Alfalfa (pron.: /?l?f?lf?/; Medicago sativa) is a perennial flowering plant in the pea family Fabaceae cultivated as an important forage crop in the US, Canada, Argentina, France, Australia, the Middle East, South Africa, and many other countries. The English name is adopted from the Spanish, originally alfalfez, which in turn is derived from the Arabic al-fisfisa "fresh fodder". The Spanish name is widely used, particularly in the US but it is also known as lucerne in the UK, Australia, South Africa and New Zealand, erba medica in Italy, meaning medical herb, luzerne in France, and lucerne grass in South Asian English. It superficially resembles clover, with clusters of small purple flowers followed by fruits spiralled in 2 to 3 turns containing 10-20 seeds. Alfalfa has been cultivated by humans since at least the 4th century CE and has some use in herbal medicine. Alfalfa is widely grown throughout the world as forage for cattle, and is most often harvested as hay, but can also be made into silage, grazed, or fed greenchop. Alfalfa usually has the highest feeding value of all common hay crops. It is used less frequently as pasture. When grown on soils where it is well-adapted, alfalfa is often the highest yielding forage plant, but its primary benefit is the combination of high yield per hectare and high nutritional quality. Its primary use is as feed for high producing dairy cowsЧbecause of its high protein content and highly digestible fiberЧand secondarily for beef cattle, horses, sheep, and goats. Humans also eat alfalfa sprouts in salads and sandwiches. Dehydrated alfalfa leaf is commercially available as a dietary supplement in several forms, such as tablets, powders and tea. Alfalfa is believed by some to be a galactagogue, a substance that induces lactation. Alfalfa can cause bloating in livestock, care must be taken with livestock grazing on alfalfa because of its high bloat hazard. Like other legumes, its root nodules contain bacteria, Sinorhizobium meliloti, with the ability to fix nitroge

, producing a high-protein feed regardless of available nitrogen in the soil. Its nitrogen-fixing abilities (which increases soil nitrogen) and its use as an animal feed greatly improve agricultural efficiency. Alfalfa can be sown in spring or fall, and does best on well-drained soils with a neutral pH of 6.8 Ц 7.5. Alfalfa requires sustained levels of potassium and phosphorus to grow well. It is moderately sensitive to salt levels in both the soil and irrigation water, although it continues to be grown in the arid southwestern United States, where salinity is an emerging issue. Soils low in fertility should be fertilized with manure or a chemical fertilizer, but correction of pH is particularly important. Usually a seeding rate of 13 Ц 20 kg/hectare (12 Ц 25 lb/acre) is recommended, with differences based upon region, soil type, and seeding method. A nurse crop is sometimes used, particularly for spring plantings, to reduce weed problems and soil erosion, but can lead to competition for light, water and nutrients. In most climates, alfalfa is cut three to four times a year, but it can be harvested up to 12 times per year in Arizona and southern California. Total yields are typically around 8 tonnes per hectare (4 short tons per acre) in temperate environments, but yields have been recorded up to 20 t/ha (16 short tons per acre). Yields vary with region, weather, and the crop's stage of maturity when cut. Later cuttings improve yield, but with reduced nutritional content. Alfalfa leafcutter bee, Megachile rotundata, a pollinator on alfalfa flower Alfalfa is considered an insectary due to the large number of insects it attracts. Some pests, such as alfalfa weevil, aphids, armyworms, and 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 root rots, including Phytophthora, Rhizoctonia, and Texas root rot.