Alfalfa

Alfalfa (Medicago sativa) is a flowering plant in the pea family Fabaceae cultivated as an important forage crop. In the UK, Australia, South Africa and New Zealand it is known as lucerne and as lucerne grass in south Asia. It resembles clover with clusters of small purple flowers.

Alfalfa is a cool season perennial legume which can live more than twenty years, depending on variety and climate. The plant grows to a height of up to 1 metre (3 ft), and has a deep root system sometimes stretching more than 15 metres (49 ft). This makes it very resilient, especially to droughts. It has a tetraploid genome.

This plant exhibits autotoxicity, which means that it is difficult for alfalfa seed to grow in existing stands of alfalfa. Therefore, it is recommended that alfalfa fields be rotated with other species (for example, corn or wheat) before reseeding.

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 as greenchop. Alfalfa has the highest feeding value of all common hay crops, being used less frequently as pasture. When grown on soils where it is well-adapted, alfalfa is the highest yielding forage plant.

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 sustained levels of potassium and phosphorus to grow well. It is moderately sensitive to salt levels in both the soil and in 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 – 20 kg/hectare (12 – 25 lb/acre) is recommended, with differences based upon region, soil type, and seeding method.[24] 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.

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.[30] Chemical controls are sometimes used to prevent this. Alfalfa is also susceptible to root rots including Phytophthora, Rhizoctonia, and Texas Root Rot.



Source: http://en.wikipedia.org/wiki/Alfalfa



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