Alfalfa

Credit: 
Percy Folkard, BC FLNR
Scientific name: 

Medicago sativa L.

Type: 
Agronomic Legume
Annual precip. min (mm): 
300
Annual precip. max (mm): 
600
Seed size: 
Medium
Seeds per kg: 
441,000
Typical seeding objectives: 
PR Suitability note: 
Select varieties that have been tested in the Peace region and are noted for their winter-hardiness. Needs well drained soils where the pH is 5.9 or higher, and prefers soils with pH of 6.2 or higher.
Key considerations: 
Select a non-bloating variety for pasture use if grazing when plants are in the early bud stage. Alfalfa can attract wildlife, and should not be used for roadside seeding where there are wildlife and traffic concerns.
General Description: 

Alfalfa is the most widely used perennial, cool season agronomic legume, and is adapted to many regions and uses. It is palatable for livestock but can cause bloat if not managed carefully.

Alfalfa can have very deep tap roots and a woody crown. There are different types of root systems with different types of alfalfa. The Flemish type has a narrow crown, taproot, and few lateral roots; Siberian has a deep set crown and widely branching roots; variegated types can have roots and crowns like either Flemish or Siberian, or intermediate. Creeping-rooted types have some ability to spread from rhizomes that grow horizontally from primary roots. Shoots may survive as independent plants. Alfalfa crowns are deeper set than most other legumes (except for sweet clover), which increases winter hardiness and survival.

Each alfalfa shoot develops many branches. Flemish types have erect stems and wider leaves, while Siberian types have finer, less upright stems and narrower leaves. Each leaf has three leaflets with finely toothed margins from midway to the point of the leaflet. Multi-foliate types may have more than three leaflets on each leaf.

Flowers form from buds at the base of branches, which continue to grow. Up to twenty flowers are attached to a stalk. Flower colour varies with the type of alfalfa. Flemish: purple; Siberian: yellow; variegated types: purple, blue, green, cream, or yellow. Alfalfa is cross-pollinated and leaf cutter bees are often required to achieve successful pollination. Seeds per pod vary from 3 to 10, depending on the type of alfalfa.

Origin: 
Europe, Middle East, Siberia
Habitat and climate: 
Alfalfa is adapted to a wide range of soils and environments.
Uses: 
Alfalfa is used for hay and pasture, and as stockpiled forage (although quality is limited by frost). It also is used for wildlife habitat and forage and has had some use in post-wildfire and range rehabilitation.
Optimal time of grazing use: 
Cut alfalfa at 10% bloom to optimize both quality and quantity of harvested forage, and to maintain stand productivity. Frequent early cutting will reduce root reserves, potential for growth, and stand longevity. After cutting, alfalfa can be stockpiled for fall grazing after the first killing frost. Grazing can begin at bud stage, but there is a high risk of bloat. Do not graze to less than 10 cm (4 in.) tall. Tolerance to frequent grazing is highly dependent on the variety and health of plant crowns.
Recovery after use (rating): 
M
Recovery after use: 
Allow growth to bud stage before first grazing or regrazing, and allow at least 40 days for plant recovery. Avoid use for 6 weeks before killing frost to reduce winter injury. Alfalfa can be stockpiled for later grazing, but quality declines rapidly.
Forage yield (rating): 
H
Forage yield: 
Provides the highest yield of all agronomic legumes. Yields range from 3,556 kg/ha (3,175 lb/acre) in the Brown soil zone to 6,352 kg/ha (5,671 lb/acre) in the Gray and Black soil zones. Yields can be as high as 7,101 kg/ha (6,340 lb/acre) in the Dark Brown soil zone.
Palatability/Nutritional Value: 
Highly palatable to livestock. Crude protein can be as high as 21% and digestibility is 71%. Can cause bloat with the greatest risk during peak plant growth periods.
Longevity (rating): 
H
Longevity: 
Can live from 3 to 20 years. Creeping rooted alfalfa survives for longer in some regions, whereas taprooted types survive better in northern regions. Longevity affected by management, fertility, timing of grazing by livestock and wildlife, winter hardiness, disease resistance, soil moisture, and pH.
Persistence (rating): 
M
Persistence: 
Persistence is highly variable and very dependent on crown health.
Invasiveness (rating): 
L
Invasiveness: 
Not considered invasive, although it has shown some spread from roadsides into native plant communities in the southern interior.
Competitiveness (rating): 
M
Competitiveness: 
Can be competitive once established, but stand may thin due to winter injury or other stresses, with an increase in grasses or weeds. Creeping rooted alfalfa types are more competitive, and spread by developing new shoots from creeping rootstocks. Established plants with tall stature may cause snow press on tree seedlings if left ungrazed.
Weed resistance (rating): 
L
Erosion control (rating): 
M
Drought tolerance (rating): 
H
Drought tolerance: 
Deep root system allows alfalfa plants to access subsoil moisture more effectively than many other types of forage. It can avoid the effects of drought for up to a year, and will survive longer-term drought by going dormant.
Winter hardiness (rating): 
M
Winter hardiness: 
Difficult to rate hardiness as it is highly variable, dependent on cultivar, type of rooting, snow cover, fall weather conditions, age of stand, nutrient management, type of grazing, and other stresses.
Soil texture preference (rating): 
A
Soil texture preference: 
Prefers well-drained soils of all textures.
Flooding tolerance (rating): 
M
Flooding tolerance: 
Can withstand 1 to 2 weeks of spring flooding and waterlogged soils before spring growth. Waterlogging in fall reduces winter hardiness.
Salinity tolerance (rating): 
M
Salinity tolerance: 
The effects on growth of alfalfa begins at 2 deciSiemen per metre (dS/m). Growth is fair between 4 to 8 dS/m, but there is no growth above 16 dS/m. (Low tolerance would indicate interrupted growth at 4 dS/m or less.)
Acidity tolerance (rating): 
L
Acidity tolerance : 
Tolerates soil pH as low as 6.2.
Fire tolerance (rating): 
L
Pests and/or disease threats: 
Insect pests affecting alfalfa include pea aphid, spotted alfalfa aphid, alfalfa weevil, clover leaf weevil, alfalfa curculio, lygus bugs, alfalfa plant bug, alfalfa seed chalcid, alfalfa looper, alfalfa caterpillar, alfalfa blotch leafminer, alfalfa webworm, leafhoppers, two spotted mite, flower thrips, and grasshoppers. Disease threats include brown root rot, crown rot, winter crown rot, seedling blight, downy mildew, spring black stem, yellow leaf blotch, verticillium wilt, and bacterial wilt.
Ease of establishment (rating): 
H
Ease of establishment: 
Establishes readily, because seedlings emerge early and vigorously to compete with companion crops. Autotoxicity can be a problem between established older alfalfa plants and young seedlings, resulting in stunted plants.
Suggested mixtures: 
Include alfalfa with a grass forage such as crested wheatgrass, meadow bromegrass, timothy, intermediate wheatgrass, smooth bromegrass, and orchardgrass.
Management considerations: 
Inoculate with Rhizobium meliloti before seeding. In acidic soils, root nodulation and nitrogen fixation can be impaired. Responds well to fertilizing with phosphorus and sulfur, and sometimes responds well to micronutrient amendments. Avoid close grazing or cutting during the critical fall period 6 weeks before frost.