfa mixtures are superior to orchardgrass-alfalfa mixtures in production of crude protein, digestible dry matter, and alfalfa persistence.


Ryegrass Fertility

Soil pH for optimum ryegrass production is between 6.0 and 7.0; however, ryegrass has been grown at pH of 5.0. Determine fertility and lime needs by soil testing, but in the absence of a soil test on soil with a medium-fertility level, plow down 0-45- 135 lb per acre and apply 20-20-20 lb per acre at seeding (banded if possible) when seeding without a legume. When seeding ryegrass with a legume, apply none or less than 20 lb per acre of nitrogen at seeding. Nitrogen application in excess of 20 lb per acre will stimulate ryegrass development and inhibit legume establishment. On well adapted soils, ryegrass is very competitive with other grasses, legumes, or weeds.

A soil test is the best guide for proper fertilization of established ryegrass. Do not apply fertilizers in excess of soil test recommendations because nutrient imbalances may occur in animals consuming the ryegrass. Ryegrass responds very well to nitrogen fertilization which is very important for economical production. Profitable economic returns over investment can usually be obtained with applications of 150 lbs of N per acre per year. It should be applied in split applications of 50 to 60 lbs per acre in the spring with the remaining amount being evenly divided and applied after each grazing or cutting. Seeding mixtures of ryegrass and a legume reduces the need for nitrogen fertilization. Applying high rates of nitrogen (in the form of manure) to alfalfa-ryegrass mixtures, caused ryegrass to dominated; however, ryegrass was less suppressive than orchardgrass in alfalfa mixtures when manure was added.


Ryegrass Summary

Ryegrasses have numerous desirable agronomic characteristics. They establish rapidly, have long growing seasons, are relatively high yielding in suitable environments, have high nutritive value, and can be used for grazing, hay, or silage. However, the lower persistence of perennial ryegrass relative to other cool-season grasses and the increased drying time of ryegrasses should be considered prior to their use. The use of ryegrass as a part of a forage production system should be carefully evaluated. Ryegrass does not fit into every farming operation but should be considered as a viable options on many Pennsylvania farms, especially those which include grazing as a harvesting method.


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This page was last updated on November 16, 2002