Legumes (/ˈlɛɡjuːm,ləˈɡjuːm/) are plants in thepea familyFabaceae (or Leguminosae), or the fruit or seeds of such plants. When used as a dry grain for human consumption, the seeds are also calledpulses. Legumes are grown agriculturally, primarily for human consumption, but also as livestock forage andsilage, and as soil-enhancinggreen manure. Legumes produce a botanically unique type offruit – asimpledry fruit that develops from a simplecarpel and usuallydehisces (opens along a seam) on two sides.
The termpulse, as used by the United Nations'Food and Agriculture Organization (FAO), is reserved for legume crops harvested solely for the dry seed.[1] This excludesgreen beans andgreen peas, which are consideredvegetable crops. Also excluded are seeds that are mainly grown for oil extraction (oilseeds likesoybeans andpeanuts),[2] and seeds which are used exclusively for sowingforage (clovers,alfalfa).[3] However, in common usage, these distinctions are not always clearly made, and many of the varieties used for dried pulses are also used for green vegetables, with their beans in pods while young.[4]
Some Fabaceae, such asScotch broom and otherGenisteae, are leguminous but are usually not called legumes by farmers, who tend to restrict that term to food crops.[5]
The FAO recognizes 11 primary pulses, excluding green vegetable legumes (e.g. green peas) and legumes used mainly for oil extraction (e.g., soybeans and groundnuts) or used only as seed (e.g., clover and alfalfa).[6]
Dry beans (FAOSTAT code 0176,Phaseolus spp. including several species now inVigna)
Legumes are widely distributed as the third-largestland plant family in terms of number of species, behind only theOrchidaceae andAsteraceae, with about 751genera and some 19,000 known species,[7][8] constituting about seven percent of flowering plant species.[9][10]
Ammonia is converted to another form,ammonium (NH+4), usable by (some) plants, by the following reaction:
NH3 + H+ → NH+4
This arrangement means that the root nodules are sources of nitrogen for legumes, making them relatively rich in nitrogenousamino acids andprotein. Nitrogen is therefore a necessaryingredient in the production of proteins.
When a legume plant dies in the field, for example following theharvest, all of its remaining nitrogen, incorporated intoamino acids inside the remaining plant parts, is released back into the soil. In the soil, the amino acids are converted to nitrate (NO−3), making the nitrogen available to other plants, thereby serving as fertilizer for future crops.[12][13]
Legumes play a key role in thenitrogen cycle, making nitrates available to other plants in the soil.
In many traditional andorganic farming practices,crop rotation orpolyculture involving legumes is common. By alternating between legumes and non-legumes, or by growing both together for part of the growing season, the field can receive a sufficient amount of nitrogenous compounds to produce a good result without adding nitrogenous fertilizer. Legumes are often used asgreen manure.[citation needed]
Sri Lanka developed thepolyculture practice known as coconut-soybeanintercropping. Grain legumes are grown in coconut (Cocos nuficera) groves in two ways: intercropping or as a cash crop. These are grown mainly for their protein, vegetable oil and ability to uphold soil fertility.[14] However, continuous cropping after 3–4 years decrease grain yields significantly.[15]
A common pest of grain legumes that is noticed in the tropical and subtropical Asia, Africa, Australia and Oceania are minuscule flies that belong to the familyAgromyzidae, dubbed "bean flies". They are considered to be the most destructive. The host range of these flies is very wide amongst cultivated legumes. Infestation of plants starts from germination through to harvest, and they can destroy an entire crop in early stage.[16]Black bean aphids are a serious pest to broad beans and other beans. Common hosts for this pest are fathen, thistle and dock.Pea weevil andbean weevil damage leaf margins leaving characteristics semi-circular notches.Stem nematodes are very widespread but will be found more frequently in areas where host plants are grown.[17]
Seed viability decreases with longer storage time. Studies ofvetch,broad beans, and peas show that they last about 5 years in storage. Environmental factors that are important in influencing germination are relative humidity and temperature. Two rules apply to moisture content between 5 and 14 percent: the life of the seed will last longer if the storage temperature is reduced by 5 degree Celsius. Secondly, the storage moisture content will decrease if temperature is reduced by 1 degree Celsius.[20]
Cultivated legumes encompass a diverse range ofagricultural classifications, spanningforage,grain, flowering, pharmaceutical/industrial, fallow/green manure, and timber categories. A notable characteristic of many commercially cultivated legume species is their versatility, often assuming multiple roles concurrently. The extent of these roles is contingent upon the stage of maturity at which they are harvested.[citation needed]
Grain legumes are cultivated for their seeds,[21] for humans and animals to eat, or for oils for industrial uses. Grain legumes includebeans,lentils,lupins,peas, andpeanuts.[22]
Legumes are a key ingredient in vegan meat and dairysubstitutes. They are growing in use as a plant-based protein source in the world marketplace.[23][24] Products containing legumes grew by 39% in Europe between 2013 and 2017.[25]
There is acommon misconception that adding salt before cooking prevents them from cooking through. Legumes may not soften because they are old, or because ofhard water oracidic ingredients in the pot; salting before cooking results in betterseasoning.[26][27]
Forage legumes are of two broad types. Some, likealfalfa,clover, vetch (Vicia), stylo (Stylosanthes), orArachis, are sown inpasture and grazed by livestock. Others, such asLeucaena orAlbizia, are woody shrubs or trees that are either broken down by livestock or regularly cut by humans to provide fodder. Legume-based feeds improve animal performance over a diet of perennial grasses. Factors include larger consumption, faster digestion, and higherfeed conversion rate.[30]
The type of crop grown for animal rearing depends on the farming system. In cattle rearing, legume trees such asGliricidia sepium can be planted along edges of fields to provide shade for cattle, the leaves and bark are often eaten by cattle. Green manure can be grown between harvesting the main crop and the planting of the next crop.[31]
Legume species grown for their flowers includelupins, which are farmed commercially for their blooms as well as being popular in gardens worldwide. Industrially farmed legumes includeIndigofera andAcacia species, which are cultivated fordye andnatural gum production, respectively.Fallow orgreen manure legume species are cultivated to be tilled back into the soil in order to exploit the high levels of captured atmospheric nitrogen found in the roots of most legumes. Numerous legumes farmed for this purpose includeLeucaena,Cyamopsis, andSesbania species. Various legume species are farmed for timber production worldwide, including numerousAcacia species andCastanospermum australe.[citation needed]
The oldest-known domesticated beans in the Americas were found inGuitarrero Cave, an archaeological site inPeru, and dated to around the second millennium BCE.[40] Genetic analyses of the common beanPhaseolus show that it originated inMesoamerica, and subsequently spread southward, along withmaize and squash, traditional companion crops.[41] In the United States, the domesticated soybean was introduced in 1770 byBenjamin Franklin after he sent seeds to Philadelphia from France.[42]
The International Year of Pulses 2016 was declared by theSixty-eighth session of the United Nations General Assembly.[43] TheFood and Agriculture Organization of the United Nations was nominated to facilitate the implementation of the year in collaboration with governments, relevant organizations, non-governmental organizations and other relevant stakeholders. Its aim was to heighten public awareness of the nutritional benefits of pulses as part ofsustainable food production aimed towardsfood security andnutrition. The year created an opportunity to encourage connections throughout the food chain that would better use pulse-based proteins, further global production of pulses, better usecrop rotations and address challenges in the global trade of pulses.[43][44]
^Postgate, John (1998).Nitrogen Fixation (3rd ed.). Cambridge University Press.ISBN978-0-521-64853-0.
^Smil, Vaclav (2000).Cycles of Life. Scientific American Library.
^Soybean in tropical and subtropical cropping systems : proceedings of a symposium Tsukuba, Japan, 26 September – 1 October 1983. Shanhua, Taiwan : Asian Vegetable Research and Development Center. 1986. p. 57.ISBN92-9058-022-4.OCLC475699754. AVRDC No.86253.
^Shanmugasundaram, S (1991).Vegetable soybean : research needs for production and quality improvement ; proceedings of a workshop held at Kenting, Taiwan, 29 April – 2 May 1991. Taipei : The Center. p. 59.ISBN929058047X.
^Goot, P.van der (1984).Agromyzid flies of some native legume crops in Java. Shanhua, Taiwan : Asian Vegetable Research and Development Center.ISBN92-9058-006-2.
^Pest and disease control on legumes, onions, leeks, outdoor salad crops and minor vegetables. Great Britain: Alnwick : Ministry of Agriculture, Fisheries and Food ADAS. 1984. pp. 11–13.
^Sherf, Arden F.; Macnab, Alan A. (1986).Vegetable diseases and their control (Second ed.). New York : J. Wiley. pp. 79–82.ISBN0-471-05860-2.
^Cereal and grain-legume seed processing : technical guidelines. Rome: Rome : Food and Agriculture Organization of the United Nations. 1981. p. 43.ISBN92-5-100980-5.
^Kurlovich BS, Repyev SI, eds. (1995).The Gene Bank and Breeding of Grain Legumes (lupine, vetch, soya and bean). Theoretical basis of plant breeding. Vol. 111. St. Petersburg: N. I. Vavilov Institute of Plant Industry. p. 438.
^Albala, Ken (2007)."Lentils: Fertile Crescent".Beans: A History. New York:Berg Publishers. p. 18.ISBN978-0-85785-078-2.The earliest culinary texts to have survived are in the form of three cuneiform tablets dated to about 1600 BCE. ... [T]ucked away among a series of porridges there is one recipe for husked lentils ... [I]n any case it is the very oldest explicit legume recipe on earth. ... The Egyptians also used lentils as funerary offerings and in meals to feed the dead in the underworld. Large stores were found beneath Zoser's pyramid
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