Alfalfa

Appearance

The plant superficially resembles clover, especially while young, when trifoliate leaves comprising round leaflets predominate. Later in maturity, leaflets are elongated. It has clusters of small purple flowers followed by fruits spiralled in 2 to 3 turns containing 10–20 seeds. Alfalfa is native to warmer temperate climates. It has been cultivated as livestock fodder since at least the era of the ancient Greeks and Romans.

Naming

The word "alfalfa" is a Spanish modification of the Arabic word "al-faṣfaṣa".

The name alfalfa is used in North America. The name lucerne is more commonly used in the United Kingdom, South Africa, Australia, and New Zealand.

Habitat

Alfalfa is a perennial forage legume which normally lives four to eight years, but can live more than 20 years, depending on variety and climate. The plant grows to a height of up to 1 metre, and has a deep root system, sometimes growing to a depth of more than 15 m to reach groundwater. Typically the root system grows to a depth of 2–3 m depending on subsoil constraints. Owing to this deep root system, it helps to improve soil nitrogen fertility and protect from soil erosion. This depth of root system, and perenniality of crowns that store carbohydrates as an energy reserve, make it very resilient, especially to droughts. Alfalfa has a tetraploid genome.

Alfalfa is a small-seeded crop, and has a slowly growing seedling, but after several months of establishment, forms a tough "crown" at the top of the root system. This crown contains shoot buds that enable alfalfa to regrow many times after being grazed or harvested; however, overgrazing of the buds will reduce the new leaves on offer to the grazing animal.

This plant exhibits autotoxicity, which means it is difficult for alfalfa seed to grow in existing stands of alfalfa. Therefore, alfalfa fields are recommended to be rotated with other species before reseeding. The exact mechanism of auto-toxicity is unclear, with medicarpins and phenols both seeming to play a role. Levels of autotoxicity in soil depends on soil type, cultivar and age of the previous crop. A soil assay can be used to measure autotoxicity. Resistant to autotoxicity also varies by cultivar, a tolerant one being 'WL 656HQ'.

Defense

When alfalfa is to be used as hay, it is usually cut and baled. Loose haystacks are still used in some areas, but bales are easier for use in transportation, storage, and feed. Ideally, the first cutting should be taken at the bud stage, and the subsequent cuttings just as the field is beginning to flower, or one-tenth bloom because carbohydrates are at their highest. When using farm equipment rather than hand-harvesting, a swather cuts the alfalfa and arranges it in windrows. In areas where the alfalfa does not immediately dry out on its own, a machine known as a mower-conditioner is used to cut the hay. The mower-conditioner has a set of rollers or flails that crimp and break the stems as they pass through the mower, making the alfalfa dry faster. After the alfalfa has dried, a tractor pulling a baler collects the hay into bales.

Several types of bales are commonly used for alfalfa. For small animals and individual horses, the alfalfa is baled into small, two-string bales, commonly named by the strands of string used to wrap it. Other bale sizes are three-string, and so on up to half-ton "square" bales – actually rectangular, and typically about 40 cm × 45 cm × 100 cm. Small square bales weigh from 25 to 30 kg depending on moisture, and can be easily hand separated into "flakes". Cattle ranches use large round bales, typically 1.4 to 1.8 m in diameter and weighing from 500 to 1,000 kg. These bales can be placed in stable stacks or in large feeders for herds of horses or unrolled on the ground for large herds of cattle. The bales can be loaded and stacked with a tractor using a spike, known as a bale spear, that pierces the center of the bale,...hieroglyph snipped... or they can be handled with a grapple on the tractor's front-end loader. A more recent innovation is large "square" bales, roughly the same proportions as the small squares, but much larger. The bale size was set so stacks would fit perfectly on a large flatbed truck. These are more common in the western United States.

When used as feed for dairy cattle, alfalfa is often made into haylage by a process known as ensiling. Rather than being dried to make dry hay, the alfalfa is chopped finely and fermented in silos, trenches, or bags, where the oxygen supply can be limited to promote fermentation. The anaerobic fermentation of alfalfa allows it to retain high nutrient levels similar to those of fresh forage, and is also more palatable to dairy cattle than dry hay. In many cases, alfalfa silage is inoculated with different strains of microorganisms to improve the fermentation quality and aerobic stability of the silage.Raw alfalfa seeds and sprouts are a source of the amino acid canavanine. Much of the canavanine is converted into other amino acids during germination so sprouts contain much less canavanine than unsprouted seeds. Canavanine competes with arginine, resulting in the synthesis of dysfunctional proteins. Raw unsprouted alfalfa has toxic effects in primates, including humans, which can result in lupus-like symptoms and other immunological diseases in susceptible individuals, and sprouts also produced these symptoms in at least some primates when fed a diet made of 40% alfalfa. Stopping consumption of alfalfa seeds can reverse the effects.

Evolution

Alfalfa seems to have originated in south-central Asia, and was first cultivated in Central Asia. According to Pliny, it was introduced to Greece in about 490 BC when the
Persians invaded Greek territory. Alfalfa cultivation is discussed in the fourth-century AD book "Opus Agriculturae" by Palladius, stating: "One sow-down lasts ten years. The crop may be cut four or six times a year... A jugerum of it is abundantly sufficient for three horses all the year... It may be given to cattle, but new provender is at first to be administered very sparingly, because it bloats up the cattle."

The medieval Arabic agricultural writer Ibn al-'Awwam, who lived in Spain in the later 12th century, discussed how to cultivate alfalfa, which he called. A 13th-century general-purpose Arabic dictionary, "Lisān al-'Arab", says that alfalfa is cultivated as an animal feed and consumed in both fresh and dried forms. It is from the Arabic that the Spanish name "alfalfa" was derived.

In the 16th century, Spanish colonizers introduced alfalfa to the Americas as fodder for their horses.

In the North American colonies of the eastern US in the 18th century, it was called "lucerne", and many trials at growing it were made, but generally without sufficiently successful results. Relatively little is grown in the southeastern United States today. Lucerne is the name for alfalfa in Britain, Australia, France, Germany, and a number of other countries. Alfalfa seeds were imported to California from Chile in the 1850s. That was the beginning of a rapid and extensive introduction of the crop over the western US States and introduced the word "alfalfa" to the English language. Since North and South America now produce a large part of the world's output, the word "alfalfa" has been slowly entering other languages.

Cultural

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 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 cows, because of its high protein content and highly digestible fiber, and secondarily for beef cattle, horses, sheep, and goats. Alfalfa hay is a widely used protein and fiber source for meat rabbits. In poultry diets, dehydrated alfalfa and alfalfa leaf concentrates are used for pigmenting eggs and meat, because of their high content in carotenoids, which are efficient for colouring egg yolk and body lipids. 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. Fresh alfalfa can cause bloating in livestock, so care must be taken with livestock grazing on alfalfa because of this hazard.

Like other legumes, its root nodules contain bacteria, "Sinorhizobium meliloti", with the ability to fix nitrogen, producing a high-protein feed regardless of available nitrogen in the soil. Its nitrogen-fixing ability 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 6.8–7.5. 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 13–20 kg/ha 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 in temperate environments, but yields have been recorded up to 20 tonnes per hectare. Yields vary with region, weather, and the crop's stage of maturity when cut. Later cuttings improve yield, but with reduced nutritional content.