OREGON STATE UNIVERSITY
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Rye has been cultivated for more than 2,000 years. It was the predominant world grain for making bread until the 19th century when it was replaced with wheat. Although cereal rye is planted primarily for grain, it is also a valuable forage (for spring pasture, hay, or silage) and as a winter cover crop.
Rye is a tufted annual or biennial grass reaching up to 5 feet (1.5 m). It is the tallest and most winter hardy annual cereal crop. Rye has an extensive, fibrous root system. When it is used as a cover/forage crop in double cropping systems (a warm season crop followed by fall planting of rye), harvesting rye for forage during spring provides early, supplementary forage and/or income when sold as hay or silage.
Rye can survive harsh winters and is tolerant of adverse soil conditions, including sandy soils with low fertility and drought conditions. It has very good tolerance to low pH and aluminum toxicity, so is better adapted to highly acidic soils than other cereals. It requires about 30 percent less water than wheat. In some cases, the production of rye offers the only chance of economic returns on marginal land. There are both winter and spring types of rye. Winter types are more common.
Rye has a bunch-grass habit. It is an annual plant.
The SARE Outreach article on Cereal Rye (https://www.sare.org/publications/managing-cover-crops-profitably/nonlegume-cover-crops/cereal-rye/) provided a generalized US map showing suitability zones for cereal rye. It shows that rye is suitable to almost all parts of the US, except for far southern regions of CA, AZ, TX, and FL. However, this map is not able to distinguish conditions of sensitivity or potential yield.
To create greater ability to accurately match appropriate rye production areas to climate and soil conditions, GIS-based suitability maps were developed for the USA and Oregon based on quantitative tolerances to climate and soil factors. Quantitative functions were developed in R-Studio for each factor and parameters estimated for ArcGIS mapping.
Temperature: As the most winter-hardy of all cereal grains, rye tolerates temperatures as low as -30°F (-34 °C) once it is well established. It can germinate and grow at temperatures as low as 34°F (1 °C) and initiate vegetative growth at 38 °F (3.3 °C), with an optimum growth temperature of 64.4 °F (18 °C).
Typically seeded from late summer to mid-autumn in USDA Plant Hardiness Zones 3 to 7 and from fall to mid-winter in Zones 8 and warmer.
Annual precipitation: Cereal rye can be grown in areas with as little as 450 mm (18 in) of annual precipitation.
Its extensive root system enables it to be the most drought-tolerant cereal crop; it is more drought tolerant than oat and requires 20-30% less water than wheat per unit of dry matter.
pH: Tolerant of strongly acid to moderately alkaline soils (5.1-8.4).
Aluminum: Somewhat tolerant of aluminum (persisted at 1–2 ppm Al3+ and pH 4.0).
Soil drainage: Suited to well-drained and moderately well-drained soils (WD-MWD).
Flooding: Tolerant of brief flooding only (3-6 days).
Salinity: Higher tolerance of salinity than other cereals, 6-12 dS/m (millimhos/cm).
Global and USA Suitability
The United States is a significant producer of rye. In 2020 the U.S. produced roughly 11.5 million bushels of rye that was valued at approximately $59.8 million. The marketing year average price for rye was $5.20 per bushel. In 2022, 12.3 million bushels of rye were produced, an increase of about 9.8 million bushels from the 2021 total production. The national average yield for rye is around 35 bu per acre.
Winter rye is commonly planted as a cover crop. As an example, in 2021, of the 2.1 million acres planted only 294,000 acres were harvested for grain. Therefore, a significant market for rye can be for seed that will be planted as a cover crop. The states with the most harvested acres of rye are Oklahoma, North Dakota, Minnesota, Pennsylvania, and Wisconsin.
Suitability Zones
GIS-based suitability zones were divided into four suitability zones, based on their climatic and edaphic tolerances. An arbitrary classification system based on 25% differences in relative yield (RY) was used: (1) 75-100% RY = well-suited; (2) 50-75% RY = moderately-suited; (3) 25-50% RY = marginally-suited; and (4) 0-25% RY = not suited.
Rye is a cool-season grass with optimum growth rates between 64 and 68 ̊F (18-20 ̊C).
Winter rye can be planted early into cool soils [~40 ̊F (4.4 ̊C)] and can be harvested for forage in 58-65 days. The sigmoidal growth curve of plant height vs days after planting of rye is illustrated in a Kansas State University publication: http://courses.missouristate.edu/WestonWalker/AGA375_Forages/Forage%20Mgmt/References/2Forages/4Annual/2Cool
Winter rye is planted in late summer or early autumn, growing sufficiently for light grazing before growth stops due to low temperatures. Spring harvest at the soft-dough to dough stage is early enough to allow a double-cropping system with corn, sorghum, or other warm-season annual grasses.
Irrigation Requirements
Adequate soil moisture during germination and early seedling growth is important for cool-season annuals planted for forage. When managed as a grazing or hay crop, emphasis should be focused on meeting the plant’s water needs during rapid growth stages (see Figure 7 of this web link: https://extensionpublications.unl.edu/assets/html/g2012/build/g2012.htm).
Even moderate water stress during vegetative stages is likely to reduce yield, although it may lead to improved forage quality.
Note: Irrigation needs during August and early September can be relatively high, reducing water-use efficiency, especially when compared to spring-planted systems.
Cultivar Types
Currently, most cereal rye seed planted as forage or cover crop are: “variety not stated” (VNS). However, there are cultivar evaluation trials conducted at numerous land grant universities that can help guide selection.
Although cereal rye is usually regarded as a fall-planted winter annual crop, spring sowing is also possible. Drought tolerance among cultivars varies, with diploids more tolerant than tetraploids.
Rye harvested at boot stage typically produces 2 to 3 tons of dry matter per acre (4.48-6.72 MT/ha) with quality levels acceptable for many animal production groups. The nutritional content of cereal rye forage varies widely depending upon the maturity of the forage; vegetative stage rye can have a crude protein content exceeding 20% and a TDN of 70%, whereas boot to full-heading harvested forage can vary from 13 to 7% CP and 63 to 53% TDN, and straw may be only 4% CP and 44% TDN.
“Ergot (Claviceps purpurea) disease and ergot poisoning” is often a hazard associated with rye. Ergotism is the result of long-term ergot poisoning, traditionally due to the ingestion of the alkaloids produced by the fungus that infects rye and other cereals. Dark-purple or black grain kernels, known as ergot bodies, can be identifiable in the heads of cereals just before grain harvest. Grazing vegetative rye or harvesting for silage or hay in the boot stage prevents the development of the ergot bodies.
See descriptions for nitrate poisoning, grass tetany, and bloat provided in the “Growing Small Grain Cereals for Forage” document.
