{{short description|Species of grass cultivated as a food crop}}
{{redirect|Corn|other uses|Corn (disambiguation)|and|Maize (disambiguation)}}
{{Distinguish|Maze}}
{{pp-semi-indef|small=yes}}
{{good article}}
{{Use mdy dates|date=January 2016}}
{{Speciesbox
|name = Maize
|image = Koeh-283.jpg
|image_caption = Includes male and female flowers
|image_alt = [[Botanical illustration]] showing male and female flowers
|genus = Zea (plant)
|species = mays
|status = LC
|status_system = IUCN3.1
|status_ref = {{cite journal |last1=Contreras |first1=A. |last2=Ruíz Corral |first2=J. A. |last3=Menjívar |first3=J. |last4=Aragón Cuevas |first4=F. |last5=González Ledesma |first5=M. |last6=Sánchez |first6=J. J. |date=2019 |title=Zea mays |journal=IUCN Red List of Threatened Species 2019: E.T77726273A77726310 |doi=10.2305/IUCN.UK.2019-2.RLTS.T77726273A77726310.en |doi-access=free }}
|authority = [[Carl Linnaeus|L.]]
}}
'''Maize''' ({{IPAc-en|'|m|eɪ|z}}; '''''Zea mays'''''), also known as '''corn''', is a tall stout [[Poaceae|grass]] that produces [[cereal grain]]. The leafy [[Plant stem|stalk]] of the plant gives rise to male [[inflorescence]]s or tassels which produce [[pollen]], and female inflorescences called [[ear (botany)|ears]]. The ears yield grain, known as [[Corn kernels|kernels]] or seeds. In modern commercial varieties, these are usually yellow or white; other varieties can be of many colors. Maize was domesticated by [[indigenous peoples of Mexico|indigenous peoples in southern Mexico]] about 9,000 years ago from wild [[teosinte]].{{cite journal |last1=Lohse |first1=Jon C. |last2=Morgan |first2=Molly |last3=Jones |first3=John G. |display-authors=etal |title=Early Maize in the Maya Area |journal=Latin American Antiquity |volume=33 |issue=4 |year=2022 |pages=677–692 |jstor=27362456}} Native Americans planted it alongside [[bean]]s and [[Cucurbita|squash]]es in the [[Three Sisters (agriculture)|Three Sisters]] [[polyculture]].
Maize relies on humans for its propagation. Since the [[Columbian exchange]], it has become a [[staple food]] in many parts of the world, with the [[List of most valuable crops and livestock products|total production of maize surpassing]] that of [[wheat]] and [[rice]]. Much maize is used for [[animal feed]], whether as grain (fodder) or as the whole plant, which can either be baled as forage or made into the more palatable [[silage]]. Sugar-rich varieties called [[sweet corn]] are grown for human consumption, while [[field corn]] varieties are used for animal feed, for uses such as [[cornmeal]] or [[masa]], [[corn starch]], [[corn syrup]], pressing into [[corn oil]], alcoholic beverages like [[bourbon whiskey]], and as chemical feedstocks including [[Corn ethanol|ethanol]] and other [[biofuel]]s.
Maize is cultivated throughout the world; a greater weight of maize is produced each year than any other grain. In 2020, world production was 1.1 billion tonnes. It is afflicted by many [[Pest (organism)|pests]] and [[List of maize diseases|diseases]]; two major [[insect]] pests, [[European corn borer]] and [[Diabrotica|corn rootworms]], have each caused annual losses of a billion dollars in the United States. Modern [[plant breeding]] has greatly increased output and qualities such as nutrition, drought tolerance, and tolerance of pests and diseases. Much maize is now [[genetically modified]].
As a food, maize is used to make a wide variety of dishes including Mexican [[tortilla]]s and [[tamale]]s, Italian [[polenta]], and American [[hominy]] [[grits]]. Maize [[Protein (nutrient)|protein]] is low in some [[essential amino acid]]s, and the [[Niacin (nutrient)|niacin]] it contains only becomes available if [[nixtamalization|freed by alkali treatment]]. In pre-Columbian [[Mesoamerica]], maize was deified as [[Maya maize god|a maize god]] and depicted in sculptures.
== Description ==
{{Dark mode invert|image=y|[[File:Maize plant diagram, large labels.svg|frameless|right|upright=0.8|alt=Parts of a maize plant]]}}
Maize is a tall [[Annual plant|annual]] grass with a single stem, ranging in height from {{convert|1.2|to|4|m|ft|abbr=on|0}}.{{cite book |last1=Solaimalai |first1=A. |title=Maize Crop: Improvement, Production, Protection and Post Harvest Technology |last2=Anantharaju |first2=P. |last3=Irulandi |first3=S. |last4=Theradimani |first4=M. |date=2020-05-10 |publisher=[[CRC Press]] |isbn=978-1-000-17695-7 |chapter=6. Growth and Development Stages |chapter-url=https://books.google.com/books?id=T7XjDwAAQBAJ&pg=PT60}} The long narrow leaves arise from the [[node (botany)|node]]s or joints, alternately on opposite sides on the stalk. Maize is [[monoecious]], with separate male and female flowers on the same plant. At the top of the stem is the tassel, an [[inflorescence]] of male flowers; their anthers release pollen, which is [[Anemophily|dispersed by wind]]. The female inflorescence, some way down the stem from the tassel, is first seen as a silk, a bundle of soft [[Stigma (botany)|tubular hairs]], one for the [[carpel]] in each female flower, which develops into a kernel (often called a seed. Botanically, as in all grasses, it is a fruit, fused with the seed coat to form a [[caryopsis]]){{cite web |title=Caryopsis |url=http://www.merriam-webster.com/dictionary/caryopsis |access-date=January 9, 2024 |publisher=[[Merriam-Webster]]}} when it is pollinated. A whole female inflorescence develops into an ear or [[corncob]], enveloped by multiple leafy layers or husks. The {{vanchor|Ear leaf|text=ear leaf}} is the leaf most closely associated with a particular developing ear. This leaf and those above it contribute over three quarters of the carbohydrate ([[starch]]) that fills the grain.{{cite web |title=Before applying fungicides to corn: Stop! Look! Consider! |url=http://crops.extension.iastate.edu/encyclopedia/applying-fungicides-corn-stop-look-consider |access-date=2021-07-24 |website=Integrated Crop Management |publisher=[[Iowa State University Extension]]}}
The grains are usually yellow or white in modern varieties; other varieties have orange, red, brown, [[blue corn|blue]], [[purple corn|purple]], or black grains. They are arranged in 8 to 32 rows around the cob; there can be up to 1200 grains on a large cob.{{cite book |last=Davidson |first=Alan |title=The Oxford Companion to Food |date=2014 |publisher=[[Oxford University Press]] |isbn=978-0-19-967733-7 |edition=3rd |pages=484–486 |chapter=Maize}} Yellow maizes derive their color from [[carotenoid]]s; red maizes are colored by [[anthocyanin]]s and [[phlobaphene]]s; and orange and green varieties may contain combinations of these pigments.{{cite journal |last1=Chatham |first1=Laura A. |last2=Paulsmeyer |first2=Michael |last3=Juvik |first3=John A. |date=2019 |title=Prospects for economical natural colorants: insights from maize |journal=Theoretical and Applied Genetics |volume=132 |issue=11 |pages=2927–2946, and Figure 1 |doi=10.1007/s00122-019-03414-0 |pmid=31451836 |s2cid=201729476}}
Maize has short-day [[photoperiodism]], meaning that it requires nights of a certain length to flower. Flowering further requires [[growing degree day|enough warm days]] above {{convert|10|°C|°F|abbr=on}}. The control of flowering is set genetically; the physiological mechanism involves the [[phytochrome]] system. Tropical cultivars can be problematic if grown in higher latitudes, as the longer days can make the plants grow tall instead of setting seed before winter comes. On the other hand, growing tall rapidly could be convenient for producing biofuel.
Immature maize shoots accumulate a powerful antibiotic substance, 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one ([[DIMBOA]]), which provides a measure of protection against a wide range of pests.{{Cite journal |last1=Smith |first1=C. Michael |last2=Clement |first2=Stephen L. |year=2012 |title=Molecular Bases of Plant Resistance to Arthropods |journal=Annual Review of Entomology |volume=57 |issue=1 |pages=309–328 |doi=10.1146/annurev-ento-120710-100642 |pmid=21910639}} Because of its shallow roots, maize is susceptible to droughts, intolerant of nutrient-deficient soils, and prone to being uprooted by severe winds.{{cite web |date=October 2, 2008 |title=Corn Stalk Lodging |url=http://www.dekalb.ca/content/pdf/corn_stalk_lodging.pdf |archive-url=https://web.archive.org/web/20090225054032/http://www.dekalb.ca/content/pdf/corn_stalk_lodging.pdf |archive-date=February 25, 2009 |access-date=February 23, 2009 |publisher=[[Monsanto Company|Monsanto]] Imagine}}
The pollen is an [[allergen]], but most of it falls within a few meters of the tassel and the risk is largely restricted to farm workers.{{cite journal |last1=Oldenburg |first1=Marcus |last2=Petersen |first2=Arnd |last3=Baur |first3=Xaver |date=2011 |title=Maize pollen is an important allergen in occupationally exposed workers |journal=Journal of Occupational Medicine and Toxicology |volume=6 |issue=1 |page=32 |doi=10.1186/1745-6673-6-32 |pmc=3269392 |pmid=22165847 |doi-access=free}}
{{cite journal |last1=Ranere |first1=Anthony J. |last2=Piperno |first2=Dolores R. |last3=Holst |first3=Irene |last4=Dickau |first4=Ruth |last5=Iriarte |first5=José |year=2009 |title=Starch grain and phytolith evidence for early ninth millennium B.P. maize from the Central Balsas River Valley, Mexico |journal=[[Proceedings of the National Academy of Sciences]] |volume=106 |issue=13 |pages=5019–5024 |bibcode=2009PNAS..106.5019P |doi=10.1073/pnas.0812525106 |pmc=2664021 |pmid=19307570 |doi-access=free}} Doebley and colleagues showed in 2002 that maize had been domesticated only once, about 9,000 years ago, and then spread throughout the Americas.{{cite journal |last1=Matsuoka |first1=Y. |last2=Vigouroux |first2=Y. |last3=Goodman |first3=M. M. |last4=Sanchez G. |first4=J. |last5=Buckler |first5=E. |last6=Doebley |first6=J. |display-authors=3 |year=2002 |title=A single domestication for maize shown by multilocus microsatellite genotyping |journal=[[Proceedings of the National Academy of Sciences]] |volume=99 |issue=9 |pages=6080–4 |bibcode=2002PNAS...99.6080M |doi=10.1073/pnas.052125199 |pmc=122905 |pmid=11983901 |doi-access=free}}
Maize pollen dated to 7,300 years ago from [[San Andrés (Mesoamerican site)|San Andres, Tabasco]] has been found on the Caribbean coast. A primitive corn was being grown in southern Mexico, Central America, and northern South America 7,000 years ago. Archaeological remains of early maize ears, found at [[Guila Naquitz Cave]] in the [[Oaxaca Valley]], are roughly 6,250 years old; the oldest ears from caves near [[Tehuacán, Puebla|Tehuacan]], Puebla, are 5,450 years old.{{cite journal |last=Roney |first=John |date=Winter 2009 |title=The Beginnings of Maize Agriculture |journal=Archaeology Southwest |volume=23 |issue=1 |page=4}}
=== Spreading to the north ===
Around 4,500 years ago, maize began to spread to the north. Maize was first cultivated at several sites in New Mexico and Arizona about 4,100 years ago. During the first millennium AD, maize cultivation spread more widely in the areas north. In particular, the large-scale adoption of maize agriculture and consumption in eastern North America took place about A.D. 900. Native Americans cleared large forest and grassland areas for the new crop.{{cite journal |last1=Emerson |first1=Thomas E. |last2=Hedman |first2=Kristin M. |last3=Simon |first3=Mary L. |date=2005 |title=Marginal Horticulturalists or Maize Agriculturalists? Archaeobotanical, Paleopathological, and Isotopic Evidence Relating to Langford Tradition Maize Consumption |journal=Midcontinental Journal of Archaeology |volume=30 |issue=1 |pages=67–118 |doi=10.1179/mca.2005.003 |jstor=20708222 |s2cid=129150225}} The rise in maize cultivation 500 to 1,000 years ago in what is now the [[southeastern U.S.]] corresponded with a decline of freshwater [[mussel]]s, which are very sensitive to environmental changes.{{cite journal |last1=Peacock |first1=Evan |last2=Haag |first2=Wendell R. |last3=Warren |first3=Melvin L. Jr |year=2005 |title=Prehistoric decline in freshwater mussels coincident with the advent of maize agriculture |url=https://www.srs.fs.usda.gov/pubs/ja/ja_peacock001.pdf |journal=[[Conservation Biology (journal)|Conservation Biology]] |volume=19 |issue=2 |pages=547–551 |bibcode=2005ConBi..19..547P |doi=10.1111/j.1523-1739.2005.00036.x |s2cid=3679709}}
=== Names ===
The name ''maize'' derives from the Spanish form {{lang|es|maíz}} of the [[Taíno language|Taíno]] {{lang|tnq|mahis}}.{{OED|maize, n. (and adj.)|5706589143}} The Swedish botanist [[Carl Linnaeus]] used the common name maize as the species epithet in ''Zea mays''.{{cite journal |last1=Ranum |first1=Peter |last2=Peña-Rosas |first2=Juan Pablo |last3=Garcia-Casal |first3=Maria Nieves |date=April 2014 |title=Global maize production, utilization, and consumption |journal=[[Annals of the New York Academy of Sciences]] |volume=1312 |issue=1 |pages=105–112 |bibcode=2014NYASA1312..105R |doi=10.1111/nyas.12396 |pmid=24650320 |s2cid=4640742 |doi-access=free}} The name ''maize'' is preferred in formal, scientific, and international usage as a [[common name]] because it refers specifically to this one grain, unlike ''corn'', which has a complex variety of meanings that vary by context and geographic region.{{cite book |last=Ensminger |first=Audrey H. |title=Foods and Nutrition Encyclopedia, 2nd ed. |publisher=[[CRC Press]] |year=1994 |isbn=978-0-8493-8980-1 |page=[{{google books |plainurl=y |id=XMA9gYIj-C4C|page=479}} 479] |quote=The word "maize" is preferred in international usage because in many countries the term "corn", the name by which the plant is known in the United States, is synonymous with the leading cereal grain; thus, in England "corn" refers to wheat, and in Scotland and Ireland it refers to oats.}} Most countries primarily use the term ''maize'', and the name ''corn'' is used mainly in the U.S. and a handful of other English-speaking countries.{{cite book |last=McLellan Plaisted |first=Susan |url=https://www.oxfordreference.com/display/10.1093/acref/9780199734962.001.0001/acref-9780199734962-e-0218 |title=The Oxford Encyclopedia of Food and Drink in America |date=2013 |publisher=[[Oxford University Press]] |isbn=978-0-19-973922-6 |editor-last1=Smith |editor-first1=Andrew |edition=2nd |location=New York |chapter=Corn |quote=The use of the word "corn" for what is termed "maize" by most other countries is peculiar to the United States. Europeans who were accustomed to the names "wheat corn", "barley corn", and "rye corn" for other small-seeded cereal grains referred to the unique American grain maize as "Indian corn." The term was shortened to just "corn", which has become the American word for the plant of American genesis. |access-date=15 February 2023}}{{cite web |last=Espinoza |first=Mauricio |date=April 1, 2015 |title='All Corn Is the Same,' and Other Foolishness about America's King of Crops |url=https://cfaes.osu.edu/news/articles/'all-corn-is-the-same'-and-other-foolishness-about-america's-king-crops |url-status=live |archive-url=https://web.archive.org/web/20201203073514/https://cfaes.osu.edu/news/articles/'all-corn-is-the-same'-and-other-foolishness-about-america's-king-crops |archive-date=December 3, 2020 |access-date=21 September 2022 |publisher=[[Ohio State University]]: College of Food, Agricultural, and Environmental Sciences}}{{cite web |last1=Nielsen |first1=R. L. |title=Corn, the Great American Crop - Corny News Network (Purdue University) |url=https://www.agry.purdue.edu/ext/corn/news/timeless/Corn.html |website=www.agry.purdue.edu |publisher=Purdue University |access-date=1 September 2026 |quote=Native Americans called their crop "maize". After seeing maize for the first time, European settlers called it "Indian corn" in an attempt to compare the crop to the small grains grown in Europe that they called "corn". Today, most of the world still refers to the crop as maize, but the U.S. simply calls it corn.}} In countries that primarily use the term ''maize'', the word ''corn'' may denote any [[cereal]] crop, varying geographically with the local [[staple food|staple]],{{OED|corn, n.1|6486816340}} such as wheat in England and oats in Scotland or Ireland. The usage of ''corn'' for maize started as a shortening of "[[Flint corn|Indian corn]]" in 18th-century North America.{{cite book |last1=Mencken |first1=H. L. |title=The American language: an inquiry into the development of English in the United States |date=1984 |publisher=[[Alfred A. Knopf]] |isbn=0-394-40075-5 |edition=4th |location=New York |page=122 |quote=Corn, in orthodox English, means grain for human consumption, especially wheat, e.g., the Corn Laws. The earliest settlers, following this usage, gave the name of Indian corn to what the Spaniards, following the Indians themselves, had called maiz. . . . But gradually the adjective fell off, and by the middle of the Eighteenth Century maize was simply called corn and grains in general were called breadstuffs. Thomas Hutchinson, discoursing to George III in 1774, used corn in this restricted sense speaking of "rye and corn mixed." "What corn?" asked George. "Indian corn," explained Hutchinson, "or as it is called in authors, maize."}}
The historian of food Betty Fussell writes in an article on the history of the word ''corn'' in North America that "[t]o say the word ''corn'' is to plunge into the tragi-farcical mistranslations of language and history".{{cite journal |last1=Fussell |first1=Betty |date=1999 |title=Translating Maize into Corn: The Transformation of America's Native Grain |journal=Social Research |volume=66 |issue=1 |pages=41–65 |jstor=40971301 |id={{Gale|A54668866}} {{ProQuest|209670587}} |quote=To say the word "corn" is to plunge into the tragi-farcical mistranslations of language and history. If only the British had followed Columbus in phoneticizing the Taino word mahiz, which the Arawaks named their staple grain, we wouldn't be in the same linguistic pickle we're in today, where I have to explain to someone every year that when Biblical Ruth "stood in tears amid the alien corn" she was standing in a wheat field. But it was a near thing even with the Spaniards, when we read in Columbus' Journals that the grain "which the Indians called maiz... the Spanish called panizo.' The Spanish term was generic for the cereal grains they knew - wheat, millet, barley, oats - as was the Italian term polenta, from Latin pub. As was the English term "corn", which covered grains of all kinds, including grains of salt, as in "corned beef".
French linguistic imperialism, by way of a Parisian botanist in 1536, provided the term Turcicum frumentum, which the British quickly translated into "Turkey wheat", "Turkey corn", and "Indian corn". By Turkey or Indian, they meant not a place but a condition, a savage rather than a civilized grain, with which the Turks concurred, calling it kukuruz, meaning barbaric.}} Similar to the British usage, the Spanish referred to maize as {{lang|es|panizo}}, a generic term for cereal grains, as did Italians with the term {{lang|it|polenta}}. The British later referred to maize as Turkey wheat, Turkey corn, or Indian corn; Fussell comments that "they meant not a place but a condition, a savage rather than a civilized grain".
International groups such as the [[Centre for Agriculture and Bioscience International]] consider ''maize'' the preferred common name.{{cite journal |date=2019 |title=''Zea mays'' (maize) |url=https://www.cabi.org/isc/datasheet/57417 |journal=CABI Compendium |publisher=[[Centre for Agriculture and Bioscience International]] |volume=CABI Compendium |doi=10.1079/cabicompendium.57417 |url-access=subscription |access-date=16 September 2022}} The word ''maize'' is used by the UN's [[Food and Agriculture Organization]],{{cite web |title=Maize |url=https://www.fao.org/land-water/databases-and-software/crop-information/maize/en/ |access-date=16 September 2022 |publisher=[[Food and Agriculture Organization]]}} and in the names of the [[International Maize and Wheat Improvement Center]] of Mexico, the Indian Institute of Maize Research,{{cite web |title=Overview – ICAR-Indian Institute of Maize Research |url=https://iimr.icar.gov.in/overview/ |archive-url=https://web.archive.org/web/20221005162737/https://iimr.icar.gov.in/overview/ |archive-date=October 5, 2022 |access-date=16 September 2022}} the Maize Association of Australia,{{cite web |title=Maize Association - Maize Association Australia |url=https://www.maizeaustralia.com.au/ |access-date=16 September 2022}} the National Maize Association of Nigeria,{{cite web |title=The Maize Association of Nigeria honors IITA for supporting the nation's agriculture |url=https://www.iita.org/news-item/the-maize-association-of-nigeria-honors-iita-for-supporting-the-nations-agriculture/ |access-date=16 September 2022 |publisher=[[International Institute of Tropical Agriculture]]}} the National Maize Association of Ghana,{{cite web |date=18 March 2016 |title=SARD-SC Maize component supports the launch of the Ghana Maize Association |url=http://bulletin.iita.org/sard-sc-maize-component-supports-the-launch-of-the-ghana-maize-association/ |access-date=10 March 2024 |publisher=[[International Institute of Tropical Agriculture]]}} the Maize Trust of South Africa,{{cite web |last1=Du Plessis |first1=Leon |title=THE MAIZE TRUST: Custodian of the maize industry |url=https://www.grainsa.co.za/the-maize-trust:-custodian-of-the-maize-industry |access-date=10 March 2024 |publisher=Grain SA}} and the Zimbabwe Seed Maize Association.{{cite journal |last1=Rusike |first1=Joseph |last2=Donovan |first2=Philip A |date=1995 |title=The maize seed industry in Zimbabwe |journal=Development Southern Africa |volume=12 |issue=2 |pages=189–196 |doi=10.1080/03768359508439804 |issn=0376-835X}} In the United States, ''maize'' can be used interchangeably with the term ''corn''.{{cite web |last1=Allen |first1=Guy H. |title=U.S. Grains – Commodity Overview, Production Cycles and Descriptions |url=https://grains.org/wp-content/uploads/2018/02/Updated-Complete-Importer-Manual.pdf |publisher=U.S. Grains Council |quote=Maize (which in the U.S. is interchangeably referred to as corn) is indigenous to the Americas. |access-date=31 August 2026}}
== Cultivation ==
=== Pre-Columbian development ===
[[File:Museo Nacional de Antropología - MAÍZ.jpg|thumb|Ancient Mesoamerican relief sculpture of maize, [[National Museum of Anthropology (Mexico)|National Museum of Anthropology of Mexico]] ]]
Maize [[cultigen|requires human intervention]] for its propagation. The kernels of its naturally-propagating [[teosinte]] ancestor fall off the cob on their own, while those of [[domesticated]] maize do not.{{cite journal |last=Benz |first=B. F. |year=2001 |title=Archaeological evidence of teosinte domestication from Guilá Naquitz, Oaxaca |journal=[[Proceedings of the National Academy of Sciences]] |volume=98 |issue=4 |pages=2104–2106 |bibcode=2001PNAS...98.2104B |doi=10.1073/pnas.98.4.2104 |issn=0027-8424 |pmc=29389 |pmid=11172083 |doi-access=free}} All maize arose from a single domestication in southern Mexico about 9,000 years ago. The oldest surviving maize types are those of the Mexican highlands. Maize spread from this region to the lowlands and over the Americas along two major paths. The centre of domestication was most likely the [[Balsas River]] valley of south-central Mexico.{{cite journal |last1=Piperno |first1=Dolores R. |date=October 2011 |title=The Origins of Plant Cultivation and Domestication in the New World Tropics: Patterns, Process, and New Developments |journal=Current Anthropology |volume=52 |issue=S4 |pages=S453–S470 |doi=10.1086/659998 |s2cid=83061925 |quote=Recent studies in the Central Balsas River Valley of Mexico, maize's postulated cradle of origin, document the presence of maize phytoliths and starch grains at 8700 BP, the earliest date recorded for the crop (Piperno et al. 2009; Ranere et al. 2009). A large corpus of data indicates that it was dispersed into lower Central America by 7600 BP and had moved into the inter-Andean valleys of Colombia between 7000 and 6000 BP. Given the number of Cauca Valley, Colombia, sites that demonstrate early maize, it is likely that the inter-Andean valleys were a major dispersal route for the crop after it entered South America |doi-access=free}} Maize reached highland Ecuador at least 8000 years ago.{{cite journal |last1=Pagán-Jiménez |first1=Jaime R. |last2=Guachamín-Tello |first2=Ana M. |last3=Romero-Bastidas |first3=Martha E. |last4=Constantine-Castro |first4=Angelo R. |date=June 2016 |title=Late ninth millennium B.P. use of ''Zea mays'' L. at Cubilán area, highland Ecuador, revealed by ancient starches |journal=[[Quaternary International]] |volume=404 |pages=137–155 |bibcode=2016QuInt.404..137P |doi=10.1016/j.quaint.2015.08.025}} It reached lower Central America by 7,600 years ago, and the valleys of the Colombian [[Andes]] between 7,000 and 6,000 years ago.
The earliest maize plants grew a single, small ear per plant. The [[Olmec]] and [[Maya peoples|Maya]] cultivated maize in numerous varieties throughout [[Mesoamerica]]; they cooked, ground and processed it through [[nixtamalization]]. By 3000 years ago, maize was central to Olmec culture, including their calendar, language, and myths.
The [[Mapuche]] people of [[Zona Sur|south-central Chile]] cultivated maize along with [[quinoa]] and [[potatoes]] in [[Pre-Columbian era|pre-Hispanic]] times.{{cite journal |last1=Dillehay |first1=Tom D. |author-link=Tom Dillehay |last2=Pino Quivira |first2=Mario |author-link2=Mario Pino Quivira |last3=Bonzani |first3=Renée |last4=Silva |first4=Claudia |last5=Wallner |first5=Johannes |last6=Le Quesne |first6=Carlos |year=2007 |title=Cultivated wetlands and emerging complexity in south-central Chile and long distance effects of climate change |url=http://www.dendrocronologia.cl/pubs/2007_Dillehay(AncientCultivatedWetlands).pdf |journal=[[Antiquity (journal)|Antiquity]] |volume=81 |issue=314 |pages=949–960 |doi=10.1017/s0003598x00096034 |s2cid=59480757}} Before the expansion of the [[Inca Empire]], maize was traded and transported as far south as 40° S in Melinquina, [[Lácar Department]], Argentina, probably brought across the Andes from Chile.{{cite journal |last1=Pérez |first1=Alberto E. |last2=Erra |first2=Georgina |date=2011 |title=Identificación de maiz de vasijas recuperadas de la Patagonia noroccidental argentina |trans-title=Identifying maize residues in pottery vessels in northwestern Patagonia, Argentina |journal=[[Magallania]] |language=es |volume=39 |issue=2 |pages=309–316 |doi=10.4067/S0718-22442011000200022 |hdl=11336/42613 |doi-access=free |hdl-access=free}}
=== Columbian exchange ===
{{further|Columbian exchange}}
[[File:The Florentine Codex- Agriculture.tiff|thumb|upright=0.8|Cultivation of maize, illustrated in the 16th-century ''[[Florentine Codex]]'' ]]
After the arrival of Europeans in 1492, Spanish settlers consumed maize, and explorers and traders [[Columbian Exchange|carried it back to Europe]]. Spanish settlers much preferred [[wheat]] bread to maize. Maize flour could not be substituted for wheat for communion bread, since in [[Christianity|Christian]] belief at that time only wheat could undergo [[transubstantiation]] and be transformed into the body of Christ.{{cite book |last=Earle |first=Rebecca |author-link=Rebecca Earle |title=The Body of the Conquistador: Food, Race, and the Colonial Experience in Spanish America, 1492–1700 |publisher=[[Cambridge University Press]] |year=2012 |pages=17, 144, 151}}
Maize spread to the rest of the world because of its ability to grow in diverse climates. It was cultivated in Spain just a few decades after Columbus's voyages and then spread to Italy, [[West Africa]], the [[Philippines]] and elsewhere.{{cite journal |last1=Salazar |first1=A.M. |last2=Pascual |first2=C.B. |last3=Caasi-Lit |first3=M.T. |last4=Pentecostes |first4=K.Z. |last5=Dumalag |first5=P.Y. |last6=Ladia |first6=V.A., Jr. |last7=Paril |first7=J.F. |date=2016 |title=Breeding Potential of Philippine Traditional Maize Varieties |url=https://sabraojournal.org/wp-content/uploads/2018/01/SABRAO-J-Breed-Genet-48-2-154-161-Salazar-1.pdf |journal=SABRAO Journal of Breeding and Genetics |volume=48 |issue=2 |pages=154–161}} By the 17th century, it was a common peasant food in Southern Europe. By the 18th century, it was the chief food of the southern French and Italian peasantry, especially as [[polenta]] in Italy.{{cite journal |last=Langer |first=William L. |year=1975 |title=American Foods and Europe's Population Growth 1750–1850 |journal=[[Journal of Social History]] |volume=8 |issue=2 |pages=51–66 |doi=10.1353/jsh/8.2.51 |jstor=3786266}}
When maize was introduced into Western farming systems, it was welcomed for its productivity. However, a widespread problem of malnutrition soon arose wherever it had become a [[staple food]].{{cite web |date=December 2001 |title=The origins of maize: the puzzle of pellagra |url=http://www.eufic.org/web/article.asp?cust=1&lng=en&sid=4&did=16&artid=103 |archive-url=https://web.archive.org/web/20060927074332/http://www.eufic.org/web/article.asp?cust=1&lng=en&sid=4&did=16&artid=103 |archive-date=September 27, 2006 |access-date=September 14, 2006 |work=Understanding Food |publisher=The European Food Information Council}} Indigenous Americans had learned to soak maize in [[alkali]]-water{{snd}}made with ashes and [[calcium oxide|lime]]{{snd}}since at least 1200–1500 BC, creating the process of [[nixtamalization]]. They did this to liberate the corn hulls, but coincidentally it also liberated the B-vitamin [[Niacin (nutrient)|niacin]], the lack of which caused [[pellagra]].{{cite book |last1=Staller |first1=John |url={{google books |plainurl=y |id=FJrr9i6HRp0C|page=317}} |title=Pre-Columbian Foodways: Interdisciplinary Approaches to Food, Culture, and Markets in Ancient Mesoamerica |last2=Carrasco |first2=Michael |date=24 November 2009 |publisher=[[Springer Science & Business Media]] |isbn=978-1-4419-0471-3 |page=317}} Once alkali processing and dietary variety were understood and applied, pellagra disappeared in the developed world. The development of high-[[lysine]] maize and the promotion of a more balanced diet have contributed to its demise. Pellagra still exists in food-poor areas and refugee camps where people survive on donated maize.{{cite book |last1=Thompson |first1=Janice J. |title=The Science of Nutrition |last2=Manore |first2=Melinda |last3=Vaughan |first3=Linda |date=15 January 2016 |publisher=[[Pearson Education]] |isbn=978-0-13-429880-1 |pages=292–321 |chapter=Nutrients involved in energy metabolism |chapter-url={{google books |plainurl=y |id=pbd5CwAAQBAJ |page=292}}}}
=== Conventional breeding ===
Maize breeding in prehistory resulted in large plants producing large ears. Modern [[plant breeding|breeding]] began with individuals who selected highly productive varieties in their fields and then sold seed to other farmers. James L. Reid was one of the earliest and most successful, developing Reid's Yellow Dent in the 1860s. These early efforts were based on [[Selection methods in plant breeding based on mode of reproduction|mass selection]] (a row of plants is grown from seeds of one parent), and the choosing of plants after pollination (which means that only the female parents are known). Later breeding efforts included ear to row selection (C. G. Hopkins c. 1896), hybrids made from selected [[inbred]] lines (G. H. Shull, 1909), and the highly successful [[double cross hybrid]]s using four inbred lines ([[Donald F. Jones|D. F. Jones]] c. 1918, 1922). University-supported breeding programs were especially important in developing and introducing modern hybrids.{{cite book |last1=Jugenheimer |first1=Robert W. |title=Hybrid Maize Breeding and Seed Production |date=1958 |publisher=[[Food and Agriculture Organization]] |location=Rome |chapter=Agricultural Development Paper #62}}
Since the 1940s, the best strains of maize have been first-generation hybrids made from inbred strains that have been optimized for specific traits, such as yield, nutrition, drought, pest and disease tolerance. Both conventional cross-breeding and genetic engineering have succeeded in increasing output and reducing the need for cropland, pesticides, water and fertilizer. There is conflicting evidence to support the hypothesis that maize yield potential has increased over the past few decades. This suggests that changes in yield potential are associated with leaf angle, lodging resistance, tolerance of high plant density, disease/pest tolerance, and other agronomic traits rather than increase of yield potential per individual plant.{{cite journal |last1=Duvick |first1=D. N. |last2=Cassman |first2=K. G. |title=Post-green-revolution trends in yield potential of temperate maize in the north-central United States |journal=[[Crop Science (journal)|Crop Science]] |volume=39 |pages=1622–1630 |year=2009 |url=http://crop.scijournals.org/cgi/content/abstract/39/6/1622 |issue=6 |s2cid=39657597 |archive-url=https://web.archive.org/web/20091115003659/http://crop.scijournals.org/cgi/content/abstract/39/6/1622 |archive-date=November 15, 2009 |doi=10.2135/cropsci1999.3961622x|url-access=subscription }}
Certain varieties of maize have been bred to produce many ears; these are the source of the "[[baby corn]]" used as a vegetable in [[Asian cuisine]].{{Cite book |last=Maiti |first=Ratikanta |url=https://books.google.com/books?id=8_m7aIfR7xEC&pg=PA52 |title=Crop Plant Anatomy |date=2012 |publisher=CABI |isbn=978-1-78064-174-4 |page=52}}{{cite journal |last1=Lopes |first1=Adelmary Prestes |last2=Nóbrega |first2=Lucia Helene Pereira |last3=Pacheco |first3=Fabio Palczewski |last4=Cruz-Silva |first4=Claudia Tatiana Araujo da |title=Maize varieties for baby corn yield and post-harvest quality under organic cropping |journal=Bioscience Journal |volume=32 |issue=2 |date=2016 |doi=10.14393/BJ-v32n2a2016-26230 |pages=298–307}} A fast-flowering variety named mini-maize was developed to aid scientific research, as multiple generations can be obtained in a single year.{{Cite journal |last1=McCaw |first1=Morgan E |last2=Wallace |first2=Jason G |last3=Albert |first3=Patrice S |last4=Buckler |first4=Edward S |last5=Birchler |first5=James A |date=2016-09-01 |title=Fast-Flowering Mini-Maize: Seed to Seed in 60 Days |journal=Genetics |volume=204 |issue=1 |pages=35–42 |doi=10.1534/genetics.116.191726 |issn=1943-2631 |pmc=5012399 |pmid=27440866}} One strain called olotón has evolved a symbiotic relationship with [[Nitrogen fixation|nitrogen-fixing]] microbes, which provides the plant with 29%–82% of its nitrogen.{{cite journal |doi=10.1371/journal.pbio.2006352 |title=Nitrogen fixation in a landrace of maize is supported by a mucilage-associated diazotrophic microbiota |year=2018 |last1=Van Deynze |first1=Allen |last2=Zamora |first2=Pablo |last3=Delaux |first3=Pierre-Marc |last4=Heitmann |first4=Cristobal |last5=Jayaraman |first5=Dhileepkumar |display-authors=etal |journal=PLOS Biology |volume=16 |issue=8 |article-number=e2006352 |pmid=30086128 |pmc=6080747 |doi-access=free }} The [[International Maize and Wheat Improvement Center]] (CIMMYT) operates a conventional breeding program to provide optimized strains. The program began in the 1980s.{{cite web |url=https://www.cimmyt.org/about/ |title=About us |publisher=[[International Maize and Wheat Improvement Center|CIMMYT]] |access-date=12 March 2024}} Hybrid seeds are distributed in Africa by its Drought Tolerant Maize for Africa project.{{cite web |title=Drought Tolerant Maize for Africa (DTMA) |date=June 17, 2022 |url=https://www.cimmyt.org/projects/drought-tolerant-maize-for-africa-dtma/ |publisher=CIMMYT |access-date=12 March 2024}}
Tropical [[landrace]]s remain an important and underused source of resistance alleles – both those [[plant disease resistance|for disease]] and [[plant defense against herbivory|for herbivores]]. Such alleles can then be [[introgressed]] into productive varieties. Rare alleles for this purpose were discovered by Dao and Sood, both in 2014.{{cite journal |last1=Chakradhar |first1=Thammineni |last2=Hindu |first2=Vemuri |last3=Reddy |first3=Palakolanu Sudhakar |title=Genomic-based-breeding tools for tropical maize improvement |journal=Genetica |date=December 2017 |volume=145 |issue=6 |pages=525–539 |doi=10.1007/s10709-017-9981-y |pmid=28875394 |s2cid=24074330 |url=http://oar.icrisat.org/10349/1/10.1007%252Fs10709-017-9981-y.pdf }} In 2018, Zerka Rashid of CIMMYT used its [[association mapping]] panel, developed for tropical drought tolerance traits. to find new [[genome|genomic]] regions providing [[sorghum downy mildew resistance]], and to further characterize known [[differentially methylated region]]s.{{cite journal |last1=Rashid |first1=Zerka |last2=Singh |first2=Pradeep Kumar |last3=Vemuri |first3=Hindu |last4=Zaidi |first4=Pervez Haider |last5=Prasanna |first5=Boddupalli Maruthi |last6=Nair |first6=Sudha Krishnan |title=Genome-wide association study in Asia-adapted tropical maize reveals novel and explored genomic regions for sorghum downy mildew resistance |journal=Scientific Reports |volume=8 |issue=1 |date=2018-01-10 |page=366 |issn=2045-2322 |pmid=29321632 |pmc=5762920 |doi=10.1038/s41598-017-18690-3 |doi-access=free|bibcode=2018NatSR...8..366R }}
=== Genetic engineering ===
{{Main|Transgenic maize}}
[[Genetically modified maize]] was one of the 26 [[genetically engineered food]] crops grown commercially in 2016.{{Cite web |url=http://www.isaaa.org/resources/publications/briefs/52/executivesummary/default.asp |title=Global Status of Commercialized Biotech/GM Crops: 2016 – ISAAA Brief 52-2016 |last=James |first=Clive |date=2016 |publisher=ISAAA |archive-url=https://web.archive.org/web/20170504055752/http://www.isaaa.org/resources/publications/briefs/52/executivesummary/default.asp|archive-date=2017-05-04|access-date=2017-08-26}}[http://www.isaaa.org/resources/publications/briefs/43/executivesummary/default.asp ISAAA Brief 43-2011]: Executive Summary, retrieved September 9, 2012 The vast majority of this is [[Bt maize]]. Genetically modified maize has been grown since 1997 in the United States and Canada; by 2016, 92% of the U.S. maize crop was genetically modified. As of 2011, herbicide-tolerant maize and insect-resistant maize varieties were each grown in over 20 countries.{{cite web |url=http://www.isaaa.org/resources/publications/pocketk/2/default.asp |title=ISAAA Pocket K No. 2: Plant Products of Biotechnology, 2018 |access-date=January 9, 2024 |url-status=live |archive-date=January 30, 2023 |archive-url=https://web.archive.org/web/20230130235541/https://www.isaaa.org/resources/publications/pocketk/2/default.asp}}
In September 2000, up to $50 million worth of food products were recalled due to the presence of [[StarLink corn recall|Starlink]] genetically modified corn, which had been approved only for animal consumption.{{cite news |last=Pollack |first=Andrew |date=September 23, 2000 |url=https://www.nytimes.com/2000/09/23/business/kraft-recalls-taco-shells-with-bioengineered-corn.html |title=Kraft Recalls Taco Shells With Bioengineered Corn |newspaper=[[The New York Times]] }}
=== Growing ===
Because it is cold-intolerant, in the [[Temperate climate|temperate zones]] maize must be planted in the spring. Its [[root]] system is generally shallow, so the plant is dependent on soil moisture. As a plant that uses [[C4 carbon fixation|{{C4}} carbon fixation]], maize is a considerably more water-efficient crop than plants that use [[C3 carbon fixation|{{C3}} carbon fixation]] such as [[alfalfa]] and [[soybean]]s. Maize is most sensitive to drought at the time of silk emergence, when the flowers are ready for pollination. In the United States, a good harvest was traditionally predicted if the maize was "knee-high by the [[Independence Day (United States)|Fourth of July]]", although modern [[Hybrid (biology)|hybrids]] generally exceed this growth rate. Maize used for [[silage]] is harvested while the plant is green and the fruit immature. Sweet corn is harvested in the "milk stage", after pollination but before starch has formed, between late summer and early to mid-autumn. Field maize is left in the field until very late in the autumn to thoroughly dry the grain, and may, in fact, sometimes not be harvested until winter or even early spring. The importance of sufficient soil moisture is shown in many parts of Africa, where periodic [[drought]] regularly causes maize crop failure and consequent [[famine]]. Although it is grown mainly in wet, hot climates, it can thrive in cold, hot, dry or wet conditions, meaning that it is an extremely versatile crop.{{cite book |last=Fernandez-Armesto |first=Felipe |year=2011 |title=The World: A History |page=470 |publisher=Penguin Academics |location=London |isbn=978-0-205-75930-9}}
Maize was planted by the [[Indigenous peoples of the Americas|Native Americans]] in small hills of soil, in the [[polyculture]] system called the [[Three Sisters (agriculture)|Three Sisters]].{{Cite web |last=Hill |first=Christina Gish |date=2020-11-20 |title=Returning the 'three sisters' – corn, beans and squash – to Native American farms nourishes people, land and cultures |url=http://theconversation.com/returning-the-three-sisters-corn-beans-and-squash-to-native-american-farms-nourishes-people-land-and-cultures-149230 |access-date=2021-01-09 |website=The Conversation}} Maize provided support for [[bean]]s; the beans provided nitrogen derived from nitrogen-fixing [[rhizobia]] bacteria which live on the roots of beans and other [[legume]]s; and [[Cucurbita|squashes]] provided ground cover to stop weeds and inhibit evaporation by providing shade over the soil.{{cite book |title=1491: New Revelations of the Americas Before Columbus |edition=2nd |author-link=Charles C. Mann (writer) |first=Charles C. |last=Mann |chapter=Cotton (or Anchovies) and Maize |pages=[https://archive.org/details/149100char/page/225 225–229] |date=July 2011 |publisher=[[Vintage Books]] |isbn=978-1-4000-3205-1 |location=New York |title-link=1491: New Revelations of the Americas Before Columbus}}