Introduction to Corn
Corn, as the term is used in the United States, a cereal plant of the grass family, producing its grain in husk-covered ears. Elsewhere in the world, this plant usually is called maize or Indian corn, while corn is a general term for all kinds of grain, particularly for the principal cereal crop of a country. In England, for example, a head of wheat is called an ear of corn.
Corn is the most important cereal crop in the United States.In the United States corn is the most important cereal crop in acreage and value. It produces the greatest yield per acre of any cereal. It not only provides food for humans but is also an important cattle feed and has many industrial uses.
The corn kernel consists of 60 to 62 per cent starch, 9 to 10 per cent protein, 3 to 4 per cent oil, and 1.2 to 1.6 per cent sugar. It is not particularly rich in any of the vitamins.
The Corn Plant
Corn is a coarse annual grass, ranging in height from 2 feet (60 cm) to more than 20 feet (6 m). The stem is pithy, not hollow as in most grasses, and is jointed like the bamboo. A long, pointed leaf springs from each joint. There may be as few as 7 leaves or as many as 45 on a single plant. The root system is fibrous. Most corn plants develop prop roots extra roots that form above ground and eventually penetrate the soil. These help to anchor the heavy plant.
The corn plant has two kinds of flowers. The male, or staminate, flowers bloom on a branching tassel at the top of the plant. They produce pollen. The female, or pistillate, flowers grow out of a spike that springs from the place where a leaf joins the stem. A single plant may have one or more spikes.
Tiny female flowers grow in rows along each spike. Each female flower consists of a few small petals and a single pistil. Each pistil consists of an ovary from which extends a long style. Together, all the styles on a spike are called the silk. The silk and spike are encased in leaves, but the tip of each style extends out beyond the leaves.
When a grain of pollen from a tassel reaches a style, the pollen germinates, forming a pollen tube that grows down the style until it reaches the single ovule in the ovary. Sperm nuclei from the pollen tube are discharged into the ovule, where one of them fertilizes the egg nucleus in the ovule. The ovary then matures into a kernel or grain and the spike develops into a pithy structure called a cob. Only those ovaries that receive pollen will produce kernels.
The kernel has three main parts. The hull is the tough outer covering. The embryo corn plant, or germ, is found in the bottom of the kernel. The rest of the kernel consists of the endosperm, a material composed largely of starch with some sugar. The endosperm serves as food for the developing germ.
The cob with its kernels is known as the ear. The ear is enclosed by long, strap-shaped leaves, called the husk. The size of the ear varies from less than six inches (15 cm) longas in some kinds of popcornto about 15 inches (38 cm) in varieties of dent corn. One extraordinary variety of Mexican corn has ears nearly three feet (90 cm) long. The grains may be white, yellow, red, brown, black, blue, or alternate colors. Most varieties of corn have yellow or white grains.
Some small varieties mature in 60 to 70 days. Larger types of corn require nearly 150 days. Giant tropical varieties take nearly 11 months to ripen.
Varieties of Corn
All cultivated corn belongs to the same species. Within this species there are six main groups, differentiated by the type of kernel:
Dent CornEach mature kernel has an indentation on the top. The dent corn plant is the largest type, reaching 8 to 15 feet (2.4-4.6 m) in height. Dent corn is the principal type grown in the United States and is widely used for feed, fodder, and silage.
Flint CornLarge, hard kernels grow on long, slender ears. The kernels on the same ear are often several different colors. Flint corn matures early and is grown mostly in northern states.
Pod CornEach kernel is covered with a husk. This is a primitive type and is little grown.
PopcornThe small, hard-hulled kernels explode when heated, turning inside out to a white, fluffy mass.
Soft Corn, or Flour CornThe soft kernels have a high starch content. Soft corn was widely grown by the Indians, but is no longer raised on a large scale in the United States.
Sweet CornThe broad, tender kernels have a high sugar content. The plant is grown in the northeastern and midwestern states. It is sold canned, frozen, or fresh.
All but pod corn and popcorn have numerous varieties. They differ in size and hardiness; in resistance to disease and insects; in the size, texture, color, and hardness of the grain; and in the nutritive value of the stalk and leaves.
Hybrid Corn
Hybrid corn is a strain produced by fertilizing one variety of corn plant with the pollen from another. The result, if the technique is carried on properly, is a strain that combines desirable features of both parents and is far superior to either. Hybrid corn produces up to 30 per cent more corn for each acre. The ears are consistently larger and better formed than those produced by ordinary methods. Stalks and roots are stronger, allowing the plant better to resist toppling by the wind. Hybrid strains have been developed to produce plants adapted to such conditions as drought, dampness, or cold.
Much painstaking work must be done to produce an ear of hybrid corn. For this reason most farmers buy hybrid seed from specialized growers.
The first step is to inbreed a desirable strain of corn for five to eight generations. Inbreeding is done by pollinating the young ear with pollen from its own plant. To prevent pollen from other plants from contacting the silk, the tassels and young ears are enclosed in bags. Inbreeding produces strains of corn that are uniformthe offspring plants have exactly the same characteristics as the parent.
The next step is to select two strains of inbred plants, each with certain desirable qualities, and to crossbreed them. This is done by placing pollen from one strain on the silk of a plant of the other strain. Usually, alternate rows of the parent inbreds are planted. The tassels are removed from the plants that are to bear the hybrid ears, so that the female-parent plants will not receive their own pollen, but will get pollen only from the male-parent plants in the adjoining rows.
This crossbreeding produces hybrid ears. Their kernels are sold to farmers as seed for hybrid plants. When two hybrid plants are crossbred, the resulting ears are called double-cross hybrids. Some of the best varieties of corn are of this type.
Kernels from the ears of double-cross hybrid plants are not used as seed. The reason is that the offsping of these plants do not resemble the parents. Each season's supply of hybrid seed must be produced by crossing the original parent strains.
Raising Corn
Corn needs a very fertile soil. The region must have adequate rainfall, but springtime must not be too wet or too cold. Corn grows best in regions where both days and nights are warm, and where rain comes in showers, followed by sunshine.
Because the corn plant takes large amounts of nutrients out of the soil, corn crops are usually rotated with other crops to prevent exhausting the soil. A common method of crop rotation is to plant corn for two years, oats the third year, and sweet clover the fourth year. The clover is plowed under to enrich the soil still further before the corn cycle begins again.
Liberal amounts of commercial fertilizer or manure are applied, either in bands on both sides of the newly planted corn, or spread over the land before plowing.
Planting and CultivatingThe soil is plowed to a depth of about six inches (15 cm) or more. The seedbed is disked and harrowed, but the soil is not broken up too finely. In the United States, mechanical planters, called wheel-track planters, are widely used; they dig the furrows, distribute the seeds in the furrows, and cover the seeds with soil. Corn is usually planted in rows 24 to 36 inches (60 to 90 cm) apart.
The soil around the growing corn must be stirred up to kill weeds. Corn fields are cultivated three or four timesuntil the plants grow too large to permit a tractor to pass among them. Chemical weed killers have been used effectively in corn fields, but they do not entirely eliminate the need for cultivation.
HarvestingThe method of harvesting depends on the type of corn. In the United States most corn grown for its grain is harvested by machine. The machines snap the ears off the stalk and deliver them to wagons. Some mechanical pickers remove the husks after picking; others do not. The picker-sheller picks the corn, removes the husks, strips the grain from the cobs, and delivers the grain into hoppers.
Corn grown for silage is harvestedstalk, leaves, ears, and alland cut into half-inch (1.3-cm) lengths. It is stored in a silo for winter cattle feed. In harvesting corn for fodder, the entire plants are taken, gathered into tepee-shaped piles called shocks, and allowed to cure in the field. Sometimes fodder corn is left standing and cattle or hogs are turned into the field. Livestock gleaning is also useful to salvage ears left behind by the picking machines.
Drying and StoringHarvested corn must be dried to prevent it from spoiling. The ears are exposed to the air in slat-wall cribs, or are dried by mechanical or electrical dryers and heaters. Stored corn is subject to attacks by insects, rats, and mice. These pests are combated by proper design of corn cribs, by fumigation, and by poisons.
Insect Pests and Diseases
More than 300 types of insects are known to damage corn. Among the most important are the European corn borer, the corn ear-worm (bollworm), the corn rootworm, the chinch bug, the fall armyworm. cutworms, wireworms, white grubs, fleabeetles, and grasshoppers. Crop rotation tends to keep some of these pests under control. Insecticides of various types are effective in many cases and certain hybrids have been developed to resist attack.
The principal diseases of corn are corn blight, smut, bacterial wilt, stalk and ear rots, and rusts. Careful control of soil quality and the use of resistant hybrids are methods of control.
Corn-producing Areas of the World
The United States leads the world in corn production, usually growing from one-third to almost half of the world's total annual crop. The great Corn Belt of the Middle West is the center of corn production. The area includes northern Kansas, eastern Nebraska, parts of southern South Dakota and Minnesota, Iowa, northern Missouri, most of Illinois and Indiana, and the western half of Ohio. Corn is grown to some extent in almost every state in the United States.
The crop in China is especially important in areas too far north for rice culture. Brazil produces and exports large quantities, and Mexico and France are also major corn producers. Other corn-growing countries include India, Romania, Argentina, Indonesia, Italy, and Canada.
Uses of Corn
How human beings use corn depends largely on their standard of living. Primitive peoples and subsistence farmers tend to use corn mainly for human food. In countries with a higher standard of living corn is used mostly for animal feed and in the manufacture of other products. Most corn products are made from ground kernels. The dry milling (grinding) process produces corn meal. The wet process is used in making starch, syrup, alcohol, and other products.
Direct UsesCorn, in the form of grain, fodder, or silage, is used as feed for cattle, hogs, and other livestock and poultry. Dent corn is usually grown for this purpose. Sweet corn is sold fresh on the cob, frozen, or canned. It is eaten primarily in North America and is almost unknown elsewhere. Flour corn is used mostly in Central and South America.
Corn is extensively used in breakfast foods, especially in a flake or puff form. Corn meal, a form of flour, is used in North America for making muffins, fritters, corn bread, mush, and many other baked foods. In Mexico and South America, corn meal is made into thin flat cakes called tortillas. Hominy is flint corn with the germ and outer hull removed. It is prepared by soaking in lye until it is white and fluffy. Grits, which are especially popular in the southern United States, are a coarsely ground form of hominy.
Indirect UsesCorn is made into many food and industrial products. One product, corn-starch, is used in baking, in thickening soups, sauces, and desserts, and as a stiffening agent in certain fabrics.
Corn syrup, another food product, is a sweetener. It is rich in fructose, an easily digested sugar. It is used in infants' formulas, candy, jelly, soft drinks, ice cream, and processed foods.
Oil obtained from the germ of the corn kernel is used in cooking, as a shortening, and in salad dressings. It is used in industry in the manufacture of soap, paints, synthetic rubber, glycerin, and many kinds of chemicals.
Bourbon and blended American whiskeys are made from corn, and their manufacture is a major industry in the United States. Other products obtained indirectly from corn include lactic acid, explosives, synthetic resins, adhesives, paper sizing, and cosmetics.
Corn stalks and husks are used to make coarse paper and wallboard. In Mexico, attractive toys are made out of corn husks. Corncobs are used as fuel and to make pipes for smoking. Industrial chemists are continually discovering new uses for corn.
History
Corn was unknown in Europe until the discovery of America. Archeologists have found evidence that a form of wild corn grew in Mexico 80,000 years ago. The origin of modern corn is uncertain; it may be a mutant of teosinte (a grass) or a hybrid involving wild corn, teosinte, and a third grass, Tripsacum.
Corn was cultivated in Mexico by 6000 B.C. The Maya, Inca, and Aztec civilizations of Central and South America used corn as a staple food. Corn was prominent in their art and in religious rites. Sculptures representing a corn god have been found among the ruins of their cities, and corn kernels have been discovered in their graves. The Aztec understood fertilization, and produced exceptionally high yields.
The Indians of North America grew corn in the southwestern part of the continent as early as 700 A.D. The use of corn spread slowly northward and eastward among the Indians, and the grain was a staple in what is now New England by 1000.
Early European explorers brought the New World grain to Spain, France, and Italy. Columbus was the first to introduce it into Europe. Later, the lives of the first European colonists in America were saved when friendly Indians brought corn to the starving settlers at Jamestown in 1607.
The Indians taught the colonists how to plant corn in small hills, using dead fish as fertilizer. The rapid growth of the American colonies was due in large part to the cultivation of corn.
Corn was distributed around the world by mariners and other travelers, and was known throughout most of the civilized world by the end of the 16th century. It seems to have been introduced into Central Europe through Turkey, and the grain is still called "Turkish wheat" in many parts of the continent.
Modern CornBreeding to produce better corn had been done to some extent since Aztec days. However, the development of the modern hybrids is comparatively recent. The first experiments were carried out in the later 19th century, and the first proposal for producing hybrids was made in 1901 by George H. Schull of the Carnegie Institution. Henry A. Wallace, later secretary of agriculture and Vice President of the United States, did much to perfect modern hybrid techniques during the 1920's.
By 1930, hybrid corn was being used on a large scale, and it now accounts for virtually all of the corn raised in the United States. The development of hybrids, together with increased use of machinery, resulted in higher corn production even though the total acreage planted in corn has been reduced. During the 1920's the average yield ranged from a little more than 20 to nearly 30 bushels per acre (1.6 to 2.4 metric tons per hectare); today the average ranges from 90 to 110 bushels per acre (7.1 to 8.6 metric tons per hectare) or more.
Using the techniques of genetic engineering, scientists produced a genetically modified type of corn in the 1990's that makes a toxin that kills certain insect pests when they feed on the plant. It was introduced for commercial planting in 1996 and, despite the public's concerns about its potentially harmful effects on the environment, acreage planted with this type of corn increased in the years following.
Cultivated corn is Zea mays of the grass family, Gramineae.