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Wheat
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Wheat cultivars are classified by growing season (winter wheat vs. spring wheat) and by gluten content (hard wheat (high gluten content) vs. soft wheat (high starch content)).
Wheat originated in ancient Mesopotamia. The oldest archaeological evidence for wheat cultivation comes from Syria, Jordan, Turkey, and Iraq. Around 8,000 years ago, a mutation or hybridization occurred within emmer, resulting in a plant with seeds that were larger, but could not sow themselves on the wind. While this plant could not have succeeded in the wild, it produced more food for humans, and within cultivated fields, it outcompeted plants with smaller, self-sowing seeds to become the ancestor of modern wheat.
In the 2002 crop year, global wheat production totalled 563.2 million tonnes and the top wheat producing countries were:
1997 global per capita wheat consumption was 101 kg, led by Denmark at 623 kg.
Past International wheat production statistics.
Crop management decisions require the knowledge of stage of development of the crop. In particular, spring fertilizers applications, herbicides, fungicides, growth regulators are typically applied at specific stages of plant development.
For example, current recommendations often indicate the second application of nitrogen be done when the ear (not visible at this stage) is about 1 cm in size (Z31 on Zadok scale). Knowledge of stages is also interesting to identify periods of higher risk, in terms of climate. For example, the meïosis stage is extremely suceptible to low temperatures (under 4°C) or high temperatures (over 25°C). Farmers also benefit from knowing when the flag leaf (last leaf) appears as this leaf represents about 75% of photosynthesis reactions during the grain filling period and as such should be preserved from disease or insect attacks to insure a good yield.
Several systems exist to identify crop stages, with the Feekes and Zadoks scales being the most widely used. Each scale is a standard system which describes successive stages reached by the crop during the agricultural season.
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Wheat is subject to more diseases than other grains, and, in some seasons, especially in wet ones, heavier losses are sustained from those diseases than are felt in the culture of any other culmiferous crop with which we are acquainted. Wheat may suffer from the attack of insects at the root; from blight, which primarily affects the leaf or straw, and ultimately deprives the grain of sufficient nourishment; from mildew on the ear, which operates thereon with the force of an apoplectic stroke; and from gum of different shades, which lodges on the chaff or cups in which the grain is deposited.
Examples of wheat diseases:
Bacterial diseases
Fungal diseases
Nematodes, parasitic
Viral diseases and viruslike agents
Phytoplasmal diseases
Harvested wheat grain is classified according to grain properties (see below) for the purposes of the commodities market. Wheat buyers use the classifications to help determine which wheat to purchase as each class has special uses. Wheat producers determine which classes of wheat are the most profitable to cultivate with this system.
Wheat is widely cultivated as a cash crop because it produces a good yield per unit area, grows well in a temperate climate even with a moderately short growing season, and yields a versatile, high-quality flour that is widely used in baking. Most breads are made with wheat flour, even many breads named for the other grains they contain, including most rye and oat breads. Many other popular foods are made from wheat flour as well, resulting in a large demand for the grain even in economies with a significant food surplus.
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Classes used in the United States are
Hard wheats are harder to process and red wheats may need bleaching. Therefore, soft and white wheats usually command higher prices than hard and red wheats on the commodities market.
Much of the following text is taken from the Household Cyclopedia of 1881:
Wheat may be classed under two principal divisions, though each of these admits of several subdivisions. The first is composed of all the varieties of red wheat. The second division comprehends the whole varieties of white wheat, which again may be arranged under two distinct heads, namely, thick-chaffed and thin-chaffed.
Thick-chaffed wheat varieties were the most widely used before 1799, as they generally make the best quality flour, and in dry seasons, equal the yields of thin-chaffed varieties. However, thick-chaffed varieties are particularly susceptible to mildew, while thin-chaffed varieties are quite hardy and in general are more resistant to mildew. Consequently, a widespread outbreak of mildew in 1799 began a gradual decline in the popularity of thick-chaffed varieties.
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