OREGON STATE UNIVERSITY
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Perennial, cool-season bunchgrass used commonly as a forage. Closely resembles annual ryegrass but can be distinguished by an abundance of lower leaves and awnless lemmas. Reaches height of 1-2 feet at maturity. Performs well in moist, cool regions with mild winters. Does well in pure stands and in mixtures with legumes or certain other grasses such as orchardgrass and tall fescue.
Habit: Bunchgrass
Temperature: 68°F to 77°F. Sharp decline in production after 87°F.
Precipitation: Minimum of 18-25 inches, with 40-60 inches ideal.
pH: 5.1-8.4, optimal conditions are 6-7.
Salinity: Moderately tolerant (3-6 dS/M)
Soil Drainage: Well drained to Poorly drained (WD-PD)
Drought Tolerance: Low
Climate suitability characteristics in the following table are based on field experiments and forage agronomist experience. Soil factor data are based on values provided in Chapter 3 of the NRCS Range and Pasture Handbook (https://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/stelprdb1043060.pdf).
Climatic and soil factor values for well-suited, moderately-suited, and marginally suited classifications.
| July Max Temp (°C) | January Min Temp (°C) | Annual Precipitation (mm) | Soil pH | Soil Drainage Class | Soil Salinity (dS/m) | |
| Well-suited | 30 | -10 | 600 | 5.75-7.5 | MWD | 2 |
| Moderately-suited | 32 | -15 | 500 | 5.5-7.75 | SPD-MWD | 8 |
| Marginally-suited | 34 | -20 | 400 | 5.25-8.0 | WD | 8 |
Response functions were developed from these tabular values using Rstudio scripts, with parameters provided for climatic and soil GIS spatial data layers.
Suitability patterns for forage species are caused by different factors in different locations. Low winter temperatures limit the northern range of many species, while low precipitation limits the western range of species in the semi-arid west. Low summer temperatures limit the range of species with increasing elevation while high summer temperatures limit the range in the desert southwest and hot and humid southeast. Soil characteristics (pH, drainage, and salinity) also limit the suitability zones of forage species. However, soil amendments (liming and drainage tiles) can alleviate many of these limitations. Thus, NRCS Soil Survey data should be informed and revised by management mitigations.
Nine maps have been developed; 1) 30-year long-term July maximum temperature 2), 3) 30-year long-term annual precipitation, 4) soil pH, 5) soil drainage, 6) soil salinity, 7) combined climate factors, 8) combined soil factors, and 9) combined climate and soil factors.
Performs best in moist, cool conditions without harsh winters. Annual yield may reach 2-4 tons dry matter/acre under optimal conditions and proper management. Season of greatest production is mid-May through June.
Perennial ryegrass easily cross pollinates with other species but does not self-pollinate, leading to many varieties developing. Difficulties keeping genetic purity due to propensity for cross pollinating.
Tetraploid varieties stand more upright and are utilized more often as a forage. Diploid varieties are more persistent under grazing and used more often for pasture.
