Alfalfa
(family: Fabaceae, the pea family) is a genus of perennial
flowering plant,
Medicago, most commonly referring to M. sativa L., also called lucerne. Alfalfa
is a perennial plant, living from
five to twelve years, depending on variety and climate. It is a cool season perennial
legume, 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 being found worldwide and
most likely originated in the middle east, probably in Iran. It is widely grown
throughout the world as forage for cattle most often harvested as
hay having the highest feeding
value of all common hay crops, being used less frequently as pasture or haylage.
Like other legumes, it has 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 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 United States and Australia. 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.
Alfalfa is believed to be a galactagogue. A
few other species of Medicago are called alfalfa; others are called medick,
barrelclover, or burclover. CultureAlfalfa
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 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. In most
climates, alfalfa is cut three or four times a year. Total yields are typically
around 1 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 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. VarietiesConsiderable
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. External
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