Alfalfa

Alfalfa is a perennial plant, living from five to twelve years, depending on variety and climate. Growing to a height of 1 metre, it resembles clover with clusters of small purple flowers. It also has a deep root system sometimes stretching to 4.5 meters. This makes it very resilient, especially to droughts.

Alfalfa is native to Europe and it widely grown throughout the world as forage for cattle. Like other legumes, it has the ability to fix nitrogen, producing a high-protein feed regardless of available soil nitrogen. It is most often harvested as hay, less frequently as pasture or haylage.

Its wide cultivation beginning in the seventeenth century was an important advance in European agriculture. Its nitrogen-fixing ability 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 plowed down or rotated before reseeding.

Alfalfa sprouts are used as salad ingredient in the US and Australia. The leading Alfalfa growing states are Wisconsin and California.

A few other species of Medicago are called alfalfa; others are called medick, barrelclover, or burclover.

Culture

Alfalfa can be sown spring or fall, and does best on well-drained soils with a neutral pH (6.8-7.5). Alfalfa requires a great deal of potash; soils low in fertility should be fertilzed with manure or a chemical fertilizer. Usually a seeding rate of 15 pounds per acre is used. A nurse crop is often used, particularly for spring plantings, to reduce weed problems. Herbicides are sometimes used instead.

In most climates, alfalfa is cut three or four times a year. Total yields are typically around 4 tons per acre but vary regionally and with weather, and with stage of maturity when cut. Later cuttings improve yield but reduce nutritional content.

The alfalfa leafhopper can reduce 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. The pollinator of choice are the ground nesting alfalfa leafcutter bee, which is cultured in special beds near the seed fields, or honeybees which are trucked to the fields when needed.

Varieties

Considerable research and development has been done with this important plant. The "Vernal" variety was introduced c. 1970 and was the standard for years to come. Many better public and private varieties are available now, and are adapted to the needs of particular climates.

Most of the improvements in alfalfa over the last decades have been in disease resistance, improved ability to overwinter in cold climates, and multileaf traits. Disease resistance is important because it improves the usefulness of alfalfa on poorly drained soils, and during wet years.

Multileaf alfalfa has more than three leaflets per leaf. It has a higher nutitional content by weight because there is relatively more leafy matter for the same amount of stem.

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