All cereal crops are cultivated in a similar way. Most are
annual, so after sowing they are harvested just once. Cereals adapted to a
temperate climate, such as
barley,
oats,
rye,
spelt,
triticale, and
wheat, are called cool-season cereals. Those preferring a
tropical climate, such as
millet and
sorghum, are called warm-season cereals. Cool-season cereals, especially rye, followed by barley, are hardy; they grow best in fairly cool weather, and stop growing, depending on variety, when the temperature goes above around . Warm-season cereals, in contrast, require hot weather and cannot tolerate frost. Cool-season cereals can be grown in highlands in the tropics, where they sometimes deliver several crops in a single year. though some strains are grown on dry land. Other warm climate cereals, such as sorghum, are adapted to arid conditions. Cool-season cereals are grown mainly in temperate zones. These cereals often have both winter varieties for autumn sowing, winter dormancy, and early summer harvesting, and spring varieties planted in spring and harvested in late summer. Winter varieties have the advantage of using water when it is plentiful, and permitting a second crop after the early harvest. They flower only in spring as they require
vernalization, exposure to cold for a specific period, fixed genetically. Spring crops grow when it is warmer but less rainy, so they may need irrigation. Fusarium head blight, caused by
Fusarium graminearum, is a significant limitation on a wide variety of cereals. Other pressures include
pest insects and wildlife like rodents and deer. In conventional agriculture, some farmers apply
fungicides or pesticides.
Harvesting Annual cereals die when they have come to seed, and dry up. Harvesting begins once the plants and seeds are dry enough. Harvesting in mechanized agricultural systems is by
combine harvester, a machine which drives across the field in a single pass in which it cuts the stalks and then
threshes and
winnows the grain. In traditional agricultural systems, mostly in the
Global South, harvesting may be by hand, using tools such as
scythes and
grain cradles. It is used in crafts such as building with
cob or
straw-bale construction. File:Rice-combine-harvester, Katori-city, Japan.jpg|A small-scale rice
combine harvester in Japan
Preprocessing and storage If cereals are not completely dry when harvested, such as when the weather is rainy, the stored grain will be spoilt by
mould fungi such as
Aspergillus and
Penicillium. This can be prevented by drying it artificially. It may then be stored in a
grain elevator or
silo, to be sold later. Grain stores need to be constructed to protect the grain from damage by pests such as seed-eating birds and
rodents. In developing countries, processing may be traditional, in artisanal workshops, as with
tortilla production in Central America. Most cereals can be processed in a variety of ways.
Rice processing, for instance, can create whole-grain or polished rice, or rice flour. Removal of the germ increases the longevity of grain in storage. Some grains can be
malted, a process of activating enzymes in the seed to cause sprouting that turns the complex starches into sugars before drying. These sugars can be extracted for industrial uses and further processing, such as for making
industrial alcohol, or
rice wine, In the 20th century,
industrial processes developed around chemically altering the grain, to be used for other processes. In particular,
maize can be altered to produce food additives, such as
corn starch and
high-fructose corn syrup. == Effects on the environment ==