OREGON STATE UNIVERSITY
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Alfalfa is a palatable and productive herbaceous perennial legume with worldwide distribution. It is grown in every state of the US. Hundreds of cultivars have been developed. Growth habit is upright, with crowns having 5-25 stems growing 23-35 inches (60-90 cm) in height. Regrowth occurs from crown buds or axillary stem buds. Alfalfa has a prominent taproot. However, typically 60-70 percent of the root system is concentrated in the upper 6 inches (15 cm) of soil, with fibrous roots predominating and bearing most of the nitrogen fixing nodules. It is high yielding and high in quality, but requires high fertility and large quantities of water for optimum productivity. It is grown primarily for hay, but can be ensiled or used as pasture, either alone or in combination with grasses (typically orchardgrass or smooth bromegrass). Dehydrated alfalfa can be pelleted, cubed, or sold as meal.
Growth habit is upright from a crown with 5-25 stems. Regrowth initiates from crown buds or axillary stem buds. Periodic defoliation (28-35 day schedule) is required to restore root carbohydrates for long stand life. Longevity is typically 3-6 years, depending on the cropping system.
Tolerant of drought, heat, and cold. Specific heat and cold tolerances depend on FD and WSI group. [USDA Plant Hardiness zone 3 for most cold-tolerant types; Jan mean minimum of -40 °F (-40 °C); American Horticultural Society Heat Zones 1-9 <150 days above 86 ˚F (30 ˚C)]. Requires 25-40 inches (635-1000 mm) of precipitation or irrigation.
Intolerant of wet or waterlogged soils; soil drainage categories excessively drained to moderately well drained. Tolerates slightly acid to moderately alkaline soils (pH 6.1-8.4). Moderately sensitive of saline conditions (1.5-3 dS/m). Intolerant of water-soluble aluminum (persistence reduced at 0.5 ppm Al3+).
Defining the regions within the USA where the various fall dormancy (FD) and winter survival index (WSI) alfalfa cultivar types can be successfully used is an important marketing and management application of GIS technologies. These maps provide a guide for cultivar selection decisions and for identifying areas for conducting further field evaluations to validate and/or revise these maps.
Low winter temperatures limit the northern range of the FD and WSI types, while other climate and soil factors also combine to define optimal cultivar characteristics.
Agronomic field trials have been the standard evaluation technique for selecting cultivars, but extrapolation of information from one site to another for these types of trials has always been problematic. By developing suitability zone maps, based on our best knowledge of cultivar characteristics, field-based evaluation can make more efficient use of available testing resources. Using these techniques and technologies, the limited number of field trials can be extended across the USA and contribute to the global suitability information contained in the quantitative tolerances tables and function.
Drop-down menu for Fall Dormancy Level
Drop-down menu for Winter Survival Index
Climate
Jan Tmin
Jul Tmax
Ann Precipitation
Combined
Soil
pH
Drainage
Salinity
Combined
Climate and Soil Combined
Annual alfalfa forage yield typically ranges from 4 to 10 tons/acre (9,884-24,711 kilograms/hectare). Alfalfa is more tolerant of higher temperatures than other cool-season species. Shoot growth begins at approximately 50 F (10 C), is optimal at 70-75 F (21-24 C), and declines rapidly above 90 F (32 C). Depending on temperature and photoperiod, 3-7 harvests are possible, with typically 22-25 days between harvests.
https://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/nrcs142p2_018586.pdf
Five general types of plant-breeding procedures have been used to develop alfalfa cultivars. These include plant introductions, improved populations, synthetics, hybrids, and strain crosses. Many cultivars have been developed to increase multiple pest resistance, which uses the practice of strain crossing so plant breeders can quickly incorporate multiple resistance traits. There are now hundreds of alfalfa cultivars with 11 fall dormancy (FD), 6 winter survival index (WSI) types, and insect and disease resistance (https://www.alfalfa.org/pdf/2022_Alfalfa_Variety_Leaflet.pdf). This allows for use in cold, temperate regions to subtropical zones.
Alfalfa has the highest feeding value of all commonly grown hay crops when harvested at late bud or early flower stage of maturity, while also being one of the most palatable and nutritious. Alfalfa produces the greatest amount of protein per acre of any livestock feed, and is often used in combination with corn silage in livestock rations to take advantage of the protein and energy content of the two feeds. When cut prior to bloom, it is low in fiber and high in energy. Thus, it is prized as a primary component in dairy cattle rations and is an important feed for horses, beef cattle, sheep, and milking goats.
Bloat often is a problem for animals pastured on alfalfa and various clovers. Bloat is a distention of the rumen caused by an inability of the animal to eructate gases produced in the normal process of fermentation. Unfortunately, the methods of controlling bloat are troublesome, expensive, and only partially effective. Using a grass-legume mixture in pastures, supplementing legumes with grass hays, intensive strip grazing with electric fences, and drylot feeding have all been somewhat successful.
The most effective treatment involves using bloat-preventative materials. These anti-foaming compounds may be added to drinking water, applied as a top-dressing on grain supplements, included in pellets, or added to salt-molasses blocks supplied on pasture. However, the effectiveness of these methods is variable and depends upon animals obtaining a regular supply of bloat preventative.
