Annual Ryegrass

Images of Annual Ryegrass

Summary

Other common name: Italian Ryegrass
Winter-annual grass
Introduced from Europe, naturalized in California
Lolium multiflorum cvs include 'Astor' for coastal areas and 'Oregon Common' from the
Willamette Valley, cultivars of Lolium rigidum include 'Wimmera 62' for low-rainfall areas
Does well on heavy, waterlogged soils
About 36-48" tall
Biomass about 4,700-8,500 lb/acre
N content about 1.3%
Flowers May-June
Often volunteers in vineyards, orchards on high-fertility sites
May compete excessively with grape vines, necessitating intense mowing regimes

Common Name

This species has been termed annual ryegrass (Finch & Sharp, 1983), Italian Ryegrass (Munz, 1973) (McLeod, 1982), and Australian or common ryegrass (USDA-SCS. 1973).

Scientific Name

The scientific name for annual or Italian ryegrass is Lolium multiflorum Lamarck (Munz, 1973). For Wimmera ryegrass, the scientific name is Lolium rigidum Gaud. (Slayback, pers. comm., Finch and Sharp, 1983).

Cultivar

'Astor' was selected for high forage yield and quality in coastal areas of Oregon and Washington (USDA-SCS, 1973). In general, only spring types of annual ryegrass should be used in California (Miller et al., 1989). 'Wimmera 62' was selected for use in areas of relatively low humidity and rainfall in California (USDA-SCS, 1973).

Prine (1991) reported that "common ryegrass" originally referred to seed from Oregon ryegrass accessions produced in the northwestern USA. However, the term has come to include all unnamed or uncertified Italian ryegrass (annual ryegrass) seed.

Seed Description

Annual ryegrass averages about 217,000 seeds/lb. (USDA-SCS, 1973). Common annual or Italian ryegrass has awns, whereas 'Wimmera-62' is awnless (Slayback, pers. comm.; Finch and Sharp, 1983).

Seedling Description

Seedling vigor is good (USDA-SCS, 1973), and the grass is very competitive (Slayback, pers. comm.). Annual ryegrass has faster seedling establishment and greater seedling vigor than does perennial ryegrass (Miller, 1984). 'Wimmera 62' also shows strong seedling vigor (Finch and Sharp, 1983).

Mature Plant Description

Plants are yellowish-green at the base. Glossy leaves attain up to 12-inch length. Awned multiple florets are carried close to and alternating along a zig-zag rachis up to one foot long (USDA-SCS, 1973). Both annual and perennial ryegrasses are bunch grasses (Miller, 1984).

Temperature

This is a cool-season annual grass that is cold tolerant (Peaceful Valley, 1988) although neither Lolium multiflorum nor Lolium perenne is as winter hardy as timothygrass or orchardgrass (McLeod, 1982; Miller, 1984). Annual ryegrass will germinate in cooler soils than most other cover crop and pasture seeds (Peaceful Valley, 1988).

Geographic Range

Annual or Italian ryegrass is naturalized throughout much of California, mostly at lower elevations (Crampton, 1974). In general it is suitable for elevations below 3,000 ft. (Slayback, pers. comm.) and is best adapted in coastal areas with long seasons of cool, moist weather and in excess of 12 inches rainfall (USDA-SCS, 1973).

Lolium multiflorum and Lolium perenne are tolerant of a wide range of soils and climates. They will tolerate temporary floods, and do better than small grains on wet soils, but perform best on well-drained soils (Miller, 1984).

Lolium multiflorum and Lolium perenne will grow on sandy soils if they are well fertilized, but do better on heavier clay or silty soils with adequate drainage. (Miller, 1984). Annual ryegrass can be used as a green manure crop in rotations. (Miller, 1984). 'Wimmera 62' is well adapted below 3,000 feet (Finch and Sharp, 1983.)

In rural roadsides of the South Sacramento Valley, annual ryegrass prevails at the pavement edge where runoff augments the water supply. Wild oat dominates the drier recovery area. Annual ryegrass also abounds in moist sites, including ditches. (R.L. Bugg, pers. comm.)

Water

This species tolerates extended wet periods (Hofstetter, 1988); short periods of flooding will not damage a stand, but long periods will (McLeod, 1982; Peaceful Valley, 1988).

In general, annual ryegrass is adapted to irrigated farming on well-drained land (McLeod, 1982). Lolium multiflorum and Lolium perenne will grow on sandy soils if they are well fertilized, but do better on heavier clay or silty soils with adequate drainage (Miller, 1984).

Annual ryegrass has very vigorous seedlings, and provides rapid ground cover. It can be used as a cover crop in grass waterways or flood canals or on cropland subject to flooding (Miller, 1984). 'Wimmera 62' is suitable for use in areas of relatively low humidity and rainfall, but does best a minimum of 12" of rainfall (USDA-SCS, 1973). It is more drought tolerant than common ryegrass, but also does well where water ponds (Finch and Sharp, 1983).

Nutrients

Annual ryegrass has a low requirement for lime (McLeod, 1982) and can assimilate as much as 200 lbs N/acre/yr (Graves and Munoz, 1987). It is considered a heavy user of N and often responds favorably to added P on eroded soils. Typical fertilizer application on new critical area and lawn seeding is 100 lbs nitrogen and 50 lbs phosphoric acid (P2O5) per acre worked into the soil surface during seedbed preparation (USDA-SCS, 1973). Continued heavy production of hay or pasture will require 75 to 100 lbs/acre of nitrogen each fall (USDA-SCS, 1973). Phosphorus and potassium are critical when annual ryegrass is grown with a legume (Riewe and Mondart, 1985). 'Wimmera 62' has lower fertility requirements than common ryegrass (Finch and Sharp, 1983).

Soil pH

This grass tolerates acidic to moderately alkaline soils (USDA-SCS, 1973); the pH range is 5-8, with the optimum between 6 and 7 (Riewe and Mondart, 1985).

Soil Type

Common annual ryegrass is adapted to many soil types (Hofstetter, 1988) and has been touted as viable on any soil type (McLeod, 1982; Peaceful Valley, 1988) but does best on loams or sandy loams. It is commonly used on poor soils or on sandy or rocky soils where it will normally produce a better growth than will cereal species (Miller et al., 1989). It can also tolerate clays or clay loams and attendant poor drainage (Slayback, pers. comm.). Lolium multiflorum and Lolium perenne will tolerate a wide range of soils and climates, withstand temporary floods, and do better than small grains on wet soils, but perform best on well-drained soils (Miller, 1984). They will grow on sandy soils if they are well fertilized, but do better on heavier clay or silty soils with adequate drainage (Miller, 1984)

'Wimmera 62' grows on soil types ranging from sandy loams to clays, but medium to heavy textures are best. This variety is recommended for areas of marginal soil fertility (USDA-SCS, 1973). It tolerates sites with poor drainage (source). It is well adapted to all orchard and vineyard soils below 3,000 feet (Finch and Sharp, 1983) and is suitable for heavy soils where its high biomass production is not a problem (Finch and Sharp, 1983).

Shade Tolerance

Annual ryegrass is shade intolerant (Riewe and Mondart, 1985)

Annual ryegrass shows excellent performance in mature pecan orchards (in Southern Georgia) which have little shade from late November until mid-April (Bugg, R.L., pers. comm.).

Salinity Tolerance

No information was available on the salinity tolerance of annual ryegrass.

Herbicide Sensitivity

Annual ryegrass can be controlled using weed oil or non-persistent contact herbicides (SCS, 1973), including glyphosate (Bugg, pers. comm.). Chlorsulfuron (Telar) inhibits germination of annual ryegrass (Lanini, pers. comm.) and can be used to reduce this plant as a weed in native perennial grass stands.

Life Cycle

Common annual ryegrass has biennial tendencies in the northeastern states where it will grow vigorously until dormancy, survive winter, regrow quickly in spring, and produce seed by mid-June (Hofstetter, 1988). Under farm conditions, few of the plants live more than one year, so the species is generally considered an annual (McLeod, 1982). In California, this grass is a cool-season or winter-growing annual (USDA-SCS, 1973).

Seeding Rate

Seeding rates vary depending on the intended use, the seeding technique, and the authority. In general, because annual ryegrass does not tiller much, relatively high rates of seeding are recommended, despite the relatively small seed (Miller et al., 1989). For ryegrass used as a cover crop, seeding rates range from 9 lb/acre (Finch & Sharp, 1983) to 10 to 15 lbs/acre (Miller et al., 1989) to 20-25 lb/acre (Peaceful Valley, 1988; Hofstetter, 1988) to 25-35 lb/acre (McLeod, 1982). Slayback (pers. comm.) suggests that 9lbs./acre (80% Pure Live Seed) is adequate if broadcast, 6 lbs/acre drilled. Recommended seeding rates (USDA-SCS, 1973) in lbs/acre of viable seed are:

    Pasture, Cover Crops, Burns, and Wildlife Habitat: Drilled - 5 lb., Broadcast - 10 lb.
    Critical Area Plantings: Drilled - 15 lb, Broadcast - 30 lb
    Temporary Turf: Precision Seeded - 60 lb, Broadcast - 120 lb
    Overseeding Bermuda Turf: Precision Seeded - 60 lbs - 120 lb

Other recommendations include 16-22 kg/ha (Riewe and Mondart, 1985), 40 kg/ha for erosion control (Riewe and Mondart, 1985). And the suggestion by Miller (1984) that both annual and perennial ryegrasses should be sown at 20-28 kg/ha (18-25 lb/a) for pure stands, and 11-17 kg/ha (10-15 lb/a) if sown along with a legume or a small grain.

Crimson clover can be grown in conjunction with annual ryegrass. When sown in combination with companion crops, crimson clover is usually sown at 2/3 the normal rate, and the other crop at 1/3 the monocultural rate. Developmental rates of annual ryegrass and tall fescue are similar to that of crimson clover (Knight, 1985).

Seeding Depth

3/4 inch (McLeod, 1982)

Recommended depth for common annual, 'Wimmera 62' and perennial ryegrasses is one-half inch (USDA-SCS, 1973; Finch and Sharp, 1983; Miller, 1984).

Seeding Method

Seeding procedure is to loosen surface soil, followed by smoothing and firming. Both annual and perennial ryegrasses can be seeded into bermuda grass sod (Miller, 1984). On highly-erodible slopes, 3,000 to 4,000 lbs per acre of straw can be applied as a surface mulch following seeding and fertilizing to hold soil and seed in place until a stand is established. Annual ryegrass is much used to "hydroseed" steep critical areas using mixtures of seed, fertilizer and commercial wood fiber mulch in water (USDA-SCS, 1973). This procedure is becoming less popular in light of the tendency of annual ryegrass to compete with native grasses (Bugg, pers. comm.).

'Wimmera 62' should be seeded on a prepared seedbed, and seed should then be covered (Finch and Sharp, 1983).

In New York state, several cover crops were evaluated after overseeding into corn 6-18" high: ryegrass and medium red clover + ryegrass have performed well (Scott and Burt, 1985).

Seeding Dates

In the Pacific Coast and southeastern states, annual ryegrasses should be seeded in the fall (McLeod, 1982; Finch & Sharp, 1983; Riewe and Mondart, 1985). In the northeastern states, seeding can be in early spring, late summer, or early fall (40 days before killing frost) (Hofstetter, 1988). McLeod (1982) recommends sowing in the spring in the north to avoid freeze damage. When overseeding into corn, seed at last cultivation or anytime thereafter or immediately after corn silage harvest (Hofstetter, 1988). When overseeding into soybeans, seed at leaf-yellowing (Hofstetter, 1988).

Inoculation

Annual ryegrass is not a legume and requires no inoculant (Bugg, R.L., pers. comm.)

Seed Cost

Seed is relatively inexpensive (USDA-SCS, 1973; Finch & Sharp, 1983; Peaceful Valley, 1988; Miller et al., 1989)

Seed Availability

Seed is generally plentiful for both annual and perennial ryegrasses (Finch & Sharp, 1983; Miller, 1984; Miller et al., 1989). Certified seed of cvv 'Astor' and 'Wimmera 62' became available on the West Coast during the '70's (USDA-SCS, 1973).

Because L. multiflorum cross-pollinates readily with other Lolium species, seed sold as annual ryegrass may be contaminated. Relatively-pure seed may be procured from certified variety named lots (USDA-SCS, 1973). Sources are listed in: Southern Seedsmen's Association, 1989 Directory and Buyers' Guide (40th Ed). SSA, Alexandria, Louisiana, 268 pp. (Bugg, pers. comm.)

Days to Flowering

Annual (Italian) ryegrass flowers from June through August, according to Munz (1973). This is later than wild oat or ripgut brome. By comparison with the latter two grasses, annual ryegrass is usually restricted to moister sites in the Sacramento Valley (Bugg, pers. obs.).

Days to Maturity

Common annual ryegrass flowers from June through August (Munz, 1973) and matures seed by mid June (Finch and Sharp, 1983). 'Wimmera 62' matures in late May (Finch and Sharp, 1983), about 2 weeks earlier than common ryegrass (Finch and Sharp, 1983; Slayback, pers. comm.).

Seed Production

1,484 kg/ha was the average yield in the U.S.A. during 1981 (Riewe and Mondart, 1985). Heavy seed yields are obtained on favorable sites with high soil fertility (USDA-SCS, 1973).

Seed Storage

Stored seed remains viable for a relatively long time (McLeod, 1982).

Growth Habit

Growth habit is erect and robust with vigorous leafy growth (USDA-SCS, 1973; Finch & Sharp, 1983). The plant grows rapidly, providing quick cover (McLeod, 1982). 'Wimmera 62' has an upright growth habit (Finch and Sharp, 1983).

Maximum Height

Grows to about 4 feet height in the most favorable environments (USDA-SCS, 1973), whereas Miller (1984) indicated height of about 130 cm (52 in). Measurements by Bugg et al. (unpublished data) in a replicated study (r=4) at the Blue Heron Vineyard (Fetzer Vineyards), Hopland, Mendocino County, California, May 2, 1991, showed that height for annual ryegrass (cv 'Oregon Common') was 92.08+/-4.20 cm (Mean +/- S.E.M.).

Root System

Like most grasses, annual ryegrass has a fibrous root system (Finch & Sharp, 1983), which can be extensive (Peaceful Valley, 1988). Finch and Sharp (1983) mention that 'Wimmera 62' has "heavy roots."

From data presented by Jackson et al. (1993b), for mid-November-planted cover crops in March, approximate values for N contained in root systems obtained by subtraction were as follows in kg N/ha:

Annual ryegrass:	20
White mustard:		35
Oilseed radish:		58
Phacelia:		57
Merced cereal rye:	19
White senf mustard:	13

Jackson et al. (1993b) stated that, for mid-November-planted cover crops in March, root biomass figures in kg/ha were:

Annual ryegrass:	883
White mustard:		2,273
Oilseed radish:		4,128
Phacelia:		1,502
Merced cereal rye:	950
White senf mustard:	592
Standard error: 	680.8 (d.f.=10)

Jackson et al. (1993b) stated that, for mid-November-planted cover crops in March, root length measurements yielded the following figures during March (m/m2):

Annual ryegrass:	20,700
White mustard:		22,200
Oilseed radish:		15,300
Phacelia:		19,800
Merced cereal rye:	19600
White senf mustard:	13,100
Standard error 		(d.f.=10)=2,818.8

Kutschera (1960) reported that annual ryegrass generally roots to a depth of 86-135 cm.

Establishment

Annual ryegrass seed germinates quickly (McLeod, 1982; Peaceful Valley, 1988), and the species is known for rapid growth (McLeod, 1982) and ease of establishment even during cold weather (Miller et al., 1989). Perennial ryegrass has slower seedling establishment and lower seedling vigor than does annual ryegrass (Miller, 1984).

Maintenance

Annual ryegrass can persist almost indefinitely in pastures, orchards, vineyards, wildlife areas and critical areas if permitted to set and drop seed. When used for temporary cover, annual ryegrass should be kept from setting seed by plowing under, disking, or mowing during early bloom (USDA-SCS, 1973). Annual ryegrass shows excellent performance and reestablishment in mature pecan orchards of southern Georgia where there is little shade from late November until mid-April (Bugg, R.L., pers. comm.). Reestablishment has also been excellent in vineyards in sites as diverse as Ukiah (Mendocino Co.) and Porterville (Tulare Co.). Reseeding by 'Wimmera 62' may not be as consistent as other ryegrasses. A three to four week growing period (without mowing) must be provided prior to the late May maturity to allow seed to be produced (Finch and Sharp, 1983).

Mowing

Mow temporary lawns of ryegrass no closer than three inches. When ryegrass is used for over-seeding bermuda, the mower should be lowered to one inch cutting height in the spring to kill the ryegrass and leave a clean stand of bermuda. Ryegrass should be cut no later than early bloom for high quality hay. Strips of uncut forage should be left to produce seed if another hay crop is to be taken the following year (USDA-SCS, 1973). Both annual and perennial ryegrasses should be cut no closer to the ground than about 7.5 cm (3 in) (Miller, 1984). 'Wimmera 62' can be mowed frequently during the growing season above 2 inches. A three to four week growing period must be provided prior to the late May maturity date to allow seed to be produced (Finch and Sharp, 1983).

Incorporation

Can be disked down in the spring (Finch & Sharp, 1983). When used for temporary cover, annual ryegrass should be kept from setting seed by plowing under, disking, or mowing during early bloom (USDA-SCS, 1973).

Harvesting

To harvest seed, cut annual ryegrass when one or two florets dislodge from most heads as heads are pulled lightly through the fingers. Windrow and allow to dry for several days prior to threshing. Dry seed to 12% moisture prior to threshing (Riewe et al., 1985).

Equipment

Annual ryegrass can be mowed or incorporated like any annual cover crop, and has no special equipment needs (Bugg, pers. comm.).

Uses

Lolium multiflorum can be spring- or fall-grazed, hayed, used as cover crop, plowed as green manure, or used as nurse crop for fall-seeded legumes (McLeod, 1982; Miller, 1984; Hofstetter, 1988). Its rapid growth and the quick cover it affords make it excellent for temporary pasture (McLeod, 1982). In California, it is often used in preparation for crops that must be planted in the spring, and it can often be grown where other cover crops have not proved satisfactory (Miller et al., 1989). Its uses include: (1) fall over-seeding of bermudagrass turf; (2) pasture, hay, wildlife habitat; (3) temporary cover for lawns, critical areas, and burned areas; and (4) winter green manure and cover crops for orchards and cropland. It is a good choice for obtaining fast temporary cover on exposed areas with minimal seedbed preparation (USDA-SCS, 1973).

Annual ryegrass shows excellent performance in mature pecan orchards, which have little shade from late November until mid- April (Bugg, R.L, pers. comm.). Reestablishment has also been excellent in vineyards in sites as diverse as Ukiah (Mendocino Co.) and Porterville (Tulare Co.). Annual ryegrass has very vigorous seedlings, and provides rapid ground cover. It can be used as a cover crop in grass waterways or flood canals, or on cropland subject to flooding (Miller, 1984). 'Wimmera 62' can be used in similar sites as other reseeding annuals, if its high biomass production is not troublesome (Finch and Sharp, 1983).

Raderschall and Gebhardt (1990) grew three winter crops (barley, rapeseed, and Italian [annual] ryegrass) following faba bean (cv 'Alfred') in order to evaluate their abilities to accumulate residual nitrogen. Accumulation of nitrogen was as follows (kg/ha): barley ('Cosina') - 36.2, rapeseed (cv 'Buko') - 52.1, and Italian [annual] ryegrass of Welsh origin (cv 'Deltex') - 22.9. Carbon/Nitrogen ratios were: barley - 20.3, rapeseed - 22.0, and Italian [annual] ryegrass - 31.0. Dry matter (biomass) accumulation was (tons/ha): barley - 17.2, rapeseed - 25.4, and Italian [annual] ryegrass - 14.8. Rapeseed was superior in retaining nitrogen that might otherwise be leached as nitrate. However, the residues of Brassicaceae such as rapeseed tend to break down and re-release N quicker than do those of grasses (Poaceae).

Mixtures

This species has been recommend for planting with annual legumes to promote nitrogen fixation by the latter and for improved palatability of the resulting hay or pasture (Peaceful Valley, 1988). Graves et al. (1987) planted 'Multicut' berseem and annual ryegrass in mixtures in field trials at Davis (Yolo County, California). Annual ryegrass alone yielded about half as much biomass as 'Multicut' alone. The mixtures of 50% and 75% 'Multicut' with ryegrass yielded as much as 'Multicut' alone (13,800 lbs/acre dry matter). 'Multicut' became dominant in all mixtures by the third harvest. Mixtures of 'Multicut' berseem clover and annual ryegrass combine advantages of both plant species by providing early winter production as well as extending the availability of high quality forage through late spring (Graves et al. 1989).

Annual ryegrass is often grown in conjunction with crimson, alsike, or arrowleaf clovers (Miller, 1984). Adequate phosphorus and potassium are critical when annual ryegrass is grown with a legume (Riewe and Mondart, 1985). When seeded along with legumes (e.g., annual reseeding species) or some other grasses (e.g., perennial ryegrass), annual and perennial ryegrasses contribute to better control of weeds (Miller, 1984). In such situations, the annual ryegrass establishes first and suppresses weeds (Riewe and Mondart, 1985). Both annual and perennial ryegrasses can be sown along with small grains, such as cereal rye and to some extent oat. Oat does not complement ryegrasses as well, because forage is produced at the same time (Miller, 1984). Both annual and perennial ryegrasses can be seeded into bermuda grass sod (Miller, 1984).

Both annual and perennial ryegrasses should be sown at 20-28 kg/ha (18- 25 lb/a) for pure stands, and 11-17 kg/ha (10-15 lb/a) if sown along with a legume or a small grain (Miller, 1984).

Crimson clover can be grown in conjunction with rye, vetches, annual ryegrass, and various cereals. When sown in combination with companion crops, crimson clover is usually sown at 2/3 the normal rate and the other crop at 1/3 the monocultural rate. Developmental rates of annual ryegrass and tall fescue are similar to that of crimson clover (Knight, 1985).

Biomass

For cv 'Aubade', the three-year average yield during clipping experiments at Tifton, Georgia, in dry forage was 4663 lbs/acre (Morey and Marchant, 1977). Hofstetter (1988) reported that early seeded in September and cut in second week of May yielded 1,736 lb/acre of dry matter. Slayback (Cantisano, pers. comm.) considered annual ryegrass a heavy producer given good soil fertility but that the species could present unspecified management problems. About three tons of hay per acre per year can be produced on fertile soils with adequate moisture up to crop harvest (USDA-SCS, 1973). Annual ryegrass averaged 6,800 lbs/acre dry matter production over four years of field testing under supplemental irrigation in the Central Valley (Morey and Marchant, 1977). Williams et al. (1990) obtained 6,800-8,800 lb/ac in four-year study on an irrigated Yolo loam at UC Davis. Bugg et al. (1996) measured total above-ground dry biomass of annual ryegrass called "Oregon Common" in a replicated trial (r=4) at the Blue Heron Vineyard (Fetzer Vineyards), Hopland, Mendocino County, California, May, 1991: 8.5 +/- 3.3 Mg/ha (Mean +/- S.E.M.). With weeds included, the corresponding figure was 10.9+/-1.6 Mg/ha.

Morey and Marchant (1977) reported an 8-year average for common annual ryegrass of 5,286 lbs dry forage/acre, and a three-year average yield during clipping experiments at Tifton, Georgia, as being 4820 lbs dry forage/acre. For cv 'Gulf' the corresponding three-year average was 5611 and was 5423 for 'Magnolia' (Morey and Marchant, 1977). Raderschall and Gebhardt (1990) reported that Italian [annual] ryegrass (cv 'Deltex') yielded 14.8 Mg dry matter/ha.

Miller et al. (1994) exposed residues of annual ryegrass, red clover, and oilseed radish [Raphanus satinus L. var. oleifera (DC) Metzg.] to simulated rainfall. They found that the potential P concentrations in run-off (mg/l) would be in the range of 1-3 for red clover, 4-11 for ryegrass, and 7-16 for oilseed radish. The presence of a cover crop increases the potential P concentration in run-off more than manure without incorporation. However, this potential will seldom be achieved because cover crops reduce erosion and run-off by several mechanisms.

According to Prine (1991), three- to five-year seasonal means of annual ryegrass biomass production (kg/ha) were: Surrey: 6830; Flonicla 80: 6580; Gulf: 6420; Marshall: 6540; NK Tetrablend 444: 6310 (4 years); Magnolia: 5250 (3 years); Rustmaster: 5860 (3 years).

Jackson et al. (1993b) stated that, for mid-November-planted cover crops in March, above-ground biomass figures in kg/ha were:

Annual ryegrass:	2,070
White mustard:		5,913
Oilseed radish:		4,128
Phacelia:		4,552
Merced cereal rye:	4,410
White senf mustard:	5,893
Standard error 		(d.f.=10)=201.3

N Contribution

Annual ryegrasses do not fix atmospheric N, but have been used as catch crops to reduce leaching loss of nitrate through the soil profile. N content of annual ryegrass was presented as 1.37%, and total N as 24 lb/acre by Hofstetter (1988). For Williams et al. (1990), the corresponding figures were 2.1 to 2.4% and 145 to 210 lb N/ac, with uptake of soil N ranging from 50-235 kg N/a, based on a four-year study on an irrigated Yolo loam at UC Davis.

Theiss (1990) indicated that perennial ryegrass does not appear as efficient at N uptake as are annual ryegrass and cocksfoot (Dactylis glomerata) after high initial rates of N fertilization. However, the release of nitrogen from perennial ryegrass swards apparently takes place later in the autumn than for the other two grasses. Thick stands of grasses (perennial ryegrass, annual ryegrass and cocksfoot [Dactylis glomerata]) are more effective at N uptake than are open stands. Drought stress reduced N uptake by annual ryegrass more than by perennial ryegrass or cocksfoot. Over a 9-month period, a catch crop of annual ryegrass between crops of winter wheat and corn (maize) reduced leaching of fertilizer-derived N from 18.7 to 7.1% of the total N applied (200 kg N/ha) (Theiss, 1990). However, there was some suppression of the following maize crop after the ryegrass was plowed under (Martinez and Guiraud, 1990).

In a lysimeter study, Guiraud et al. (1990) found that a catch crop of annual ryegrass reduced the total amount of nitrate N leached from 124 kg N/ha to 40 kg N/ha. The percentages of fertilizer nitrogen in the water were 19% under bare fallow and 7% under the catch crop. To a depth of 30 cm, 23% of labeled N was retained in organic form where ryegrass had been incorporated, versus 15% under bare fallow.

Foliage of annual ryegrass can accumulate 7 or 30 kg of atmospheric ammonia nitrogen/ha during 6 weeks of the growing period (at the atmospheric concentrations of 6 or 89 micrograms of ammonia nitrogen per cubic meter) (Sommer and Jensen, 1991).

In replicated studies in Salinas, CA, Jackson et al. (1993b) reported that November-planted cover crops had attained the following total-plant N content (kg N/ha) figures by March; approximate above-ground N contents were read from a graph and are given parenthetically:

Annual ryegrass:	85 (65)
White mustard:		205 (170)
Oilseed radish:		200 (142)
Phacelia:		182 (125)
Merced cereal rye:	129 (110)
White senf mustard:	161 (148)
Standard error: 	20.2, d.f.=10

From data presented by Jackson et al. (1993b), for mid-November-planted cover crops in March, approximate values for N contained in root systems obtained by subtraction were as follows in kg N/ha:

Annual ryegrass:	20
White mustard:		35
Oilseed radish:		58
Phacelia:		57
Merced cereal rye:	19
White senf mustard:	13

Non-N Nutrient Contribution

Annual ryegrass hay typically contains an amount of P equivalent to 13 lbs P2O5/ton, an amount of K equivalent to 37 lbs K2O/ton, and has a C/N ratio of 24 (Parnes, 1990).

Effects on Water

A cover crop of annual ryegrass can increase infiltration by irrigation water, though not as much as cereal rye or barley (Williams, 1966), and the species has therefore been suggested for vineyards (Christensen et al., 1968)

Raderschall and Gebhardt (1990) grew three winter crops (barley, rapeseed, and Italian [annual] ryegrass) following faba bean (cv 'Alfred') in order to evaluate their abilities to accumulate residual nitrogen. Accumulation of nitrogen was as follows (kg/ha): barley ('Cosina'): 36.2, rapeseed (cv 'Buko'): 52.1, and Italian [annual] ryegrass of Welsh origin (cv 'Deltex'): 22.9. Carbon/Nitrogen ratios were: barley - 20.3, rapeseed - 22.0, and Italian [annual] ryegrass - 31.0. Dry matter (biomass) accumulation was (tons/ha): barley - 17.2, rapeseed - 25.4, and Italian [annual] ryegrass - 14.8. Rapeseed was superior in retaining nitrogen that might otherwise be leached as nitrate. However, the residues of Brassicaceae such as rapeseed tend to break down and re-release N quicker than do those of grasses (Poaceae).

Effects on Microclimate

No specific information was available on the effects of microclimate by annual ryegrass. Annual ryegrass stays green later than most varieties of barley, oat, or rye, and hence might be expected to transpire more and have a greater cooling effect during late spring in orchards or vineyards (Bugg, pers. comm.).

Effects on Soil

This species has a heavy, extensive, fibrous root system that holds the soil well and opens it to increased infiltration by water; the vigorous seedlings provide rapid ground cover (McLeod, 1982; Peaceful Valley, 1988).

A cover crop of annual ryegrass can increase infiltration by irrigation water (Williams, 1966), and the species has therefore been suggested for vineyards (Christensen et al., 1968)

Annual ryegrasses do not fix atmospheric N but have been used as catch crops to reduce leaching loss of nitrate through the soil profile. N content of annual ryegrass was presented as 1.37%, and total N as 24 lb/acre by Hofstetter (1988). For Williams et al. (1990), the corresponding figures were 2.1 to 2.4% and 145 to 210 lb N/ac, with uptake of soil N ranging from 50-235 kg N/a, based on a four-year study on an irrigated Yolo loam at UC Davis.

Raderschall and Gebhardt (1990) grew three winter crops (barley, rapeseed, and Italian [annual] ryegrass) following faba bean (cv 'Alfred') in order to evaluate their abilities to accumulate residual nitrogen. Accumulation of nitrogen was as follows (kg/ha): barley ('Cosina') - 36.2, rapeseed (cv 'Buko') - 52.1, and Italian [annual] ryegrass of Welsh origin (cv 'Deltex') - 22.9. Carbon/Nitrogen ratios were: barley - 20.3, rapeseed - 22.0, and Italian [annual] ryegrass - 31.0. Dry matter (biomass) accumulation was (tons/ha): barley - 17.2, rapeseed - 25.4, and Italian [annual] ryegrass- 14.8. Rapeseed was superior in retaining nitrogen that might otherwise be leached as nitrate. However, the residues of Brassicaceae such as rapeseed tend to break down and re-release N quicker than do those of grasses (Poaceae).

Effects on Livestock

Both annual and perennial ryegrasses can be sown along with small grains, such as cereal rye and to some extent oat. Oat does not complement ryegrasses as well because forage is produced at the same time. Ryegrasses may equal small grains in forage quality and exceed them in production. When sown in mixtures with small grains, ryegrasses extend the spring grazing season (Miller, 1984).

Annual ryegrass has excellent palatability to livestock.

Effects on Workers

Some agricultural workers may be allergic to the wind-blown pollen of annual ryegrass (Slayback, pers. comm.).

Pest Effects, Insects

In a trial comparing insect densities under 17 cover-cropping regimes in southern Georgia, annual ryegrass (Lolium multiflorum cv 'Gulf') harbored few aphids and virtually no associated beneficial insects (e.g., lady beetles [Coccinellidae]). Comparisons of monocultural and bicultural plots showed that interspersion of ryegrass with hairy vetch and crimson clover caused an overall reduction in aphid and coccinellid densities on these legumes, but differences were not consistent through time (Bugg et al., 1990).

In southern Oregon pear orchards, some species of understory weeds can harbor high densities of twospotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae). This mite is mainly a secondary pest and a creature of pesticide-disrupted or stressed agroecosystems. Among the plant species suitable for use as cover crops, ryegrass appeared of intermediate favorable as host of the mite (Flexner et al., 1990).

Pest Effects, Nematodes

Annual ryegrass is a host of Bromegrass Mosaic Virus which is transmitted by 2 plant-parasitic nematodes (Xiphinema spp.) (Slykhuis, 1967). Townshend and Davidson (1989) evaluated thirty-five wild and cultivated grasses and 4 forage legumes in small plots and determined that annual ryegrass harbored especially high densities of pin nematode (Paratylenchus projectus). On the other hand, the species harbored particularly low densities of root lesion nematode (Pratylynchus penetrans) in an orchard in Ontario, Canada (Marks and Townsend, 1973).

Pest Effects, Diseases

This species is a host of Bromegrass Mosaic Virus which is transmitted by 2 plant-parasitic nematodes (Xiphinema spp.) (Finch and Sharp, 1983).

Resistance to crown rust (Puccinia coronata) varies among annual ryegrass cultivars, with 'Florida 80,' and 'Surrey' performing best (Prine, 1991).

Pest Effects, Weeds

This species is very vigorous and competes well against most weeds (USDA-SCS, 1973; Peaceful Valley, 1988). When seeded along with legumes or some other grasses, annual and perennial ryegrasses contribute to better control of weeds (Miller, 1984). In Hopland, Mendocino County, California, weed above-groundbiomass (dry) in plots sown during late October with annual ryegrass ('Oregon Common') was 2.5+/-2.5 Mg/ha, Mean +/- S.E.M. (Bugg et al., 1996), which was 50.4% of the weed biomass obtained in unseeded control plots. Dominant winter annual weeds were chickweed, shepherds purse, rattail fescue, and annual ryegrass. Vegetational cover data by the sown annual ryegrass in May, 1991 was rated as 100.0+/-0.0 % (Mean +/- S.E.M.).

Annual ryegrass is itself a weed in some orchard, vineyard, and restoration-ecology settings. It is difficult to remove by mowing because of its ability to produce horizontal culms.

Pest Effects, Vertebrates

No information was available on the vertebrate pest effects of annual ryegrass; in general, annual grasses do not support as many gophers as do perennial legumes (Bugg, pers. comm.).

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