Acereal is agrass cultivated for its ediblegrain. Cereals are the world's largest crops, and are thereforestaple foods. They includerice,wheat,rye,oats,barley,millet, andmaize. Edible grains from other plant families, such asbuckwheat andquinoa, arepseudocereals. Most cereals areannuals, producing one crop from each planting, though rice is sometimes grown as aperennial. Winter varieties are hardy enough to be planted in the autumn, becoming dormant in the winter, and harvested in spring or early summer; spring varieties are planted in spring and harvested in late summer. The term cereal is derived from the name of the Roman goddess of grain crops and fertility,Ceres.
Cereals weredomesticated in theNeolithic around 8,000 years ago. Wheat and barley were domesticated in theFertile Crescent; rice was domesticated in East Asia, andsorghum and millet were domesticated in West Africa. Maize was domesticated byIndigenous peoples of the Americas in southern Mexico about 9,000 years ago. In the 20th century, cereal productivity was greatly increased by theGreen Revolution. This increase in production has accompanied agrowing international trade, with some countries producing large portions of the cereal supply for other countries.
Cereals provide food eaten directly aswhole grains, usually cooked, or they are ground toflour and made intobread,porridge, and other products. Cereals have a highstarch content, enabling them to be fermented into alcoholic drinks such asbeer. Cereal farming has a substantialenvironmental impact, and is often produced in high-intensitymonocultures. The environmental harms can be mitigated bysustainable practices which reduce the impact on soil and improve biodiversity, such asno-till farming andintercropping.
Wheat, barley,rye, andoats were gathered and eaten in theFertile Crescent during the earlyNeolithic. Cereal grains 19,000 years old have been found at theOhalo II site inIsrael, with charred remnants of wild wheat and barley.[1]
During the same period, farmers inChina began tofarm rice and millet, using human-made floods andfires as part of their cultivation regimen.[2][3] The use ofsoil conditioners, includingmanure, fish,compost andashes, appears to have begun early, and developed independently in areas of the world includingMesopotamia, theNile Valley, and Eastern Asia.[4]
Cereals that became modern barley and wheat weredomesticated some 8,000 years ago in the Fertile Crescent.[5] Millets and rice were domesticated in East Asia, whilesorghum and other millets were domesticated in sub-Saharan West Africa, primarily as feed for livestock.[6]Maize arose from a single domestication inMesoamerica about 9,000 years ago.[7]
Roman harvesting machine
In these agricultural regions, religion was often shaped by the divinity associated with the grain and harvests. In the Mesopotamian creation myth, an era of civilization is inaugurated by the grain goddessAshnan.[8] The Roman goddessCeres presided over agriculture, grain crops, fertility, and motherhood;[9] the term cereal is derived from Latincerealis, "of grain", originally meaning "of [the goddess] Ceres".[10] Several gods of antiquity combined agriculture and war: the HittiteSun goddess of Arinna, the CanaaniteLahmu and the RomanJanus.[11]
Complexcivilizations arose where cereal agriculture created a surplus, allowing for part of the harvest to be appropriated from farmers, allowing power to be concentrated in cities.[12]
During the second half of the 20th century, there was a significant increase in the production of high-yield cereal crops worldwide, especially wheat and rice, due to theGreen Revolution, a technological change funded by development organizations.[15] The strategies developed by the Green Revolution included mechanized tilling,monoculture, nitrogen fertilizers, and breeding of new strains of seeds. These innovations focused on fending off starvation and increasing yield-per-plant, and were very successful in raising overall yields of cereal grains, but paid less attention to nutritional quality.[16] These modern high-yield cereal crops tend to havelow-quality proteins, withessential amino acid deficiencies, are high incarbohydrates, and lack balancedessential fatty acids,vitamins,minerals and other quality factors.[16] So-calledancient grains andheirloom varieties have seen an increase in popularity with the"organic" movements of the early 21st century, but there is a tradeoff in yield-per-plant, putting pressure on resource-poor areas asfood crops are replaced withcash crops.[17]
Structure of a cereal,wheat. A: Plant; B ripe ear of grains; 1spikelet before flowering; 2 the same, flowering and spread, enlarged; 3 flowers withglumes; 4stamens 5pollen; 6 and 7 ovaries with juice scales; 8 and 9 parts of the scar; 10 fruit husks; 11–14 grains, natural size and enlarged.
Cereals are grasses, in thePoaceae family, that produce ediblegrains. A cereal grain is botanically acaryopsis, afruit where theseed coat is fused with thepericarp.[18][19] Grasses havestems that are hollow except at thenodes and narrow alternate leaves borne in two ranks.[20] The lower part of each leaf encloses the stem, forming a leaf-sheath. The leaf grows from the base of the blade, an adaptation that protects the growing meristem from grazing animals.[20][21] The flowers are usuallyhermaphroditic, with the exception ofmaize, and mainlyanemophilous or wind-pollinated, although insects occasionally play a role.[20][22]
All cereal crops are cultivated in a similar way. Most areannual, so after sowing they are harvested just once.[25] An exception is rice, which although usually treated as an annual can survive as aperennial, producing aratoon crop.[26] Cereals adapted to atemperate climate, such asbarley,oats,rye,spelt,triticale, andwheat, are called cool-season cereals. Those preferring atropical climate, such asmillet andsorghum, are called warm-season cereals.[25][27][28] Cool-season cereals, especially rye, followed by barley, are hardy; they grow best in fairly cool weather, and stop growing, depending on variety, when the temperature goes above around 30 °C or 85 °F. Warm-season cereals, in contrast, require hot weather and cannot tolerate frost.[25] Cool-season cereals can be grown in highlands in the tropics, where they sometimes deliver several crops in a single year.[25]
In the tropics, warm-season cereals can be grown at any time of the year. In temperate zones, these cereals can only be grown when there is no frost. Most cereals are planted intilled soils, which reduces weeds and breaks up the surface of a field. Most cereals need regular water in the early part of their life cycle. Rice is commonly grown in flooded fields,[29] though some strains are grown on dry land.[30] Other warm climate cereals, such as sorghum, are adapted to arid conditions.[31]
Cool-season cereals are grown mainly in temperate zones. These cereals often have both winter varieties for autumn sowing, winter dormancy, and early summer harvesting, and spring varieties planted in spring and harvested in late summer. Winter varieties have the advantage of using water when it is plentiful, and permitting a second crop after the early harvest. They flower only in spring as they requirevernalization, exposure to cold for a specific period, fixed genetically. Spring crops grow when it is warmer but less rainy, so they may need irrigation.[25]
Cereal strains are bred for consistency and resilience to the local environmental conditions. The greatest constraints onyield areplant diseases, especiallyrusts (mostly thePuccinia spp.) andpowdery mildews.[32] Fusarium head blight, caused byFusarium graminearum, is a significant limitation on a wide variety of cereals.[33] Other pressures includepest insects and wildlife like rodents and deer.[34][35] In conventional agriculture, some farmers will applyfungicides or pesticides
Annual cereals die when they have come to seed, and dry up. Harvesting begins once the plants and seeds are dry enough. Harvesting in mechanized agricultural systems is bycombine harvester, a machine which drives across the field in a single pass in which it cuts the stalks and thenthreshes andwinnows the grain.[25][36] In traditional agricultural systems, mostly in theGlobal South, harvesting may be by hand, using tools such asscythes andgrain cradles.[25] Leftover parts of the plant can be allowed to decompose, or collected asstraw; this can be used for animal bedding, mulch, and a growing medium for mushrooms.[37] It is used in crafts such as building withcob orstraw-bale construction.[38]
If cereals are not completely dry when harvested, such as when the weather is rainy, the stored grain will be spoilt bymould fungi such asAspergillus andPenicillium.[25][39] This can be prevented by drying it artificially. It may then be stored in agrain elevator orsilo, to be sold later. Grain stores need to be constructed to protect the grain from damage by pests such as seed-eating birds androdents.[25]
An indigenous Mexican woman prepares maizetortillas, 2013
When the cereal is ready to be distributed, it is sold to a manufacturing facility that first removes the outer layers of the grain for subsequentmilling for flour or other processing steps, to produce foods such as flour,oatmeal, orpearl barley.[40] In developing countries, processing may be traditional, in artisanal workshops, as withtortilla production in Central America.[41]
Most cereals can be processed in a variety of ways.Rice processing, for instance, can create whole-grain or polished rice, or rice flour. Removal of the germ increases the longevity of grain in storage.[42] Some grains can bemalted, a process of activating enzymes in the seed to cause sprouting that turns the complex starches into sugars before drying.[43][44] These sugars can be extracted for industrial uses and further processing, such as for makingindustrial alcohol,[45]beer,[46]whisky,[47] orrice wine,[48] or solddirectly as a sugar.[49] In the 20th century,industrial processes developed around chemically altering the grain, to be used for other processes. In particular,maize can be altered to produce food additives, such ascorn starch[50] andhigh-fructose corn syrup.[51]
Excellent soil structure in land inSouth Dakota withno-till farming using acrop rotation of maize, soybeans, and wheat accompanied bycover crops. The main crop has been harvested but the roots of the cover crop are still visible in autumn.
Some of the impacts of growing cereals can be mitigated by changing production practices. Tillage can be reduced byno-till farming, such as by direct drilling of cereal seeds, or by developing and plantingperennial crop varieties so that annual tilling is not required. Rice can be grown as aratoon crop;[26] and other researchers are exploring perennial cool-season cereals, such askernza, being developed in the US.[58]
Fertilizer and pesticide usage may be reduced in somepolycultures, growing several crops in a single field at the same time.[59] Fossil fuel-basednitrogen fertilizer usage can be reduced byintercropping cereals withlegumes whichfix nitrogen.[60] Greenhouse gas emissions may be cut further by more efficient irrigation or by water harvesting methods likecontour trenching that reduce the need for irrigation, and by breeding new crop varieties.[61]
Some cereals such as rice require little preparation before human consumption. For example, to make plaincooked rice, rawmilled rice is washed and boiled.[62] Foods such asporridge[63] andmuesli may be made largely of whole cereals, especially oats, whereas commercialbreakfast cereals such asgranola may be highly processed and combined with sugars,oils, and other products.[64]
A cereal grain consists of starchyendosperm,germ, andbran. Wholemeal flour contains all of these; white flour is without some or all of the germ or bran.[71][72]
Cereals and their related byproducts such ashay are routinelyfed to farm animals. Common cereals as animal food include maize, barley, wheat, and oats. Moist grains may be treated chemically or made intosilage; mechanically flattened or crimped, and kept in airtight storage until used; or stored dry with a moisture content of less than 14%.[75] Commercially, grains are often combined with other materials and formed into feed pellets.[76]
Some cereals are deficient in the essential amino acidlysine, obliging vegetarian cultures to combine their diet of cereal grains withlegumes to obtain a balanced diet. Many legumes, however, are deficient in the essential amino acidmethionine, which grains contain. Thus,a combination of legumes with grains forms a well-balanced diet for vegetarians. Such combinations includedal (lentils) with rice bySouth Indians andBengalis,beans withmaize tortillas,tofu with rice, andpeanut butter with wholegrain wheat bread (as sandwiches) in several other cultures, including the Americas.[79] Forfeeding animals, the amount ofcrude protein measured in grains is expressed as grain crude protein concentration.[80]
A grain elevator on fire in Ukraine, 2023. The Russian invasion of Ukraine disrupted its wheat exports and the globalcereal trade.
Cereals constitute the world's largest commodities by tonnage, whether measured by production[82] or by international trade. Several major producers of cereals dominate the market.[83] Because of the scale of the trade, some countries have become reliant on imports, thus cerealspricing or availability can have outsized impacts on countries with a food trade imbalance and thusfood security.[84]Speculation, as well as other compounding production and supply factors leading up to the2007–2008 financial crises, created rapid inflation of grain prices during the2007–2008 world food price crisis.[85] Other disruptions, such as climate change or war related changes to supply or transportation can create further food insecurity; for example theRussian invasion of Ukraine in 2022 disrupted Ukrainian and Russian wheat supplies causing aglobal food price crisis in 2022 that affected countries heavily dependent on wheat flour.[86][87][88][89]
Cereals are the world's largest crops by tonnage of grain produced.[82] Three cereals, maize, wheat, and rice, together accounted for 89% of all cereal production worldwide in 2012, and 43% of the global supply offood energy in 2009,[90] while the production of oats and rye has drastically fallen from their 1960s levels.[91]
Other cereals not included in the U.N.'sFood and Agriculture Organization statistics includewild rice, which is grown in small amounts in North America, andteff, an ancient grain that is a staple inEthiopia.[92] Teff is grown in sub-Saharan Africa as a grass primarily for feeding horses. It is high in fiber and protein. Its flour is often used to makeinjera. It can be eaten as a warm breakfast cereal likefarina with a chocolate or nutty flavor.[92]
Production of cereals worldwide, by country in 2021
The table shows the annual production of cereals in 1961, 1980, 2000, 2010, and 2019/2020.[a][93][91]
A staple food of people in the Americas, Africa, and oflivestock worldwide; often called corn in North America, Australia, and New Zealand. A large portion of maize crops are grown for purposes other than human consumption.[92]
The primary cereal of temperate regions. It has a worldwide consumption but it is a staple food of North America, Europe, Australia, New Zealand, Argentina, Brazil and much of theGreater Middle East.Wheat gluten-based meat substitutes are important in the Far East (albeit less thantofu) and are said to resemble meat texture more than others.[92]
Cereals are the most tradedcommodities by quantity in 2021, with wheat, maize, and rice the main cereals involved. The Americas and Europe are the largest exporters, and Asia is the largest importer.[83] The largest exporter of maize is the US, while India is the largest exporter of rice. China is the largest importer of maize and of rice. Many other countries trade cereals, both as exporters and as importers.[83] Cereals aretraded as futures on worldcommodity markets, helping to mitigate the risks of changes in price for example, if harvests fail.[95]
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