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Wheat (Triticum spp.) is a grass that is cultivated worldwide. Globally, it is the most important human food grain and ranks second in total production as a cereal crop behind maize; the third being rice. Wheat grain is a staple food used to make flour for leavened, flat and steamed breads; cookies, cakes, pasta, noodles and couscous; and for fermentation to make beer, alcohol, vodka or biofuel. The husk of the grain, separated when milling white flour, is bran. Wheat is planted to a limited extent as a forage crop for livestock and the straw can be used as fodder for livestock or as a construction material for roofing thatch.
History The first cereal known to have been domesticated, wheat originated in southwest Asia in the area known as the Fertile Crescent. The earliest archaeological evidence for wheat cultivation comes from the Levant and Turkey. Around 10,000 years ago, Agricultural cultivation using horse collar leveraged plows (3000 years B.P.) increased cereal grain productivity yields, as did the use of seed drills which replaced broadcasting sowing of seed in the 18th century. Yields of wheat continued to increase, as new land came under cultivation and with improved agricultural husbandry involving the use of fertilizers, threshing machines and reaping machines (the 'combine harvester'), tractor-draw cultivators and planters, and better varieties (see green revolution and Norin 10 wheat). With population growth rates falling, while yields continue to rise, the acreage devoted to wheat may now begin to decline for the first time in modern human history. Genetics and breeding Wheat genetics is more complicated than that of most other domesticated species. Some wheat species occur as stable polyploids, having more than two sets of diploid chromosomes.Hancock, James F. (2004) Plant Evolution and the Origin of Crop Species. CABI Publishing. ISBN 0-85199-685-X. Heterosis or hybrid vigor (as in the familiar F1 hybrids of maize) occurs in common (hexaploid) wheat, but it is difficult to produce seed of hybrid cultivars on a commercial scale as is done with maize because wheat flowers are complete and normally self-pollinate.Bajaj, Y. P. S. (1990) Wheat. Springer. pp. 161-63. ISBN 3-540-51809-6. Commercial hybrid wheat seed has been produced using chemical hybridizing agents, plant growth regulators that selectively interfere with pollen development, or naturally occurring cytoplasmic male sterility systems. Hybrid wheat has been a limited commercially success, in Europe (particularly France), the USA and South Africa.Basra, Amarjit S. (1999) Heterosis and Hybrid Seed Production in Agronomic Crops. Haworth Press. pp. 81-82. ISBN 1-56022-876-8. F1 hybrid wheat cultivars should not be confused with standard method of breeding inbred wheat cultivars by crossing two lines using hand emasculation, then selfing or inbreeding the progeny many (ten or more) generations before release selections are identified to released as a variety or cultivar. Hulled versus free-threshing wheat Four wild species of wheat, and in the domesticated einkorn Naming There are many taxonomic classification systems used for wheat species, discussed in a separate article on Wheat taxonomy. It is good to keep in mind that the name of a wheat species from one information source may not be the name of a wheat species in another. Within a species, wheat cultivars are further classified by growing season, such as winter wheat vs. spring wheat, by gluten content, such as hard wheat (high protein content) vs. soft wheat (high starch content), or by grain color (red, white or amber). Major cultivated species of wheat Economics
Costs and Returns In Western Europe target wheat yields attainable are around 8 tonnes / hectare. Until recently a tonne of wheat was worth around 90 euros / tonne, giving a total income of 630 euros per hectare for an average yield of 7 tonnes / hectare. European Union subsidies available in 2006 add 400 euros / hectare, giving a total income of 1,030 euros. In some instances the straw yield of around 4 tonnes per hectare may be saleable at between 9 and 30 euros / tonne. Seed, fertiliser and pesticides cost around 60 euros, 100 and 160 euros respectively. Labour cost comes to about 200 euros, Power and Machinery 200, while rent and overheads come to around 250 euros per hectare for a large scale arable farm of over 200 hectares. Smaller farms would have higher costs due to economy of scale differences. With total costs of 970 euros a small profit of 60 euros per hectare, or 12,000 euros per year income for 200 hectares is available to the farmer for living expenses and loan repayments. The recent world price rises (2006) for wheat as a commodity could bring in as much as 400 euros per hectare extra for producers. Organic wheat typically halves yield attainable but costs less as there are no fertiliser and pesticide costs. Seed costs are typically higher, however, and arguably labour and machinery costs are higher as the organic crop, and more importantly the whole rotation and cropping on such a farm, is more difficult to manage correctly. Production and consumption statistics
Crop development While winter wheat lies dormant during a winter freeze, wheat normally requires between 110 and 130 days between planting and harvest, depending upon climate, seed type, and soil conditions. 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 Zadoks scale). Knowledge of stages is also interesting to identify periods of higher risk, in terms of climate. For example, the meïosis stage is extremely susceptible 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 ensure 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. Wheat stages
Diseases Estimates of the amount of wheat production lost owing to plant diseases vary between 10-25% in Missouri*. A wide range of organisms infect wheat, of which the most important are viruses and fungi. Main article: Wheat diseases Pests Wheat is used as a food plant by the larvae of some Lepidoptera species including The Flame, Rustic Shoulder-knot, Setaceous Hebrew Character and Turnip Moth. Wheat in the United States 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. Wheat as a symbol Wheat is also used as a symbol, mostly the symbol of the working class. Image:Soviet coat of arms.png|symbol Soviet coat of arms See also | |||||||||||||||||||||||||||||||||||||||||
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