Rice



Rice (genus Oryza) is a plant of the grass family which feeds more than half of the world's human population. Rice cultivation is well suited to countries with low labor costs, but high rainfall as it is very labor-intensive to cultivate and requires plenty of water for irrigation. However it can be grown practically anywhere, even on steep hillsides. Rice is the world's third largest crop, behind maize(corn) and wheat.

Rice cultivation

Rice is often grown in paddies ? shallow puddles (typically 15 cm depth) carefully controlled to ensure the appropriate water depth. Rice paddies sometimes serve a dual agricultural purpose by also producing edible fish or frogs, a useful source of protein. The farmers take advantage of the rice plant's tolerance to water: the water in the paddies prevents weeds from outgrowing the crop. Once the rice has established dominance of the field, the water can be drained in preparation for harvest. Paddies increase productivity, although rice can also be grown on dry land (including on terraced hillsides) with the help of chemical weed controls.

In some instances, a deepwater strain of rice often called floating rice is grown. This can develop elongated stems capable of coping with water depths exceeding 2 meters (6 feet).

Rice paddies are an important habitat for birds such as herons and warblers, and a wide range of amphibians and snakes. They perform a useful function in controlling insect pests.

Whether it is grown in paddies or on dry land, rice requires a great amount of water compared to other food crops. Rice growing is a controversial practice in some areas, particularly in the United States and Australia, where rice farmers use 7% of the nation's water to generate just 0.02% of GDP. However, in nations that have a periodical rain season and typhoons, rice paddies serve to keep the water supply steady and prevent floods from reaching a dangerous level.

Preparation as food

The seeds of the rice plant are first milled to remove the outer husks of the grain; this creates brown rice. This process may be continued, removing all of the husk, creating 'white' rice. The white rice may then be buffed with glucose or talc powder, parboiled, or processed into flour. Most inner oily layer called nuka is heated to remove its oil and then used for making pickled vegetables.

The processed rice seeds are usually boiled or steamed to make them edible, after which they may be fried in oil or butter.

Two rice varieties were domesticated Asian rice O. sativa and African rice O. glaberrima. It is commonly agreed that common wild rice (Oryza rufipogon Griff.) was the wild ancestor of the Asian cultivated rice. O. sativa [1] (http://station7.kgw.tu-berlin.de/english/abstracts/ChenW.html).

Oryza sativa was domesticated in ancient China [2] (http://www.carleton.ca/~bgordon/Rice/paper_database.htm) circa 6000 BC to 5000 BC, although some make claims for older finds. None of those claims for earlier rice remains have yet been directly dated. The genetic origin of the landraces of O. sativa indica and japonica, remains uncertain.

African rice Otyza glaberrima has been cultivated in Africa for 3500 years, and is well adapted to the African environment. However it has lower yields than Asian rice.

Dry-land rice was introduced to Japan circa 1000 BC. Later wet-paddy rice agriculture was brought to Japan by the Yayoi circa 300 BC. From India rice spread to southern Europe, O. sativa crop was common in West Africa by the end of the 17th century, grown for increased yields over the local variety.

Colonial South Carolina and Georgia grew and amassed great wealth from the slave labor obtained from the Senegambia area of West Africa. At the Port of Charleston, through which 40% of all American slave imports passed, slaves from this region of Africa brought the highest prices, in recognition of their prior knowledge of rice culture, which was put to use on the many rice plantations around Georgetown, Charleston, and Savannah. From the slaves, plantation owners learned how to dike the marshes and periodically flood the fields. At first the rice was milled by hand with wooden paddles, then winnowed in sweetgrass baskets (the making of which was another skill brought by the slaves). The invention of the rice mill increased profitability of the crop, and the addition of water power for the mills in 1787 by millwright Jonathan Lucas was another step forward. Rice culture in southeastern USA became less profitable with the loss of slave labor after the American Civil War, and it finally died out just after the turn of the 20th century.

The United States is a major rice producing and exporting country. It supplies approximately 12% of the global rice market. Arkansas, Louisiana, California, Mississippi, Texas, and Missouri are the largest producing states. Arkansas is the leading producer with just under half of the total United States rice production in 2003.

Rice varieties are often classified by their grain shapes. For example, Thai or Siamese Jasmine rice is long-grain and relatively less sticky, as long-grain rice contains less starch than short-grain varieties. Chinese restaurants usually serve long-grain as plain unseasoned steamed rice. Japanese rice and Chinese sticky rice are short-grain. Chinese people use sticky rice which is properly known as "glutinous rice" (despite the fact that no form of rice actually contains gluten) to make dumplings.

Indian rice varieties include long-grained Basmati (grown in the North), medium-grained Patna and short-grained Masoori. One variety used widely in South India, is usually referred to in English as boiled rice or parboiled rice. This is prepared by boiling the rice in large pans immediately after harvesting, often over coconut-shell fires, to kill any fungi or other contaminants. It is then dried, and the husk removed later. It often displays small red speckles, and has a smoky flavour from the fires. This rice is used mainly to make idlis.

Aromatic rices have definite aromas and flavors; the most noted varieties are the aforementioned basmati, and a hybrid of basmati and American long-grain rice sold under the trade name, Texmati, both of which have a mild popcorn-like aroma and flavor.

High-yield varieties of rice suitable for cultivation in Africa and other dry ecosystems called the new rice for Africa (NERICA) cultivars have been developed. Their cultivation will hopefully improve food security in West Africa.

Scientists are working on so-called golden rice which is genetically modified to produce beta carotene, the precursor to vitamin A. This has generated a great deal of controversy over whether the amount of beta carotene would be significant and whether genetically modified foods are desirable.

Draft genomes for the two commonest rice cultivars, indica and japonica, were published in April 2002. Rice was chosen as a model organism for the biology of grasses beacuse of its relatively small genome (~430 Megabases).