Cereal crops are mostly grasses cultivated for their edible seeds (actually a fruit called a grain, technically a caryopsis). Cereal grains are grown in greater quantities worldwide than any other type of crop and provide more food energy to the human race. In some developing nations, cereal grains constitute practically the entire diet of common folk. In developed nations, cereal consumption is more moderate but still substantial. The word cereal has its origin in the Roman goddess of grain, Ceres. Staple food grains are often called corn.
Oats, barley, and some products made from them.
The cereal crops are (in approximate order of greatest annual production):
- wheat, the primary cereal of temperate regions
- rice, the primary cereal of tropical regions
- maize, a staple food of peoples in North America, South America, and Africa and of livestock worldwide; called "corn" in North America
- the millets, a group of similar but distinct cereals that form an important staple food in Asia and Africa.
- sorghum, important staple food in Asia and Africa and popular worldwide for livestock
- rye and triticale, important in cold climates
- oats, formerly the staple food of Scotland and popular worldwide for livestock
- barley, grown for malting and livestock on land too poor for wheat
- teff, popular in Ethiopia but scarcely known elsewhere
- wild rice, grown in small amounts in the USA
- spelt, a close relative of wheat
In addition, several non-grasses are grown for their seeds. These pseudocereals include (in no particular order):
While each individual species has its own peculiarities, the cultivation of all cereals crops is similar. All are annual plants; consequently one planting yields one harvest. Wheat, rye, triticale, oats, barley, and spelt are the cool-season cereals. These are hardy plants that grow well in moderate weather and cease to grow in hot weather (approximately 30 °C but this varies by species and variety). The other warm-season cereals are tender and prefer hot weather.
Rye is the hardiest cereal, able to overwinter in the subarctic and Siberia. Wheat is the most popular. All cool-season cereals are grown in the tropics, but only in the cool highlands, where it may be possible to grow multiple crops in a year.
The warm-season cereals are grown in tropical lowlands year-round and in temperate climates during the frost-free season.
Cool-season cereals are well-adapted to temperate climates. Most varieties of a particular species are either winter or spring types. Winter varieties are sown in the autumn, germinate and grow vegetatively, then become dormant during winter. They resume growing in the springtime and mature in late spring or early summer. This cultivation system makes optimal use of water and frees the land for another crop early in the growing season. Winter varieties do not flower until springtime because they require vernalization (exposure to low temperature for a genetically determined length of time). Where winters are too warm for vernalization or exceed the hardiness of the crop (which varies by species and variety), farmers grow spring varieties. Spring cereals are planted in early springtime and mature later that same summer, without vernalization. Spring cereals typically require more irrigation and yield less than winter cereals.
Once the cereal plants have grown their seeds, they have completed their life cycle. The plants die and become brown and dry. As soon as the parent plants and their seed kernels are dry, harvest can begin.
In developed countries, cereal crops are universally machine-harvested, typically using a combine harvester, which cuts, threshes, and winnows the grain during a single pass across the field. In developing countries, a variety of harvesting methods are in use, from combines to hand tools such as scythes.
If a crop is harvested during wet weather, the grain may not dry adequately in the field to prevent spoilage during its storage. In this case, the grain is sent to a dehydrating facility, where artificial heat dries it.
In North America, farmers commonly deliver their newly harvested grain to a grain elevator, a large storage facility that consolidates the crops of many farmers. The farmer may sell the grain at the time of delivery or maintain ownership of a share of grain in the pool for later sale.
Cereal grains supply most of their food energy as starch. They are also a significant source of protein, though the amino acid balance is not optimal. Whole grains (see below) are good sources of dietary fiber, essential fatty acids, and other important nutrients.
Rice is eaten as cooked entire grains, although rice flour is also produced. Oats are rolled, ground, or cut into bits (steel_cut oats) and cooked into porridge. Most other cereals are ground into flour or meal, that is milled. The outer layers of bran and germ are removed (see grain (fruit) and seed). This lessens the nutritional value but makes the grain more appealing to many palates. Health-conscious people tend to prefer whole grains, which are not milled. Overconsumption of milled cereals is sometimes blamed for obesity. Milled grains do keep better because the outer layers of the grains are rich in rancidity-prone fats. The waste from milling is sometimes mixed into a prepared animal feed.
Once (optionally) milled and ground, the resulting flour is made into bread, pasta, desserts, dumplings, and many other products. Besides cereals, flour is sometimes made from potatoes, chestnuts and pulses (especially chickpeas).
In American English, cold breakfast cereals and porridge are called simply cereal.
See also: Zadok scale