Maize (Zea mays L.) is the leading grain in the world with an annual production of more than 1 billion tons in 2013, and it constitutes staple foods for large groups of people in Latin America, Africa, and Asia. Maize production has increased the most because of its greater adaptation to different ecological systems and strong demand for bioethanol and animal feed and for the production of sweeteners and other nonfood industrial products (i.e., biodegradable packaging materials).
The genetic modification of maize (Bt maize) is partially responsible for record productions observed in the past 10 years. According to the FAO, 54%, 19%, 13.8%, and 14% were used for feed, food manufacture, direct food, and bioethanol, respectively.
Corn: The Edible Grain
Corn, (Zea mays), also called Indian corn or maize, cereal plant of the grass family (Poaceae) and its edible grain. The domesticated crop originated in the Americas and is one of the most widely distributed of the world’s food crops. Corn is used as livestock feed, as human food, biofuel, and as raw material in the industry.
Maize is used for the production of numerous indigenous foods, maize meals, flours, grits, starches, sweeteners, cooking oils, bread, tortillas, breakfast foods, snacks, bioethanol, and alcoholic beverages. Processed maize products are manufactured from raw materials obtained from three major industries: dry milling, wet milling, and nixtamalization
Maize plants contain both male and female reproductive structures and reproduce by both cross-pollination and self-pollination. In most commercially viable maize genotypes, the female structure (the ear) projects outward from a central stalk, while the male structure (the tassel) projects out the top of the stalk. Pollen from the tassel is carried by the wind to other maize plants, where fertilization of the individual kernels on the ear occurs. The ears of maize may range in size from about 2.5 to over 45 cm long. The kernel size, shape, and color also vary widely.
- Kingdom: Plantae
- Clade: Tracheophytes
- Clade: Angiosperms
- Clade: Monocots
- Clade: Commelinids
- Order: Poales
- Family: Poaceae
- Subfamily: Panicoideae
- Genus: Zea
- Species: Z. mays
Domestication and History
Corn was first domesticated by native peoples in southern Mexico about 10,000 years ago. Modern corn is believed to have been derived from the Balsas teosinte (Zea mays parviglumis), a wild grass. Its culture had spread as far north as southern Maine by the time of European settlement of North America, and Native Americans taught European colonists to grow the indigenous grains. Since its introduction into Europe by Christopher Columbus and other explorers and colonizers, corn has spread to all areas of the world suitable for its cultivation. It is grown from 58° N latitude in Canada and Russia to 40° S latitude in South America, with a corn crop maturing somewhere in the world nearly every month of the year. It is the most important crop in the United States and is a staple food in many places.
Origin and Evolution
Maize is the domesticated variant of teosinte. The two plants have dissimilar appearances, maize having a single tall stalk with multiple leaves and teosinte being a short, bushy plant. The difference between the two is largely controlled by differences in just two genes, called grassy tillers-1 (gt1, A0A317YEZ1) and teosinte branched-1 (tb1, Q93WI2).
Several theories had been proposed about the specific origin of maize in Mesoamerica:
- It is a direct domestication of a Mexican annual teosinte, Zea mays ssp. parviglumis, native to the Balsas River valley in south-eastern Mexico, with up to 12% of its genetic material obtained from Zea mays ssp. mexicana through introgression.
- It has been derived from hybridization between small domesticated maize (a slightly changed form of a wild maize) and a teosinte of section Luxuriantes, either Z. luxurians or Z. diploperennis.
- It has undergone two or more domestications either of a wild maize or of a teosinte. (The term “teosinte” describes all species and subspecies in the genus Zea, excluding Zea mays ssp. mays.)
- It has evolved from a hybridization of Z. diploperennis by Tripsacum dactyloides.
- In the late 1930s, Paul Mangelsdorf suggested that domesticated maize was the result of a hybridization event between unknown wild maize and a species of Tripsacum, a related genus. This theory about the origin of maize has been refuted by modern genetic testing, which refutes Mangelsdorf’s model and the fourth listed above.
The teosinte origin theory was proposed by the Russian botanist Nikolai Ivanovich Vavilov in 1931 and the later American Nobel Prize-winner George Beadle in 1932. It is supported experimentally and by recent studies of the plants’ genomes. Teosinte and maize can cross-breed and produce fertile offspring.
The domestication of maize is of particular interest to researchers—archaeologists, geneticists, ethnobotanists, geographers, etc. The process is thought by some to have started 7,500 to 12,000 years ago. Research from the 1950s to 1970s originally focused on the hypothesis that maize domestication occurred in the highlands between the states of Oaxaca and Jalisco, because the oldest archaeological remains of maize known at the time were found there.
As with many plants and animals, Z. mays has a positive correlation between effective population size and the magnitude of selection pressure. Z. m. having an EPS of ~650,000, it clusters with others of about the same EPS, and has 79% of its amino acid sites under selection.
Recombination is a significant source of diversity in Z. mays. (Note that this finding supersedes previous studies which showed no such correlation.)
This recombination/diversity effect is seen throughout plants but is also found to not occur – or not as strongly – in regions of high gene density. This is likely the reason that domesticated Z. mays have not seen as much of an increase in diversity within areas of higher density as in regions of lower density, although there is more evidence in other plants.
Some lines of maize have undergone ancient polyploidy events, starting 11m years ago. Over that time ~72% of polyploid duplicated genes have been retained, which is higher than other plants with older polyploidy events. Thus maize may be due to losing more duplicate genes as time goes along, similar to the course followed by the genomes of other plants. If so – if gene loss has merely not occurred yet – that could explain the lack of observed positive selection and lower negative selection which is observed in otherwise similar plants, i.e. also naturally outcrossing and with similar effective population sizes.
Ploidy does not appear to influence EPS or the magnitude of the selection effect in maize.
The corn plant is a tall annual grass with a stout, erect, solid stem. The large narrow leaves have wavy margins and are spaced alternately on opposite sides of the stem. Staminate (male) flowers are borne on the tassel terminating the main axis of the stem. The pistillate (female) inflorescences, which mature to become the edible ears, are spikes with a thickened axis, bearing paired spikelets in longitudinal rows; each row of paired spikelets normally produces two rows of grain. Varieties of yellow and white corn are the most popular as food, though there are varieties with red, blue, pink, and black kernels, often banded, spotted, or striped. Each ear is enclosed by modified leaves called shucks or husks.
Types of Maize
Many forms of maize are used for food, sometimes classified as various subspecies related to the amount of starch each has:
- Flour corn: Zea mays var. amylacea
- Popcorn: Zea mays var. everta
- Dent corn : Zea mays var. indentata
- Flint corn: Zea mays var. indurata
- Sweet corn: Zea mays var. saccharata and Zea mays var. rugosa
- Waxy corn: Zea mays var. ceratina
- Amylomaize: Zea mays
- Pod corn: Zea mays var. tunicata Larrañaga ex A. St. Hil.
- Striped maize: Zea mays var. japonica
Although there are hundreds of ‘races’ of maize, most of the commercially grown hybrids emanated from only a few major races. For the purposes of discussing the commercial importance of maize, maize types can be subdivided into four categories not related to race.
Dent maize is the primary type of maize grown in the US Corn Belt as well as in Europe, South Africa, and China. Dent varieties have been adapted through hybridization and selection to provide a wide range of agronomic and kernel characteristics. Special dent varieties have been produced with unique starch characteristics. High-amylose (linear starch) and waxy (branched starch) maize genotypes have been grown commercially for many years. Other unique genotypes such as high-oil maize and high-lysine maize are also being produced.
Flint maize is genetically different in ancestry from dent maize and is characterized by hard, round kernels. Flint maize endosperms consist predominantly of the hard or vitreous endosperms. The hard endosperm allows flint maize to withstand greater impact forces before being damaged, which has advantages in commercial merchandizing. The agronomic characteristics of flint maize differ from dent maize, primarily due to the unique needs of the historical growing regions.
Popcorn is flint-type maize that has been genetically selected for its ability to expand or ‘pop’ when heated. Popping occurs when the kernels are rapidly heated to ∼240 °C. The dense endosperm restricts water vapor diffusion that causes pressure to build within the kernel until it explodes. It is the starch granules that explode and in the process stretch the protein matrix. As the protein matrix cools, it becomes rigid. The white fluffy part of popped popcorn is gelatinized starch splattered on the surface of the expanded cell protein matrix.
Sweetcorn is dent-type maize that is harvested while still immature for canning, freezing, and direct consumption as a vegetable. Sweetcorn hybrids contain a gene that retards the conversion of glucose to starch in the endosperm. There are generally three to four times more short-chain polysaccharides accumulated in sweetcorn than in other maize varieties.
Commercial classifications, based mainly on kernel texture, include dent corn, flint corn, flour corn, sweet corn, and popcorn. Dent corn, primarily grown as animal feed and for food manufacturing, is characterized by a depression in the crown of the kernel caused by unequal drying of the hard and soft starch making up the kernel. Flint corn, containing little soft starch, has no depression; it is used for decoration and is eaten as hominy in the Americas.
Flour corn, composed largely of soft starch, has soft, mealy, easily ground kernels and is an important source of cornflour. Sweet corn, commonly sold fresh, frozen, or canned as a vegetable, has wrinkled translucent seeds; the plant sugar is not converted to starch as in other types. Popcorn, an extreme type of flint corn characterized by small hard kernels, is devoid of soft starch, and heating causes the moisture in the cells to expand, making the kernels explode. Improvements in corn have resulted from hybridization, based on crossbreeding of superior inbred strains.
Maize is best grown in warm, tropical, and sub-tropical regions as it requires warm soils to develop optimally. One of the most important requirements for growing maize is high-quality soil that is deep, fertile and well-draining with a pH between 6.0 and 6.8. Maize plants are very heavy feeders and even the most fertile of soils may need to supplement with nutrients as the plants develop particularly nitrogen. Maize also requires plenty of space as it grows and is pollinated by wind. It should be planted where it will receive full sunlight for most of the day and provided with ample moisture.
Planting dates for maize depend on the variety being grown. Standard varieties should be planted when the soil has warmed to at least 12.7°C (55°F) and super sweet varieties when the soil reaches 18.3°C (65°F). Soil can be brought up to temperature faster by laying black plastic mulches approximately 1 week prior to planting. Seeds should be sown about 2.5 cm (1 in) deep and 10–15 cm (~3–4 in) apart allowing 76–91 cm (~30–36 in) between rows.
Maize should be planted in blocks (numerous rows) rather than in a single long row as it is wind pollinated and pollen can transfer between plants much more efficiently. Seedlings should be thinned to a final spacing of 20–30 cm (8–12 in) when they are approximately 7.5–10.0 cm (3–4 in) in height. It is common to stagger maize plantings to ensure a continuous harvest over the summer months.
Corn soil needs
The very most basic thing for growing really good crops is good soil. Soil that is not only high infertility but is alive with beneficial organisms. The ideal soil for growing corn is deep (six or more feet), medium-textured and loose, well-drained, high in water-holding capacity and organic matter, and able to supply all the nutrients the plant needs. Of course, not everyone has the perfect soil, and corn isn’t so fussy that it can’t do well on less than ideal soil. But I will show you how to build up your soil so that you can grow much better corn.
General care and maintenance
Maize plants are heavy feeders, particularly nitrogen (N) and care should be taken to provide them with adequate nutrients by applying fertilizer. Maize undergoes a rapid growth period between 30 and 40 days after planting and should be fertilized just before this. All fertilizer applications should be made before the tasseling period to ensure the plant maximizes nitrogen use.
Be aware of symptoms of nutrient deficiency, plants should be a deep green color. Purple-tinged leaves indicate that the plants are suffering from a lack of phosphorous, whereas light green leaves indicate a lack of nitrogen. Apply fertilizer. Plants also require adequate soil moisture throughout the growing period in order to tassel and form silks. Soaker hoses can be used to great effect in small to mid-size plantings. Pollination occurs when pollen is transferred from the male tassel to the female silk by the wind. Each silk produced a single kernel of corn and partially filled ears are usually a result of poor pollination.
Each maize stalk should produce 1 large ear of maize. Under ideal conditions, the stalk will produce a second, slightly smaller ear which reaches maturity slightly later than the first. Maize ears should be harvested at the “milk stage” of development when the kernels within the husk are well packed and produce a milky substance when the kernel is punctured. Check ears for ripeness by gently peeling back a small portion of the husk. Be sure to check the ears frequently for ripeness and harvest as required as ears can quickly become over-ripe and lose their sweetness. Remove the ears from the stalk by pulling quickly downward while twisting and then refrigerate until consumption.
What are the Optimal Conditions for Corn to Grow?
Though maize crops have been modified to better adapt to different weather conditions, this crop generally does not do well in cold weather. For optimal seed germination, the soil temperature should be at least 10 degrees celsius. As with the other cereals, maize needs a fair share of water to grow. However, young maize plants are sensitive to high water levels. In waterlogged fields, they generally only survive between 48 hours to four days. This kind of water stress in maize causes restrictions on the plant’s oxygen uptake.
Wet and cold weather conditions also bring about other issues. Such conditions are the ideal environment for Northern Corn Leaf Blight (NCLB). NCLB is a kind of fungal infections maize plants can suffer from and are at first usually noticed on lower leaves. At first, the site of infection has a green-grey color and is between 3-15 cm long. Over time the lesions turn to a brown color that also indicates the area of the plant has died. Though this fungus can impact the plant’s wellbeing and harvest outcomes, the actual maize cobs are unaffected.
Once the little maize sprouts have emerged, the growing season is underway. Generally, maize requires between 60 to 100 days to mature and be ready for harvest. The length of the increasing period heavily depends on the weather. As mentioned, maize does not do well in cold conditions. Hence unexpected frost may extend the growing period or even kill the plants altogether. When the crops are fully grown and their moisture levels between 23-25%, the cobs are ready to be harvested.
In the past, like all other crops, maize was harvested manually and later developed to include the use of animals such as horses for a horse-drawn sled cutter. The stalks of the maize were cut using the sled. However, the binding of the stalks for drying, picking the cobs, and husking them still remained a completely human-dependent process. The first mechanical machines were invented in the 1850s. Though maize can still be harvested manually if other equipment is unavailable, a specialized corn harvester is generally used. Among the newly invented machinery was the mechanical picker. This machine, whose much improved open versions are still around today, allows the farmer to directly and automatically pick the maize cobs from the stalks.
As temperatures remain hot for much of the state, corn continues to put on leaf collars and is approaching the start of flowering. Corn is a plant that has separate male (anthers on the tassel) and female (silks in the ear) flowers, and it is critical that the timing of flower emergence and activity overlap (sometimes referred to as the ‘nicking’ period) to ensure good pollination and kernel set. Another term used for flowering synchrony is the ‘anthesis-silking interval,’ which is the time from pollen shedding to silk emergence.
The start of pollen shed from the anthers on the tassel is called ‘anthesis’ and can occur before the plant reaches the VT growth stage. The VT growth stage is defined as “plants with all branches of the tassel fully visible, extended outward, and not held in by the upper leaves.” Many modern hybrids begin shedding pollen while the tassel is still emerging from the surrounding leaves.
Silk emergence signals the start of the R1 growth stage, which is defined as “one or more silks extending outside the husk leaves of the ear.” In many modern hybrids, we will actually see silks emerging prior to the tassel being fully emerged. This leads to a negative anthesis silking interval (silk emerges before pollen shedding), which is one way breeders have improved yields in modern hybrids. Shortening the time from anthesis to silking increases the likelihood of pollination and has helped increase yield over time.
High temperatures and low moisture levels may lengthen the anthesis-silking interval compared to normal conditions, but both anthesis and silking last for approximately six days and occur throughout the day, so poor nick is not usually a common occurrence. Planting multiple hybrids in a field that vary slightly in their relative maturity or days to flowering can also help reduce the likelihood that the nicking period is missed.
Both high temperatures and moisture can also affect pollination success. It is recognized that temperatures above 90 degrees F can cause pollen to be non-viable, but much of the pollen shed in corn occurs in the morning hours before temperatures climb to these levels. Additionally, new pollen is made each day during this phase. The longevity of the pollen shed at lower temperatures can also be affected by relative humidity. Pollen sheds from the plant with a moisture content of 50-65% and can lose viability once the moisture content drops to 30%.
In low relative humidity and high-temperature conditions, this can happen more quickly. Moisture stress can slow the rate of silk elongation as this is driven by turgor pressure. Low relative humidity in combination with high temperatures can cause silks to desiccate and can reduce pollination success, but this may not be a major issue given the silks are close to the stalk and in the middle of the canopy where relative humidity tends to be greater than outside the canopy.
Genetically Modified Corn
Many industrial and feedstock varieties of corn are genetically modified organisms (GMOs) engineered for resistance to the herbicide glyphosate or to produce proteins from Bacillus thuringiensis (Bt) to kill specific insect pests. In addition, some strains have been genetically engineered for greater drought tolerance and to increase their nutritional value. Most of the corn grown in the United States is GMO, which may reduce the need for herbicides and insecticides.
What is Bt Maize?
Bacillus thuringiensis is a species of bacteria that produces proteins that are toxic to certain insects. Because of this, it has been used as a safe microbial insecticide for over 50 years to control pest caterpillars. Bt insecticides are popular with organic farmers because they are considered “natural insecticides” and they differ from most conventional insecticides because they are toxic to only a small range of related insects.
This is because specific pH levels, enzymes, and midgut receptors are required to activate and bind a given Cry toxin to midgut cells, which leads to pore formation in the insect’s intestine and death. A “lock and key” analogy is useful to explain this specificity. If the midgut receptor is considered the “lock” and the Cry protein is the “key” then insect death only occurs when the “lock and key” match.
There are a number of Cry toxins that are categorized by their spectrum of activity. For maize pests, primary Cry proteins are Cry1 and Cry2 for Lepidoptera and Cry3 proteins for Coleoptera. Maize can be genetically engineered to produce these specific Cry toxins. As such, aspects of Bt maize are similar to host plant resistance traits such as DIMBOA (2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one), which at high levels reduces damage by European corn borer.
Seed providers often combine or stack traits for Lepidoptera and Coleoptera control into the same plant. Also, different types of Bt toxins targeted for the same insects are often combined into more effective plant protectants called pyramids. This multiple toxin approach is useful for managing insect resistance to Bt maize.
Why is Bt Maize popular with growers?
Growers are attracted to the convenience of Bt maize hybrids because they allow for “in the bag” insect protection. GE maize seed comes from the seller with innate pest resistance. Functionally, this means that growers will be handling and applying fewer chemical insecticides, which has both health benefits for the growers and important environmental benefits. It also of course means farmers can spend less time applying insecticides but still be confident in the protection of their crop from key pests.
Furthermore, growers are attracted to the yield protection and improved grain quality commonly found with Bt maize. Interestingly, due to the introduction of Bt maize, recent research suggests there has been an areawide suppression of European corn borer populations. This is beneficial to both Bt and non-Bt maize growers.
Reduced use of insecticides
Bt maize offers both economic and environmental advantages and grower responses indicate an awareness of both types of these benefits. Many growers cite unique opportunities to protect yield and reduce handling (and use) of insecticides to explain their rapid adoption of Bt maize. Brookes and Barfoot (2010) estimated that from 1996 to 2008 the cumulative decrease in insecticide active ingredient (a.i.) use on Bt maize was 35% (29.9 million kg) globally. Much of the reduction in insecticide a.i. was probably due to coleopteran-active Bt maize, as insecticides used against Diabrotica spp. comprise 25–30% of the global total in maize.
Historically, growers had difficulty controlling corn borers because insecticides are not effective after larvae have tunneled into the stalk. One entomologist called corn borers “silent thieves” because stalk tunneling and ear injury often reduced yields 5-10 percent or more with many growers not even noticing. When entomologists started to experiment with Bt maize in the early 1990s, many were astounded that the plants were near “bulletproof” to corn borer injury. Previously plant breeders were able to increase host plant resistance, but none of these plants were “bulletproof”. Not surprisingly, growers that use Bt maize often see higher yields due to this reduced insect injury.
Improved grain quality
Another benefit of Bt maize is the reduced occurrence of ear molds. Because insect damage provides a site for infection by molds, Bt-protected maize can have lower levels of toxins produced by molds (i.e., mycotoxins), especially fumonisin and deoxynivalenol. The consequences of contamination with mold may be serious, as fumonisins can cause fatal leukoencephalomalacia in horses, pulmonary edema in swine, and cancer in laboratory rats. Economic analysis suggests that USA farmers save $23 million annually through reduced mycotoxins and mycotoxin reduction also could be a significant health benefit in other parts of the world where maize is a diet staple.
Nitrogen deficiency: The typical symptom of nitrogen deficiency is the plant turns pale green; a ‘V’ shaped yellow coloration on leaves. This pattern starts from leaf end to leaf collar. The symptom begins from lower to upper leaves.
Phosphorous deficiency: The deficient plants are dark green and lower leaves show reddish-purple discoloration.
Potassium deficiency: The leaf margins turn yellow and brown which appears like firing or drying. The symptoms progress from lower leaves to upper leaves.
Sulfur deficiency: Symptom appears on younger leaves where we will see yellow color striping(interveinal chlorosis).
Zinc deficiency: Upper leaves shows broad bands of yellow coloration and later turn pale brown or gray necrosis(dead-spots). The symptom first appears in the middle of leaves and progresses outward.
- African armyworm (Spodoptera exempta)
- African sugarcane borer (Eldana saccharina)
- Common armyworm (Pseudaletia unipuncta)
- Common earwig (Forficula auricularia)
- Corn delphacid (Peregrinus maidis)
- Corn leaf aphid (Rhopalosiphum maidis)
- Corn rootworms (Diabrotica spp) including Western corn rootworm (Diabrotica virgifera virgifera LeConte), Northern corn rootworm (D. barberi or D. longicornis), and Southern corn rootworm (D. undecimpunctata howardi)
- Corn silkfly (Euxesta stigmatias)
- Asian corn borer (Ostrinia furnacalis)
- European corn borer (Ostrinia nubilalis) (ECB)
- Fall armyworm (Spodoptera frugiperda) Some sweet corn varieties have developed partial resistance to fall army worms by producing a unique 33-kD proteinase that significantly retards fall army worm growth.
- Corn earworm/Cotton bollworm (Helicoverpa zea)
- Lesser cornstalk borer (Elasmopalpus lignosellus)
- Maize weevil (Sitophilus zeamais)
- Northern armyworm, Oriental armyworm, or Rice ear-cutting caterpillar (Mythimna separata)
- Southwestern corn borer (Diatraea grandiosella)
- Stalk borer (Papaipema nebris)
The susceptibility of maize to the European corn borer and corn rootworms, and the resulting large crop losses which are estimated at a billion dollars worldwide for each pest, led to the development of transgenics expressing the Bacillus thuringiensis toxin. “Bt maize” is widely grown in the United States and has been approved for release in Europe.
- Corn smut or common smut (Ustilago maydis): a fungal disease, known in Mexico as huitlacoche, which is prized by some as a gourmet delicacy in itself
- Northern corn leaf blight (Purdue Extension site) (Pioneer site)
- Southern corn leaf blight
- Maize downy mildew (Peronosclerospora spp.)
- Maize dwarf mosaic virus
- Maize streak virus
- Stewart’s wilt (Pantoea stewartii)
- Goss’s wilt (Clavibacter michiganensis subsp. nebraskensis)
- Grey leaf spot
- Mal de Río Cuarto virus (MRCV)
- Stalk rot
- Ear rot
- Aspergillus flavus
- A. parasiticus
Maize and Remote Sensing
Like other crops, maize needs to be protected from various diseases that affect its development and yield. As mentioned above, one common illness that farmers need to watch out for is the Northern Corn Leaf Blight. Another fungal disease that farmers battle is the so-called Corn Smut. However, in Mexico, this infection is not always considered harmful. Here the infected but not yet fully developed galls of the maize are considered a delicacy and can be enjoyed as a taco filling.
Unlike the Northern Corn Leaf Blight, Corn Smut also attacks the actual maize cobs. Corn Smut prefers warmer climates and causes significant economic losses for the farmers. Early signs of this fungal infection are white-colored galls. This later burst and release fungal spores that infect other plants. The spores can even overwinter in the soil and attack plants in the spring. Unfortunately, there are no chemical means to kill or control Corn Smut. Early detection and removing infected plants is the only way of keeping the fungus in check.
However, detecting infected cobs in fast fields and doing so before the galls rupture and further, the fungus’ spread is rather challenging. Using remote sensing, even maize farmers can receive a lot of help, for instance with detecting pests and infections before they have the chance to make considerable damages to the crop and yield. Early detection of infestations, even before they are visible to the human eye, is essential especially for infections that cannot be managed using chemical assistance. Monitoring maize health is not the only assistance farmers can get from remote sensing. Remote sensing can even help farmers to optimize their sowing strategies by suggesting the best sowing dates.
Difference Between Corn And Maize
The word “corn” has various meanings depending upon different geographical regions. It stands for any local grains that are safe to eat and harvested in large areas. In British English, the word corn pertains to any cereal crop or grain. Etymologically, the Latinate word “grain” and the Germanic word “corn” represent any edible plant seed like millet, barley, rye, wheat, maize, oats, etc.
For the British people, corn is the chief grain that is available in their county as a food crop; so they interpreted corn as wheat. When the English and German speakers entered the New World, they attributed the term corn to the local grain namely, “Zea mays”. At the same time, they distinguished Zea mays as Indian corn, to keep the word “corn” separate so as to apply it for the grains in total.
In many countries, corn is the name given to the leading crop grown in certain districts. In Scotland and Ireland, it relates to oats. In the Bible, corn is nothing but wheat and barley. In the USA and Canada, corn and maize are one and the same and are meant for the plant that produces kernels used for cooking. However, the term corn is preferred over maize for food products that are made from it, such as corn flour, corn starch, cornmeal, etc.
However, with regard to commodity trading, corn is only maize and does not include any other grains. In culinary, the corn is generally mentioned as sweet corn, popcorn, cornflakes, baby corn, dent corn, flint corn, flour corn, and waxy corn. It is the main component of canned corn, baby food, mush, puddings, and many other human foods.
A more simple way to distinguish the two terms is to look at how they are used in reference to the maturity of the grain. Maize is used to referring to the food crop, especially prior to harvesting. A farmer is growing maize, and will eventually harvest maize to sell on the market as corn. Maize can refer to what is grown in the field, whereas corn refers to the harvested product, or the food at the market or on your dinner plate.
Another easy way to think about the differences between the two terms is this: All maize is corn, but not all corn is maize. Depending on where you are, corn can reference a variety of different grains, but maize is always referring to the same crop, which we commonly call corn.
When corn is being discussed in a technical or scientific setting, the word maize is used instead of the less precise and more general term corn. In the study of genetics, for example, corn is always referred to as maize. In America, Australia, and New Zealand, corn can be used in reference to the plant that cobs grow on, the individual kernels that are found on the cob of the popular crop, and the cob itself. Yes, you read that correctly, corn produces ears of corn. Corn is indeed corn, both on the cob, and off.
As if the difference between corn and maize wasn’t confusing enough on its own, there are also corn mazes. Corn mazes are intricate and confusing pathways cut into a field of corn for entertainment purposes. Corn farmers create corn mazes to increase revenue and entice people to visit and spend money at their corn farms. Corn mazes can be found all over the world, usually in autumn around Halloween. In the UK, they are called maize mazes, which is hilarious, and at the same time, also makes perfect sense.
When maize was first introduced into farming systems other than those used by traditional native-American peoples, it was generally welcomed with enthusiasm for its productivity. However, a widespread problem of malnutrition soon arose wherever maize was introduced as a staple food. This was a mystery since these types of malnutrition were not normally seen among the indigenous Americans, for whom maize was the principal staple food.
It was eventually discovered that the indigenous Americans had learned to soak maize in alkali — water (the process now known as nixtamalization) — made with ashes and lime (calcium oxide) since at least 1200–1500 BC by Mesoamericans. They did this to liberate the corn hulls, but (unbeknownst to natives or colonists) it coincidentally liberates the B-vitamin niacin, the lack of which was the underlying cause of the condition known as pellagra.
Maize was introduced into the diet of non-indigenous Americans without the necessary cultural knowledge acquired over thousands of years in the Americas. In the late 19th century, pellagra reached epidemic proportions in parts of the southern US, as medical researchers debated two theories for its origin: the deficiency theory (which was eventually shown to be true) said that pellagra was due to a deficiency of some nutrient, and the germ theory said that pellagra was caused by a germ transmitted by stable flies. A third theory, promoted by the eugenicist Charles Davenport, held that people only contracted pellagra if they were susceptible to it due to certain “constitutional, inheritable” traits of the affected individual.
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 also contributed to its demise. Pellagra still exists today in food-poor areas and refugee camps where people survive on donated maize.
Maize contains lipid transfer protein, an indigestible protein that survives cooking. This protein has been linked to a rare and understudied allergy to maize in humans. The allergic reaction can cause skin rash, swelling or itching of mucous membranes, diarrhea, vomiting, asthma, and, in severe cases, anaphylaxis. It is unclear how common this allergy is in the general population.
Fungicide application does not reduce fungal growth or mycotoxin dramatically, although it can be a part of a successful reduction strategy. Among the most common toxins are those produced by Aspergillus and Fusarium spp. The most common toxins are aflatoxins, fumonisins, zearalenone, and ochratoxin A. Bt maize discourages insect vectors and by so doing it dramatically reduces concentrations of fumonisins, significantly reduces aflatoxins, but only mildly reduces others.
Uses and Products
Corn is one of the world’s most productive and dominant crops. It is grown extensively as food for both humans and livestock, as a biofuel, and as a crude material in the industry.
Food and nutrition
Corn is the third-largest plant-based food source in the world. Despite its importance as a major food in many parts of the world, corn is inferior to other cereals in nutritional value. Its protein is of poor quality, and it is deficient in niacin. Diets in which it predominates often result in pellagra (niacin-deficiency disease). Corn is high in dietary fibre and rich in antioxidants.
Unlike many other cereal grains, corn flour is gluten-free and cannot be used alone to make rising breads. It is widely used, however, in Latin American cuisine to make masa, a kind of dough used in such staple foods as tortillas, arepas, and tamales. In the United States and many other places, sweet corn is boiled or roasted on the cob, creamed, converted into hominy (hulled kernels) or meal, and cooked in corn puddings, mush, polenta, griddle cakes, cornbread, and scrapple. It is also used for popcorn, confections, and various manufactured breakfast cereal preparations.
Corn oil, valued for its bland flavor and light color, is used primarily for food. It is favored as a salad oil and frying oil because it contains little cholesterol. Corn oil can be converted into margarine by hydrogenation, a process in which the oil is combined with hydrogen at high temperature and pressure in the presence of a catalyst.
Corn is also fermented into a number of alcoholic beverages, notably bourbon and other corn whiskeys.
Corn is also used to produce ethanol (ethyl alcohol), a first-generation liquid biofuel. In the United States, corn ethanol is typically blended with gasoline to produce “gasohol,” an automotive fuel that is 10 percent ethanol. Although corn-based biofuels were initially touted as environmentally friendly alternatives to petroleum, their production diverts arable land and feedstock from the human food chain, sparking a “food versus fuel” debate.
In addition, crops grown for biofuel can compete for the world’s natural habitats, and the emphasis on ethanol derived from corn has shifted grasslands and brushlands to corn monocultures in some places, impacting biodiversity. Beyond land-use changes, the process of growing corn to produce ethanol consumes fossil fuels in farming equipment, fertilizer manufacturing, corn transportation, and ethanol distillation.
In this respect, ethanol made from corn represents a relatively small energy gain; the energy gain from sugarcane is greater and that from cellulosic ethanol (made from nonedible plant parts such as agriculture waste) or algae biodiesel could be even greater, though the conversion technology is generally less efficient than that of first-generation biofuels.
Industrial and other applications
Many parts of the corn plant are used in industry, and several types of corn are grown primarily for their industrial applications. Corn grain is processed by wet milling, in which the grain is soaked in a dilute solution of sulfurous acid; by dry milling, in which the corn is exposed to a water spray or steam; and by fermentation, in which starches are changed to sugars and yeast is employed to convert the sugars into alcohol.
Cornstarch (made from wet-milled corn) can be broken down into corn syrup, a common sweetener that is generally less expensive than sucrose. Corn syrup is sold commercially as either light or dark corn syrup. Light corn syrup has been clarified and decolorized; it is used in baked goods, jams and jellies, and many other food products. Because it does not crystallize when heated, it is particularly valued as an ingredient in candies.
Dark corn syrup is made by combining corn syrup with molasses and caramel coloring and is sweeter than light corn syrup. Dark corn syrup is used in the same ways as light; it is also used as a table syrup. Corn syrup can be further processed into high-fructose corn syrup, which is used extensively in processed foods such as soft drinks and candies.
In addition to its edible uses, corn oil has been incorporated into soaps, paints, and inks. It also has been used in the production of certain insecticides and in the manufacture of biodiesel. The oil cake remaining after solvent extraction is ground and used as an animal fodder known as hominy feed.
Corn stalks are made into paper and wallboard; husks are used as filling material; cobs are used directly for fuel, to make charcoal, and in the preparation of industrial solvents.
Corn husks also have a long history of use in the folk arts for objects such as woven amulets and corn husk dolls. In the United States, the colorful variegated strains known as Indian corn are traditionally used in autumn harvest decorations.
Source: 1. Britannica, Difference Between, Plant Village, Vultus, Gardening Channel, Ag Crops The Ohio State University, Eco-Farming Daily, Wikipedia
2. Pellegrino, E., Bedini, S., Nuti, M. et al. Impact of genetically engineered maize on agronomic, environmental and toxicological traits: a meta-analysis of 21 years of field data. Sci Rep 8, 3113 (2018). https://doi.org/10.1038/s41598-018-21284-2
3. Encyclopedia of Food Sciences and Nutrition (Second Edition)
4. Encyclopedia of Food and Health 2016, Pages 601-609