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Medicago sativa L.

Fabaceae
Alfalfa, Lucerne

Source: James A. Duke. 1983. Handbook of Energy Crops. unpublished.

  1. Uses
  2. Folk Medicine
  3. Chemistry
  4. Toxicity
  5. Description
  6. Germplasm
  7. Distribution
  8. Ecology
  9. Cultivation
  10. Harvesting
  11. Yields and Economics
  12. Energy
  13. Biotic Factors
  14. Chemical Analysis of Biomass Fuels
  15. References

Uses

Alfalfa or lucerne is a highly valued legume forage, extensively cultivated in warm temperate and cool subtropical regions. It has been heralded as having the highest feeding value of all commonly grown hay crops, producing more protein per ha than any other crop for livestock. In some areas it is used in combination with corn for silage. In parts of China and Russia tender alfalfa leaves serve as a vegetable. It is used to reduce water runoff and soil erosion. It is an excellent pasture for hogs, cattle, and sheep, often in mixtures with smooth bromegrass, orchardgrass or timothy. Supplemental feeding of grain to dairy cows, sheep and fattening cattle reduces bloating and balances the high protein level of the alfalfa pastures with energy and extends the usefulness of the pasture. Alfalfa meal is presently made into pellets and used in mixed feeds for cattle, poultry and other animals. Alfalfa may be grown as a cover crop and often increases yield of succeeding crops, as potatoes, rice, cucumber, lettuce, tomatoes (increased by 10 MT/ha), corn, apples, and oranges. It is valued for bee pasturage. Extracts produce antibacterial activity against gram-positive bacteria. Powdered alfalfa is used as a diluent to adjust strength of digitalis powder, and the root has been used as an adulterant of Belladonna root. Seeds yield 8.5–11% of a drying oil suitable for making paints and varnish. Seed screenings are ground and used to a limited extent in feeds for ruminants. The seeds also contain a yellow dye. Alfalfa fiber has been used in manufacturing paper.

Folk Medicine

Seeds contain the alkaloids stachydrine and 1-homostachydrine, and are considered emmenagogue and lactigenic. They are used as a cooling poultice for boils in India. To increase weight, a cupful of 1:16 alfalfa: water infusion has been recommended. Though containing saponins, alfalfa is sold in many "health food" stores. It is considered antiscorbutic, aperient, diuretic, ecbolic, estrogenic, stimulant, and tonic, and said to aid peptic ulcers, as well as urinary and bowel problems. In Colombia, the mucilaginous fruits are used for "tos".

Chemistry

Tender shoots of alfalfa are reported to contain per 100 g 52 calories, 82.7% moisture, 6 g protein, 0.4 g fat, 9.5 g total carbohydrate, 3.1 g fiber, 1.4 g ash, 12 mg Ca, 51 mg P, 5.4 mg Fe, 3410 IU Vit A, 0.13 mg thiamine, 0.14 mg riboflavin, 0.5 mg niacin, and 162 mg ascorbic acid. Green forage of Medicago sativa is reported to contain per 100 g, 80.0% moisture, 5.2 g protein, 0.9 g fat, 3.5 g fiber, and 2.4 g ash. Silages of alfalfa contain per 100 g, 69.5% moisture, 5.7 g protein, 1.0 g fat, 8.8 g fiber, and 2.4 ash. Alfalfa whole meal and leaf meal are reported to contain per 100 g, 66 and 77 calories, 7.5 and 8.0% moisture, 16.0 and 20.4 g protein, 2.5 and 2.6 g fat, 27.3 and 17.1 g fiber, 9.1 and 11.5 g ash, respectively.The "betaine fraction" of alfalfa contains 0.785% stachydrine, 0.063% choline, 0.0069 trimethylamine, and 0.0052% betaine. The following purines have been identified: adenine, guanine, xanthine, and hypoxanthine; the pyrimidine, isocytosine; and the ribosides adenosine, guanosine, inosine, and cytidine. These factors stimulate the growth of Bacillus subtilis. Three abundant compounds in alfalfa juice are adenine (0.17%), adenosine (0.25%), and guanosine (0.36%). Nitrate concentrations greater than 0.2% can harm livestock. Prebud alfalfa in spring growth has 0.18% nitrate gradually decreasing to 0.12% at green pod stage. Prebud alfalfa in summer growth has 0.32% nitrate, gradually decreasing to 0.17% at green pod stage. Heavy N fertilization may increase nitrates to 1.0%. One study (4th Annual Alfalfa Symposium) cites 5.1 g arginine/16 g N; 3.1 g cystine and methionine, 1.5 g histidine, 4.6 g isoleucine, 7.2 g leucine, 5.6 g lysine, 4.6 g phenylalanine, 4.1 g threonine, 1.5 g tryptophane, and 4.6 g valine for alfalfa hay. Another study (C.S.I.R., 1948–1976) gives 3.5 arginine, 1.5 histidine, 4.2 lysine, 1.5 tryptophan, 4.1 phenylalanine, 1.3 methionine, 5.0 threonine, 7.9 leucine, 4.3 isoleucine, and 4.9 valine. One report gives total crude lipids as 5.2% of total dry weight, with 11% fatty acids, 10% digalactolipids, 16% monogalactolipids, 8% phospholipids, 44% neutral lipids, and 12% others. In the chloroplasts, linoleic, linolenic, and palmitic acids are the predominant acids, while stearic and oleic are low. The triglyceride fraction of alfalfa meal contains 16.9% linoleic acid, 32.2% linolenic acid, 31.0% oleic acid, and 19.9% saturated fatty acids. The phospholipid fraction (0.24% dry alfalfa meal) contained 35.2% linolenic acid, 36.8% oleic acid, 14.7% linoleic acid, and 13.3% saturated acids. Good alfalfa hay contains 138 to 198 mg chorine/100 g hay. Alfalfa meal contains 21 mg A-spinasterol/100 g. Five xanthophylls comprise 99% of the xanthophyll fraction of fresh alfalfa viz 40% lutein, 34% violaxanthin, 19% neoxanthin, 4% cryptoxanthin, and 2% zeaxanthin. Volatiles identified from alfalfa include acetone, butanone, propanal, pentanal, 2-methylpropanal, and 3-methylbutanal. Australian herbage samples contain 0.3 and 0.4% glucose, 0.3 and 0.3% fructose, 2.5 and 2.7% sucrose, and 0.6 and 0.6% oligosaccharides at early and later flowering stages. Tannin concentrations between 2.7 and 2.8% have been reported. Several coumestans occur in alfalfa, 4'-0-methylcoumestrol, 3'-methoxycoumestrol, lucernol, medicagol, sativol, trifoliol, and 11, 12-dimethoxy-7-hydroxycoumestan. Mineral constituents present include (av. values, dry basis): calcium (CaO) 2.80, phosphorus (P2O5) 0.74, potassium (K2O) 4.11, sodium (Na2O) 0.35, and magnesium (MgO) 0.44%: trace elements; barium, chromium, cobalt, copper, iron, lead, manganese, molybdenum, nickel, silver, strontium, tin, titanium, vanadium, and zinc. Alfalfa is a valuable source of vitamins A and E; it contains: b-carotene 6.24, thiamine 0.15, riboflavin 0.46, niacin 1.81, and a-tocopherol, 15.23 mg/100 g; panthothenic acid, biotin, folic acid, choline, inositol, Pyridoxine, vitamin B12, and vitamin K are also present. Fresh lucerne is rich in vitamin C (1.78 mg/g) but it loses 80% on drying. A flavone, tricin, which inhibits the movements of smooth muscle has also been isolated. Lucerne is reported to contain citric, malic, oxalic, and malonic acids; succinic, fumaric, shikimic, and quinic acids are present in minor quantities. Enzymes reported in alfalfa are amylase, emulsin, coagulase, peroxidase, erepsin, lipase, invertase, and pectinase. Among the miscellaneous constituents present in lucerne are: saponins (0.5–2% or more), an alkaloid 1-stachydrine (0.14%) which also occurs in seeds, and two ketones, myristone (C27H54O), and alfalfone (C21H42O). Hay contains the following vitamins (av. values): vitamin A, 3013 IU; thiamine, 0.29 mg; riboflavin, 1.37 mg; niacin, 3.84 mg; pantothenic acid, 1.78 mg; biotin, 0.018 mg; vitamin D, 199.5 IU; and vitamin E (as a-tocopherol) 2.60 mg/100 g. Lucerne and mixtures of lucerne and grass make good silage. When alfalfa alone is used, fermentation is enhanced by the addition of molasses. A good silage is obtained by ensuing wilted cuttings. Cattle and sheep fed on alfalfa as the sole source of forage occasionally suffer from bloat or tympanitis. The cause of bloat has not been clearly defined but it may be prevented by feeding corn or sorghum silage along with alfalfa hay or using mixed alfalfa-grass pasture. Forage cut at flowering time and dried in the field rarely causes bloating. Several methods have been developed for processing concentrates and beverages for human consumption; they involve the removal of odor and taste characteristic of alfalfa and also the fiber. A fiber-free concentrate is prepared by steeping tender leaves in cold water, followed by grinding in a blender, extraction with water, concentration and drying under vacuum. The product so obtained (yield, 13%) contains: protein 44.2, fiber 0.86, ether extr. 3.55, N-free extr. 30.69, ash 13.2, calcium 1.90, and phosphorus 0.52%, carotene 110.1 mg, ascorbic acid 51.6 mg, and thiamine 1.15 mg/100 g. Alfalfa honey gave the following average values: water 16.56, invert sugar 76.90, sucrose 4.42, dextrin 0.34, protein 0.11, acid (as formic) 0.08, and ash 0.07%. Alfalfa seeds contained: moisture 11.7, protein 33.2, fat 10.6, N-free extr. 32.0, fiber 8.1, and mineral matter 4.4%.

Toxicity

The genus Medicago has been reported to contain the following chemicals, relative toxicities of which are tabulated in Duke's "Phytotoxin Tables" (Duke, 1981b): choline, citric acid, hydrocyanic acid, limonene, malic acid, malonic acid, oxalic acid, pantothenic acid, pectin, quinic acid, saponin, shikimic acid, tannin, trigonelline, and tryptophane. Four isoflavones are reported in alfalfa (daidzein, formononetin, genistein, and biochanin A) and they, like coumestrol, produce an estrogen-like response, perhaps contributing to reproductive disturbances of cattle on high-estrogen forage. Seeds are reported to contain trypsin inhibitors. Some people are allergic to the dust generated when milling alfalfa.

Description

Perennial herb; stems erect or sometimes decumbent, 0.3–1 m long, 5–25 or more per crown, much-branched, 4-angled, glabrous or the upper part hairy; rhizome stout, penetrating the soil as much as 7–9 m; stipules united 1/3 to 1/2 length, free portion triangular-lanceolate, tapering, basally entire or with 1–2 teeth, glabrous or sparingly appressed-hairy; leaves pinnately trifoliolate; leaflets obovate-oblong, ovate or linear, tapering to base, crenate above middle mostly retuse and mucronate, 10–45 mm long, 3–10 mm broad, glabrous or appressed hairy, paler green beneath; racemes oval or rounded, 1–2.5 cm long, 1–2 cm broad, axillary, 5–40-flowered; peduncle slender, firm, always exceeding the subtending leaf, glabrous or appressed-hairy; calyx tubular, with linear-subulate teeth longer then tube; corolla yellow or blue to purple or violet, 6–15 mm long; bracteoles whitish, linear-subulate, mostly equaling the pedicel; pod slightly pubescent or glabrous, 3–9 mm in diameter, with 2–3 spirals, prominently reticulate-veined; seeds 6 or 8 per pod, yellow, castaneous or brown, ovoid, irregularly cordate or reniform. Fl. May–July (US); fr. late summer to fall.

Germplasm

Demand for better adapted, disease- and insect-resistant cvs has prompted extensive alfalfa breeding programs. Medicago sativa easily hybridizes with Medicago falcata (which is sometimes treated as a subspecies of M. sativa). Most newer cvs are synthetics, i.e., they contain a set of selected clones or seed lines produced and maintained under conditions specified by the originator. Promising plants are vegetatively propagated to obtain clonal lines and then the polycross progenies are tested to determine the combining ability of each clone. Of about 50 named cvs grown in the US, about 13 make up 74% of alfalfa acreage. 'Vernal' and 'Ranger' account for about 52%. Other cvs include: 'Buffalo', 'Hairy Peruvian' (7250 ha in 1969), 'Indian' (2450 ha), 'Cayuga', 'Cody', 'Cossack' (100,000 ha), 'Du Puits', 'Grimm' (180,000 ha), 'Ladak' (425,000 ha), 'Lahontan', 'Moapa' (resistant to spotted alfalfa aphid), 'African' (5000 ha), 'Narragansett', and 'Sonora'. 'Buffalo' is a bacterial-wilt-resistant selection from 'Kansas Common'. 'Cayuga' and 'Ranger' are also wilt resistant. 'Cody' and 'Zia' are resistant to spotted alfalfa aphid. 'Lahontan' and 'Washoe' are resistant to stem nematodes. There are many new cvs especially selected for specific areas, resistances and other agronomic purposes. Each cv is adapted to a limited area or to a specific set of climatic conditions. Assigned to the Central Asia, Near East, and Mediterranean Centers of Diversity, alfalfa or cvs thereof is reported to exhibit tolerance to aluminum, anthracnose, bacteria, disease, drought, fungus, hydrogen fluoride, high pH, heat, insects, low pH, mine, mycobacteria, nematode, salt, slope, smog, SO2, virus, weeds, waterlog, and wilt. (2n = 16, 32, 64).

Distribution

Native to southwest Asia as indicated by occurrence of wild type in the Caucasus and in mountainous regions of Afghanistan, Iran, and adjacent regions. The cultivated forms probably arose in western Persia and then spread, to become widely cultivated, often a "weed" throughout Asia, Europe, and America.

Ecology

Alfalfa shows considerable variation in form and adaptation to environment. Form of plant varies from erect to decumbent from southern subtropical areas to northern temperate regions and from lower to higher elevations. Length of vegetation period decreases from south to north and from lower to higher elevations. Many strains are adapted to different climatic plains as in hilly regions, up to an altitude of about 2400 m (to 4000 in Boliva); can withstand high temperatures of 39–41°C as well as rather low temperatures, the degree of adaptibility varying with different strains. Thrives particularly well in semi-arid regions under irrigation. Some clones that are self-sterile at low temperatures may be partially self-fertile at high temperatures. Annual rainfall of 5–6 dm is optimum (in the temperature zone), but crop will survive less. Soil moisture can be reduced to 35% of the water holding capacity of a soil before affecting photosynthesis. In areas of high rainfall of 10 dm or more, alfalfa does not grow well as a perennial. Grows on a variety of soils, but thrives on rich, friable, well-drained loamy soil with loose topsoil supplied with lime; does not tolerate waterlogging and fails to grow on acid soils. Alfalfa may be a bit more tolerant of frost and salt than wheat. Salinities of 3 mmhos reduce yields by 10%, 5 mmhos by 25%, and 8 mmhos by 50%. Deep penetrating roots make alfalfa quite drought resistant. Alfalfa is reported to range from Boreal Moist to Boreal Wet through Tropical Desert (irrigated or alluvial situations) to Dry Forest Life Zones, annual precipitation ranging from 0.9 to 27.2 (214 cases = 10.3 dm), annual temperature ranging from 4.3 to 28.5°C (213 cases = 17.7°C), and pH ranging from 4.3 to 8.7 (136 cases = 6.5). One source (Agr. Gaz NSW 1972) suggests that a pH of 6–7 is optimum, another (Parodi, 1964) suggests that 7–8 is optimum.

Cultivation

For cultivation of alfalfa, land should be well-plowed. Farm manure could be applied six weeks before planting, with additional manurings as top dressing after every third cutting. Crop is propagated by seed. As seeds have hard coat, they should be scarified or soaked in water before sowing. Fresh seeds do not germinate as well as those 2–3 years old. Seed should be inoculated with the proper strain of inoculum. Crop may be sown pure or in mixture with grasses or other legumes. Seeds sown broadcast or drilled in rows or on ridges 55–72 cm apart. Sowing on ridges as facilitates weed control. When broadcast, seed rate is 12–20 kg/ha, when sown on ridges, 10–12 kg/ha. Crop may be grown with or without irrigation. In some areas, frequent irrigation is necessary until seedlings become established. When crop is well established, a single irrigation is sufficient. Crop requires frequent hosing or cultivation to control weeds and stir the soil. Especially in the seedling stage, weed competition for light, nutrients, and water reduces alfalfa yields. Weed competition is reduced by use of clean seed, selection of planting dates, clipping weeds, and use of companion crops, but herbicide use is increasing in the US. Alfalfa is sensitive to some herbicides. Results are good with farm manure and any fertilizer containing phosphates, such as bone meal, fish meal, basic slag, rock phosphate or superphosphate (ca 250 kg/ha annually or 500 kg in alternate years). Alfalfa is often used in rotation with other crops e.g. wheat, oats or flax. Liming to pH 7 is often recommended. Generally alfalfa and alfalfa/grass mixtures with at least 1/3 alfalfa do not respond markedly to N, but respond well to P and K. Many soils lack adequate K for high yields. Apparently deficiencies of S and Mg are becoming more common. Addition of micronutrients, especially B may be necessary locally.

Harvesting

Alfalfa hay is harvested when the first flowers have opened. One cutting a year may be made at the prebloom stage without seriously damaging the stand and subsequent production. Number of cuttings per year varies from one in drier northern areas to nine or more under irrigation in southern areas; 3–4 cuttings in central areas are normal (US). For high quality hay, leaves must be retained since at early bloom stage leaves constitute about half of plant weight. All processes from field to storage (mowing, conditioning, windrowing, baling, bale handling, etc.) are mechanized in the US. Seed production, is most efficient under irrigation, but rainfed seed is produced. Row spacings of 60–110 cm are superior to closer plantings. In dense stands; nectar production, insect visitation and, subsequently, seed production often are depressed. Nearly all seed is directly combined. Use of spray defoliants has facilitated harvesting. Proper adjustment of combine is very important to avoid injury to seed. Alfalfa tolerates rotational grazing but weakens rapidly under continuous grazing. 'Ladak' is superior on rangelands, and creeping or decumbent alfalfas are better adapted for dryland conditions.

Yields and Economics

Forage yields are 5–75 MT/ha per year (with 8–12 cuttings per year). Seed yields are 186–280 kg/ha annually. Alfalfa is estimated to fix 83–594 kg N/ha/yr (Miller, 1976). About 10 years ago, this most valuable of common hay crops had an estimated hectarage of 33 million, the US, USSR, and Argentina producing 70% of world production, France, Italy, Canada, and Australia producing another 20%. Alfalfa accounts for about 60% of total US hay production.

Energy

In UK, the best options for annual energy plantation crops would probably involve the use of grasses, lucerne, clover, or forage cereals. With total cultivation and harvesting costs at $700/ha/yr and fresh weight yield of 70 MT/ha/yr, the DM yield would be 15.75 MT/ha/yr and the output of gross energy 275 GJ/ha/yr. ($2.55 per GJ gross energy before transportation and storage and a minimum biogas cost of $8.75/GJ.) (Palz and Chartier, 1980). Shortly after the US energy crisis of 1973, Jim and Peggy Duke (1975) offered one simplistic scenario: What if, instead of making auto fuel from the fossilized remains of plants (oil and coal), we made it from fresh plant tissue? High-quality, low-pollution fuel is as available from fresh plants as gasoline is from oil. We contend that by growing plants with conversion to fuel in mind, America could become self-sufficient in energy, utilize some of its organic wastes to build soils, and achieve many other benefits. Assume we have 62.5 million acres of unused and marginal land available for energy farming. Now let us develop a concept we inherited from the American Indians—the intercropping of a legume like alfalfa with a cereal like corn, adding some organic matter like sewage sludge. Alfalfa, like most legumes, takes nitrogen from the atmosphere and puts it in the soil—nearly 200 pounds per acre. It would take nearly a barrel of oil to manufacture that much inorganic nitrogen fertilizer. Alfalfa grows well in the cool months, producing enough vegetation to yield the energy equivalent of 2 to 7 barrels of oil per acre. Basing estimates on average alfalfa hay yields, participants at the Fourth Annual Alfalfa Symposium concluded that we could get nearly a ton of leaf protein per acre from alfalfa. This would mean 55 million tons of protein from 62.5 million acres—about 10 times what Americans need in their diet. Residues remaining after protein extraction would yield the equivalent of 250 million barrels of oil in residues. This alone could cut gasoline imports significantly. If we fertilized with sewage sludge, our 62.5 million acres of alfalfa could probably meet President Ford's target import reduction of one million barrels a day, but also provide protein for the US with plenty for export. Duke (1981a) reports DM yields of 0–37 MT/ha/yr (24 in Bolivia, 11 in Czechoslovakia, 10–11 in Cyprus, 11 in Egypt, 7 in France, 6–9 in Germany, 8–11 in Hungary, 3–21 in Italy, 0–24 in New Zealand, 10–13 in Romania, 29 in Turkistan, 7–37 in USA, 2–21 in USSR, and 8–12 in Yugoslavia.

Biotic Factors

Nearly all alfalfas require the flowers to be tripped for pollination to take place; this amounts to release of the sexual column from the keel of the flower. Many types of bees can serve as trippers, e.g. the alfalfa leaf-cutter bee (Megachile rotundata), alkali bee (Nomia melandri), honeybees (Apis mellifera), and bumblebees. In North America, alfalfa-pollinating genera, listed with the number of effective species, are as follows: Apis (1), Bombus (7), Xylocopa (1), Anthophora (1), Tetralonia (1), Osmia (2), Megachile (10), Hoplitis (1), Nomia (1), Agapostemon (2), Halictus (3), Evylaeus (1), Lasioglossum (1), Andrena (2), Calliopsis (1). Over 100 species of fungi have been reported to cause diseases on alfalfa. Among the most serious are the following: Colletotrichum trifolii, (anthracnose), Pseudopeziza medicaginis, P. jonesii, Leptosphaerulina briosiana, Stemphylium spp., Uromyces striatus (rust), Peronospora trifoliorum (downy mildew), Phoma medicaginis (spring black stem and leafspot), Ascochyta imperfecta (leafspot), Sclerotinia trifoliorum (stem rot), Fusarium spp., and Phytophthora megasperma (root rot). Bacterial wilt, caused by Corynebacterium insidiosum, is one of the most destructive alfalfa diseases. Virus diseases include: Alfalfa mosaic, Lucerne mosaic, Yellow-green stripe mosaic, Rugose leaf-curl and Witches broom virus of lucerne. Parasitic plants attacking alfalfa include: Orobanche lutea, Cuscuta australis, C. arvensis, C. campestris, C. chinensis, C. epithymum, C. gronovii, C. indecora, C. pentagona, C. planiflora, C. racemosa, C. suaveolens, and C. trifolia.. Nematodes attacking alfalfa are numerous and belong to several genera. Some are found in the roots, while others are only found in the soil near the roots. Stem-nematodes (Ditylenchus dipsaci) and root-knot nematodes (Meloidogyne spp.) cause much damage; the cultivars, 'Lahontan' and 'Washoe' are resistant to stem nematodes. Among important insect pests of alfalfa are the following: alfalfa weevil (Hypera postica), to which there are some resistant cultivars; spotted alfalfa aphid (Therioaphis maculata), and pea aphid (Acrythosiphon pisum), to both of which there are resistant cultivars; Potato leafhopper causing alfalfa yellows (Empoasca fabae) and meadow spittlebug (Philaenus spumarius). Lygus bugs, seed chalcids and alfalfa weevils are most harmful to seed production. About 10 years ago, this most valuable of common hay crops had an estimated hectarage of 33 million, the USA, USSR, and Argentina producing another 20%, alfalfa accounts for ca 60% of total US hay tonnage.

Chemical Analysis of Biomass Fuels

Analysing 62 kinds of biomass for heating value, Jenkins and Ebeling (1985) reported a spread of 18.45 to 17.36 MJ/kg, compared to 13.76 for weathered rice straw to 23.28 MJ/kg for prune pits. On a % DM basis, the seed straw contained 72.60% volatiles, 7.25% ash, 20.15% fixed carbon, 46.76% C, 5.40% H, 40.72% O, 1.00% N, 0.02% S, 0.03% Cl, and undetermined residue.

References

Complete list of references for Duke, Handbook of Energy Crops
Last update Wednesday, January 7, 1998 by aw