Alfalfa, or Lucerne, a plant of the pea family grown primarily for forage, especially as hay. It is one of the most useful and widely grown hay crops in the world. In the United States, more land is used for alfalfa production than for any other hay crop.
Because of its high protein content, alfalfa is used as a food for almost all farm animalsas hay, as silage, or as a temporary pasture crop. Because of its nitrogen-fixing properties, it is used in crop rotation to improve soil for other crops. When planted in combination with grasses, it helps prevent soil erosion. Alfalfa is also grown commercially for seed in arid or semiarid regions. Dehydrated alfalfa is ground into meal and used in feeding poultry and livestock. Indirectly, alfalfa is a source of honey, because bees gather substantial quantities of nectar from alfalfa flowers.
Alfalfa grows from two to three feet (60 to 90 cm) high, depending on soil conditions and water supply. Long taproots (4 to 30 feet [1.2 to 9 m]) draw moisture and nourishment from deep in the subsoil, and enable the plant to grow in dry areas.
A thickened, woody, stemlike structure, the crown, develops at or near the surface of the ground. Some 15 to 50 leafy shoots grow from the crown. The leaves are small, with distinct marginal teeth at the apex. The flowers are predominantly purple, but lavender, cream, yellow, white, and green flowers also occur. The seed pods are twisted and slightly downy, and the seeds are kidney-shaped.Alfalfa is a valuable crop with many slender stems. It is grown mainly for forage.
Alfalfa is grown in almost every state of the United States and, to some extent, in all agricultural areas of the world. Alfalfa grows best in deep, rich, well-drained soil but will adapt to almost any climate and soil. The plant requires considerable amounts of calcium, phosphorus, and potassium. Acid soils must be treated with lime to ensure successful alfalfa growth.
Seeding is accomplished by sowing the seeds with a grain drill (a mechanical device that inserts the seed into the soil) or by scattering the seeds at random and then covering them with soil. The roots of alfalfa plants have small nodules that contain nitrogen-fixing bacteria. These bacteria provide nitrogen necessary for alfalfa growth, and are often added to fields where alfalfa has never been grown. The process of adding these beneficial bacteria to the soil is called inoculation. A field of alfalfa requires very little cultivation, and the crop can be harvested from two to seven times a year.
Damage to alfalfa crops is sometimes caused by field mice, gophers, and ground squirrels. These animals can be controlled by trapping or poisoning. Even greater damage is caused by diseases produced by bacteria and viruses. The most effective, and in many instances the only, method available to combat these diseases is to breed and plant disease-resistant varieties of alfalfa.
Damage to alfalfa crops is also caused by insects (such as the alfalfa webworm, the alfalfa weevil, and the alfalfa aphid). These insects can be controlled by pesticides, by cutting the crop early, and by planting varieties of alfalfa that are resistant to them. Alfalfa is also adversely affected by cold, drought, and humidity.
To maintain the quality of alfalfa, special attention must be paid to the harvesting methods and the weather conditions at the time of harvest. Improper harvesting can result in a loss of some of the carotene (a source of vitamin A for animals) and protein content.
Alfalfa is native to Asia Minor and the Caucasus Mountains, and its use as a cultivated forage plant goes back into antiquity. Alfalfa was grown by the Persians, Greeks, and Romans. Through the ages, its cultivation spread throughout Europe. The Spanish explorers brought alfalfa to Mexico and Chile. The successful planting of alfalfa in the United States began about 1850, when seed was brought to the Pacific coast from Chile by gold prospectors. By 1900 the cultivation of Chilean alfalfa had spread as far east as the valley of the Mississippi River. During the second half of the 19th century another variety of alfalfa was brought to Minnesota from Germany by Wendelin Grimm. Other varieties were developed from the original Chilean and Grimm strains. The Grimm varieties proved to be extremely hardy, and their use spread over the northern states and into Canada.
Many other alfalfa varieties were later introduced into the United States from central Asia. In addition to the Grimm alfalfas and the Chilean varieties, Turkestan alfalfas (from Turkestan in Central Asia), Ladak alfalfas (from northern India), and variegated alfalfas (hybrids formed by breeding common alfalfa with a wild species from Siberia) are among the important varieties planted in the United States.
Most cultivated varieties of alfalfa belong to the species Medicago sativa (called common alfalfa) of the legume family, Leguminosae. The species that grows wild in Siberia is M. falcata.