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For the Our Gang (Little Rascals) character, see Carl Switzer. For the place, see Alfalfa, Oklahoma. Alfalfa (Medicago sativa), also known as Lucerne, Purple Medick and Trefoil, is a perennial flowering plant cultivated as an important forage crop. Alfalfa lives from five to twelve years, depending on variety and climate. It is a cool season perennial legume, growing to a height of 1 meter. It resembles clover with clusters of small purple flowers. It also has a deep root system sometimes stretching to 4.5 metres. This makes it very resilient, especially to droughts. It has a tetraploid genome. Alfalfa is native to Iran, where it was probably domesticated during the Bronze Age to feed horses being brought from Central Asia. It came to Greece around 490 B.C. being used as a horse feed for Persian army. It was introduced from Chile to the United States around 1860. It is widely grown throughout the world as forage for cattle, and is most often harvested as hay. Alfalfa has the highest feeding value of all common hay crops, being used less frequently as pasture. Like other legumes, its root nodules contain bacteria, like Rhizobium, with the ability to fix nitrogen, producing a high-protein feed regardless of available nitrogen in the soil. Its wide cultivation beginning in the seventeenth century was an important advance in European agriculture. Its symbiotic relationship with nitrogen-fixing bacteria and use as animal feed greatly improved agricultural efficiency. When grown on soils where it is well-adapted, alfalfa is the highest yielding forage plant. Alfalfa is one of the few plants that exhibit autotoxicity. Alfalfa seed will not grow in existing stands of alfalfa because of this. Therefore, alfalfa fields must be cleared or rotated before reseeding. Alfalfa sprouts are used as a salad ingredient in the United States and Australia. Tender shoots are eaten in some places as a leaf vegetable. Human consumption of older plant parts is limited primarily by very high fiber content. Dehydrated alfalfa leaf is commercially available as a dietary supplement in several forms, such as tablets, powders and tea. Alfalfa is believed to be a galactagogue. In the United States, the leading Alfalfa growing states are Wisconsin and California, with most of the latter state's production occurring in the Mojave Desert by means of irrigation provided by the California Aqueduct.
Culture Alfalfa can be sown in spring or fall, and does best on well-drained soils with a neutral pH of 6.8–7.5. Alfalfa requires a great deal of potash. Soils low in fertility should be fertilized with manure or a chemical fertilizer. Usually a seeding rate of 13–17 kg/hectare (12–15 lb/acre) in climatic acceptable regions and a rate of 22 kg/hectare (20 lb/acre) in southern regions is used. A nurse crop is often used, particularly for spring plantings, to reduce weed problems. Herbicides are sometimes used instead. A genetically modified variety which is tolerant to the herbicide Roundup has been developed and will be sold in the United States pending deregulation. In most climates, alfalfa is cut three or four times a year. Total yields are typically around 8 tonne/hectare (4 ton/acre) but vary regionally and with weather, and with stage of maturity when cut. Later cuttings improve yield but reduce nutritional content. The potato leafhopper can reduce alfalfa yields dramatically, particularly with the second cutting when weather is warmest. Chemical controls are sometimes used to prevent this. Alfalfa is also susceptible to Texas Root Rot. Alfalfa seed production requires cultured pollinators to be provided for the fields when in bloom. Alfalfa pollination is somewhat problematic because the keel of the flower trips to help pollen transfer to the foraging bee, striking them in the head. Honeybees apparently do not like being struck, and often learn to defeat this action by drawing nectar from the side of the flower, thus pollination is not accomplished. The majority of the pollination is accomplished by young bees that have not yet learned the trick of robbing the flower without tripping it. When honeybees are used for pollination, the beehives are stocked at a very high rate to maximize the number of young bees. Today the alfalfa leafcutter bee is increasingly used to circumvent this problem. As a solitary but gregarious bee species, it does not build colonies or store honey, but is a very efficient pollinator of alfalfa seed. Nesting is in individual tunnels in wooden or plastic material, supplied by the alfalfa seed growers. A smaller amount of alfalfa seed is pollinated by the alkali bee, mostly in the northwestern USA. It is cultured in special beds near the seed fields. These bees also have their own problems. They are not portable like honeybees; they take several seasons to build up, when fields are planted in new areas. Honeybees are still trucked to many of the fields at bloom time. Harvesting
Varieties
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