Maize (Zea mays) is a well known domesticated cereal grain first domesticated in Mexico. In much of the world it is also called corn. Worldwide cultivation of maize surpasses other prominent grains like wheat and rice. Maize must be planted in the spring due to its intolerance for cold weather.
I. Appearance and Characteristics
Maize (Zea mays), also known as corn in North American and Australian English, is a tall stout grass that produces cereal grain. It was domesticated by indigenous peoples in southern Mexico about 9,000 years ago from wild teosinte. Native Americans planted it alongside beans and squashes in the Three Sisters polyculture.
Maize is a tall annual grass with a single stem, ranging in height from 1.2 m (4 ft) to 4 m (13 ft). The long narrow leaves arise from the nodes 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 dispersed by wind. Like other pollen, it is an allergen, but most of it falls within a few meters of the tassel and the risk is largely restricted to farm workers.
The female inflorescence, some way down the stem from the tassel, is first seen as a silk, a bundle of soft 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) when it is pollinated. A whole female inflorescence develops into an ear or corn cob, enveloped by multiple leafy layers or husks. The 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.
The grains are usually yellow or white in modern varieties; other varieties have orange, red, brown, blue, 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. Yellow maizes derive their color from carotenoids; red maizes are colored by anthocyanins and phlobaphenes; and orange and green varieties may contain combinations of these pigments.
Maize has short-day photoperiodism, meaning that it requires nights of a certain length to flower. Flowering further requires enough warm days above 10 °C (50 °F). 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.
II. How to Grow and Care
Sunlight and Soil
Corn performs best in organically rich, acidic to neutral (pH ranging from 5.5 to 7.0), moist, but well-drained soils in full sun (at least 6-8 hours of direct sunlight per day) in a sheltered location.
Temperature
Corn is a warm-weather crop that is sensitive to frost and should not be planted until the soil warms up to 60°F (15°C) or 75°F (24°C) for supersweet varieties. Seed planted in cooler soil is prone to many problems, including poor germination.
Planting Instructions
- Before planting, add well-rotted organic matter or compost and work it into the soil.
- Keep the soil evenly moist but not soggy. Corn has shallow roots and can become stressed by drought. Water the ground, not the plant, or pollination could suffer.
- Sow seeds 1½ to 2 in. deep (3-5 cm) and 2-4 in. apart (5-10 cm). Water thoroughly at planting time.
- After planting, use a row cover for about a month to boost the seedlings.
- When seedlings are close to 4 in. tall (10 cm), thin them to 12-18 in. apart (30-45 cm) for short varieties and 18-24 in. apart (45-60 cm) for tall varieties.
- Corn is a heavy feeder and must have ample nitrogen. Side-dress plants with a high-nitrogen fertilizer when Corn is 8 in. tall (20 cm) and again when it is 18 in. tall (45 cm).
- Rotate crops: Do not plant Corn where it has grown in the past 2 years to prevent issues.
Pollination
Corn is pollinated by the wind. Each Corn silk is attached to a kernel of Corn, and each must be pollinated for that kernel to grow. As a result, it is best to plant Corn in blocks (all the same variety) rather than long single rows to ensure good pollination. A minimum of 15 or more plants is usually necessary. To help pollination, you may want to gently shake the stalks of the plants every few days (in the morning) until the tassels are no longer viable.
Pests and Diseases
Many pests can affect maize growth and development, including invertebrates, weeds, and pathogens.
Maize is susceptible to a large number of fungal, bacterial, and viral plant diseases. Those of economic importance include diseases of the leaf, smuts such as corn smut, ear rots and stalk rots. Northern corn leaf blight damages maize throughout its range, whereas banded leaf and sheath blight is a problem in Asia. Some fungal diseases of maize produce potentially dangerous mycotoxins such as aflatoxin. In the United States, major diseases include tar spot, bacterial leaf streak, gray leaf spot, northern corn leaf blight, and Goss’s wilt; in 2022, the most damaging disease was tar spot, which caused losses of 116.8 million bushels.
Maize sustains a billion dollars’ worth of losses annually in the US from each of two major insect pests, namely the European corn borer or ECB (Ostrinia nubilalis) and corn rootworms (Diabrotica spp) western corn rootworm, northern corn rootworm, and southern corn rootworm. Another serious pest is the fall armyworm (Spodoptera frugiperda). The maize weevil (Sitophilus zeamais) is a serious pest of stored grain. The Northern armyworm, Oriental armyworm or Rice ear-cutting caterpillar (Mythimna separata) is a major pest of maize in Asia.
Nematodes too are pests of maize. It is likely that every maize plant harbors some nematode parasites, and populations of Pratylenchus lesion nematodes in the roots can be “enormous”. The effects on the plants include stunting, sometimes of whole fields, sometimes in patches, especially when there is also water stress and poor control of weeds.
Many plants, both monocots (grasses) such as Echinochloa crus-galli (barnyard grass) and dicots (forbes) such as Chenopodium and Amaranthus may compete with maize and reduce crop yields. Control may involve mechanical weed removal, flame weeding, or herbicides.
III. Uses and Benefits
Culinary uses
Maize and cornmeal (ground dried maize) constitute a staple food in many regions of the world. Maize is used to produce the food ingredient cornstarch. Maize starch can be hydrolyzed and enzymatically treated to produce high fructose corn syrup, a sweetener. Maize may be fermented and distilled to produce Bourbon whiskey. Corn oil is extracted from the germ of the grain.
In prehistoric times, Mesoamerican women used a metate quern to grind maize into cornmeal. After ceramic vessels were invented the Olmec people began to cook maize together with beans, improving the nutritional value of the staple meal. Although maize naturally contains niacin, an important nutrient, it is not bioavailable without the process of nixtamalization. The Maya used nixtamal meal to make porridges and tamales. Maize is a staple of Mexican cuisine. Masa (nixtamal) is the main ingredient for tortillas, atole and many other dishes of Central American food. It is the main ingredient of corn tortilla, tamales, atole and the dishes based on these. The corn smut fungus, known as huitlacoche, which grows on maize, is a Mexican delicacy.
Coarse maize meal is made into a thick porridge in many cultures: from the polenta of Italy, the angu of Brazil, the mămăligă of Romania, to cornmeal mush in the US (or hominy grits in the Southern US) or the food called mieliepap in South Africa and sadza, nshima, ugali and other names in other parts of Africa. Introduced into Africa by the Portuguese in the 16th century, maize has become Africa’s most important staple food crop.
Sweet corn, a genetic variety that is high in sugars and low in starch, is eaten in the unripe state as corn on the cob.
Other uses
- Nutritional value
Raw, yellow, sweet maize kernels are composed of 76% water, 19% carbohydrates, 3% protein, and 1% fat (table). In a 100-gram serving, maize kernels provide 86 calories and are a good source (10–19% of the Daily Value) of the B vitamins, thiamin, niacin (if freed), pantothenic acid (B5) and folate. Maize has suboptimal amounts of the essential amino acids tryptophan and lysine, which accounts for its lower status as a protein source. The proteins of beans and legumes complement those of maize.
- Animal feed
Maize is a major source of animal feed. As a grain crop, the dried kernels are used as feed. They are often kept on the cob for storage in a corn crib, or they may be shelled off for storage in a grain bin. When the grain is used for feed, the rest of the plant (the corn stover) can be used later as fodder, bedding (litter), or soil conditioner. When the whole maize plant (grain plus stalks and leaves) is used for fodder, it is usually chopped and made into silage, as this is more digestible and more palatable to ruminants than the dried form.
Traditionally, maize was gathered into shocks after harvesting, where it dried further. It could then be stored for months until fed to livestock. Silage can be made in silos or in silage wrappers. In the tropics, maize is harvested year-round and fed as green forage to the animals. Baled corn stalks offer an alternative to hay for animal feed, alongside direct grazing of maize grown for this purpose.
- Chemicals
Starch from maize can be made into plastics, fabrics, adhesives, and many other chemical products. Corn steep liquor, a plentiful watery byproduct of maize wet milling process, is used in the biochemical industry and research as a culture medium to grow microorganisms.
- Biofuel
Feed maize is being used for heating; specialized corn stoves (similar to wood stoves) use either feed maize or wood pellets to generate heat. Maize cobs can be used as a biomass fuel source. Home-heating furnaces which use maize kernels as a fuel have a large hopper that feeds the kernels into the fire. Maize is used as a feedstock for the production of ethanol fuel. The price of food is indirectly affected by the use of maize for biofuel production: use of maize for biofuel production increases the demand, and therefore the price of maize. A pioneering biomass gasification power plant in Strem, Burgenland, Austria, started operating in 2005. It would be possible to create diesel from the biogas by the Fischer Tropsch method.
IV. Harvesting and Storage
Harvest your Corn when the ears reach maturity, the corn silk turns brown, and the cob becomes more rounded towards the bottom. Kernels that are ready for eating have a milky white interior. Try shucking a small section of the corn ear and piercing a kernel to check.
If you want to dry your Corn for seed or storage, leave the cobs of Corn on the stalk for 6 to 8 more weeks.
After harvest, cut or mow stalks and let them dry. Then turn them under or collect and compost them. Destroy any diseased or infested material.
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