|Scientific Name||Zea mays L.|
|Common Names||English: Maize (American English: corn); German: Mais; Spanish: Maíz; French: Maïs|
In recent decades, corn production has soared. In the 1970s, about 266 million tons per year were grown on 115 million hectares (287.5 million acres) worldwide, whereas in 2007, nearly 800 million metric tons of corn were harvested from about 160 million hectares (400 million acres) of land. Today, corn is grown on 180 million hectares worldwide with a production volume of approx. 1 billion tons to meet the increasing demand for corn-based animal feed and bio-ethanol as an alternative to crude-oil based gasoline. The largest corn-producing countries are the USA (35% of global production), where it is quantitatively the most important crop, followed by China and Brazil. In poorer regions of the world, a large proportion of the harvest is used for human consumption, whereas in the industrialized countries, most of the crop is fed to livestock, primarily in the form of grain. This usage has probably contributed to the expansion of corn cultivation into regions with temperate climates. Another factor has certainly been the great progress in breeding, which has produced high-yielding hybrid varieties that are well-adapted to a wide range of climatic conditions.
Corn grows best on well-drained loamy soils with ample organic matter. It requires consistently adequate soil moisture to prevent wilting. Drought will significantly reduce yields, especially if it occurs during the silking and tasseling periods. The above-mentioned rise in the productivity of corn cultivation is partly achieved through an increased plant density. In the first half of the 20th century, the kernels were generally sown in hills that were sometimes up to 1 m (39.37 inches) apart. New, earlier-maturing varieties and the use of fertilizer have brought the possibility of a more than doubling of the number of plants per hectare in the meantime. Even so, corn covers the soil much less than other cereals. Therefore, weed control is very important, the more so as corn is quite susceptible to competition for nutrients from other plants. Another problem is soil erosion: strong rain can lead to heavy losses of topsoil, even on moderate slopes.
Corn is basically a tropical grass, and it requires high insolation and warmth. An average temperature of 20 – 24 °C (68 - 75.2 °F) is optimal, and it should not sink below 14° C (57.2 °F) at night. The minimum for germination is 8°C (46.4 °F). Nevertheless, corn is cultivated on every continent except Antarctica. In the northern part of its range, it is grown mostly for silage, because it can be harvested for this purpose while still unripe.
Depending on variety and local climate, corn may need between 70 and 210 days for full development. Due to the importance of this factor for determining the suitability of available varieties for cultivation in a particular area, these are assigned a maturity rating, which has usually been defined by a so-called FAO-number, a lower number meaning earlier ripening. However, this 3-digit code (ranging from 100 to 900, for maturity group, grading within this group and kernel color) has not been used consistently in different countries in spite of international agreements, and it has even been partly abandoned by now. In areas with only a short warm season (e.g. Central Europe), only varieties with an FAO-number of up to 400 are used, as others would need a longer growth period to reach maturity than is possible before temperatures fall again in the autumn.
The phylogeny of cultivated corn, Zea mays L., is still controversial. One of the possibilities is that it might have developed from its closest wild relative, the teosinte; from another as yet unknown (or extinct) wild grass species; or as a hybrid between the two. The oldest findings of corn are from the Tehuacán valley in southern Mexico, dated to about 5000 B.C. The word “maize” derives from the Spanish „maíz“ for „maisis“ or „mahisi“, the name in the indigenous Taino language.
The extraordinary productivity of the corn plant – it has the highest potential yield of all cereal crops - is mainly determined by two factors: its large leaf area and the fact that it is (like many other grasses) a C4-plant - i.e. it uses an alternative pathway for carbon fixation that is more efficient at high temperatures than the more common C3-pathway.
The numerous subspecies of Zea mays are divided into several groups. The economically most significant of these are: dent corn (Z. mays convar. indentata), flint corn (Z. mays convar. indurata) and soft corn (Z. mays convar. amylacea). Popcorn (Z. mays convar. everta), sweet corn (Z. mays convar. saccharata), pod corn (Z. mays convar. tunicata) and waxy corn (Z. mays convar. ceratina) are locally important. Conventional, open-pollinated varieties have nowadays been replaced almost completely by hybrids, mostly of dent and flint corn. Corn was the first crop in which the heterosis effect was utilized with significant success. Recently, transgenic corn – for example varieties provided with resistance to herbicides or producing insecticidal bacterial toxins - is gaining in importance, and is profoundly changing crop protection practice.
Poaceae (syn. Gramineae).
Besides corn (Z. mays), the genus Zea includes its wild relatives, the teosintes, and a few other species. Traditionally it has been put - together with the related genus Tripsacum - into the tribe Maydeae, because all of these species share the trait of being monoecious (i.e. not having hermaphroditic, but rather separate male and female flowers) in contrast to most other grasses. This classification has since been revised, however, and they are now members of the tribe Andropogoneae within the subfamily Panicoideae, which also includes the economically important grasses Sorghum sp. and Saccharum sp. (sugar cane).
In many developing regions of the world, corn is still of the utmost importance as a staple food for large parts of the population. In Central and South America, it is used to make almost all of the cereal products that are made from wheat or rye elsewhere.
In industrialized countries, however, corn grown for human nutrition is for the most part consumed in processed form, except for traditional uses such as tortilla, popcorn, 'corn on the cob' or polenta (generally 'dent corn'). About half of the 'corn starch' produced is used in the food industry, most of it converted into sugars. 'Corn syrup' consists mainly of glucose. In recent years, it has been replaced to a considerable extent by 'high fructose corn syrup' (HFCS), which is sweeter than corn syrup because of its fructose content. HFCS is an important sweetener for soft-drinks.
An oil can be extracted from the corn germs that is valued for its cooking properties.
While much less corn is eaten by humans nowadays than historically in many places, its use as fodder for livestock has increased significantly.
Therefore, large amounts are consumed indirectly in the form of products such as beef, pork, poultry, eggs and milk. As a rule of thumb, about 25 kg (55 lbs) of corn are needed to produce 2.5 kg (5.5 lbs) of beef. Corn grain is an ideal poultry feed. For pigs, ensilaged corn-cob-mix (CCM) is - besides its nutritional value - suitable primarily because of its fibre content. In addition, considerable amounts of the by-products from corn processing, e.g. DDGS as a by-product of corn ethanol, are used in the animal-feed industry.
The usage of corn as a raw material for the production of ethanol by fermentation has increased in response to the demand for biofuel as a renewable energy source.
Corn is not only food for humans and feed for livestock, but also a material for use in several thousand industrial products. 'Corn starch' is used in the textile, chemical and pharmaceutical industries. Pulp for paper and similar products is made from the cobs and stalks. A by-product of this process is furfural, a valuable source material for the chemical industry.
Recommendation for Integrated Crop Management
The corn crop’s intrinsic characteristic as a monocot species (grass) late row-closing leaves a portion of the seedbed as bare soil, offering ideal conditions for the germination and rapid development of weeds. Furthermore, developing corn is particularly sensitive to any sort of competition that limits its supply of nutrients. In addition, soil-borne insects and diseases and sucking pests can do significant harm to germinating corn seeds, corn roots and young corn plants in their early establishment phases. Thus, it is extremely important to control pests, diseases and weeds very effectively, eradicating them completely if possible to protect the harvest.