The term "maize" derives from the Spanish form of the indigenous Taino word maiz for the plant. This was the term used in the United Kingdom and Ireland, where it is now usually called "sweet corn", the most common form of the plant known to people there. Sweet corn is harvested earlier and eaten as a vegetable rather than a grain. Outside the British Isles, another common term for maize is "corn". This was originally the English term for any cereal crop. In North America, its meaning has been restricted since the 19th century to maize, as it was shortened from "Indian corn". The term Indian corn now refers specifically to multi-colored "field corn" (flint corn) cultivars.
In scientific and formal usage, "maize" is normally used in a global context. Equally, in bulk-trading contexts, "corn" is used most frequently. In the UK, Australia and other English-speaking countries, the word "corn" is often used in culinary contexts, particularly in naming products such as popcorn, corn flakes and baby corn. However, within the United States, the term "maize" is almost totally unheard of. "Maize" is used in agricultural and scientific references.
In Southern Africa, maize is commonly referred to as mielie or mealie, from the Portuguese milho. Mielie-meal is the ground form. Corn is very popular in the Coastal Plains.
Exotic varieties of maize are collected to add genetic diversity when selectively breeding new domestic strains.
Variegated maize ears Many forms of maize are used for food, sometimes classified as various subspecies related to the amount of starch each had:
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
Because it is cold-intolerant, in the 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 C4 plant (a plant that uses C4 carbon fixation), maize is a considerably more water-efficient crop than C3 plants (plants that use C3 carbon fixation) like the small grains, alfalfa and soybeans. 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 Fourth of July," although modern 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 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 famine by causing maize crop failure.
Maize was planted by the Native Americans in hills, in a complex system known to some as the Three Sisters. Maize provided support for beans, and the beans provided nitrogen derived from nitrogen-fixing rhizobia bacteria which live on the roots of beans and other legumes; and squashes provided ground cover to stop weeds and inhibit evaporation by providing shade over the soil. This method was replaced by single species hill planting where each hill 60–120 cm (2.0–3.9 ft) apart was planted with three or four seeds, a method still used by home gardeners. A later technique was "checked maize", where hills were placed 40 inches apart in each direction, allowing cultivators to run through the field in two directions. In more arid lands, this was altered and seeds were planted in the bottom of 10–12 cm (3.9–4.7 in) deep furrows to collect water. Modern technique plants maize in rows which allows for cultivation while the plant is young, although the hill technique is still used in the maize fields of some Native American reservations.
In North America, fields are often planted in a two-crop rotation with a nitrogen-fixing crop, often alfalfa in cooler climates and soybeans in regions with longer summers. Sometimes a third crop, winter wheat, is added to the rotation.
Many of the maize varieties grown in the United States and Canada are hybrids. Often the varieties have been genetically modified to tolerate glyphosate or to provide protection against natural pests. Glyphosate (trade name Roundup) is an herbicide which kills all plants except those with genetic tolerance. This genetic tolerance is very rarely found in nature.
In midwestern United States, low-till or no-till farming techniques are usually used. In low-till, fields are covered once, maybe twice, with a tillage implement either ahead of crop planting or after the previous harvest. The fields are planted and fertilized. Weeds are controlled through the use of herbicides, and no cultivation tillage is done during the growing season. This technique reduces moisture evaporation from the soil and thus provides more moisture for the crop. The technologies mentioned in the previous paragraph enable low-till and no-till farming. Weeds compete with the crop for moisture and nutrients, making them undesirable.
Before World War II, most maize in North America was harvested by hand (as it still is in most of the other countries where it is grown). This involves a large numbers of workers and associated social events (husking or shucking bees). Some one- and two-row mechanical pickers were in use, but the maize combine was not adopted until after the War. By hand or mechanical picker, the entire ear is harvested, which then requires a separate operation of a maize sheller to remove the kernels from the ear. Whole ears of maize were often stored in corn cribs, and these whole ears are a sufficient form for some livestock feeding use. Few modern farms store maize in this manner. Most harvest the grain from the field and store it in bins. The combine with a maize head (with points and snap rolls instead of a reel) does not cut the stalk; it simply pulls the stalk down. The stalk continues downward and is crumpled in to a mangled pile on the ground. The ear of maize is too large to pass between slots in a plate as the snap rolls pull the stalk away, leaving only the ear and husk to enter the machinery. The combine separates out the husk and the cob, keeping only the kernels.
Worldwide maize production
Maize is widely cultivated throughout the world, and a greater weight of maize is produced each year than any other grain. The United States produces 40% of the world's harvest; other top producing countries include China, Brazil, Mexico, Indonesia,India, France and Argentina. Worldwide production was 817 million tonnes in 2009—more than rice (678 million tonnes) or wheat (682 million tonnes). In 2009, over 159 million hectares of maize were planted worldwide, with a yield of over 5 tonnes/hectare. Production can be significantly higher in certain regions of the world; 2009 forecasts for production in Iowa were 11614 kg/ha.[Note 2] 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.