The rest is mostly water, with minute amounts of phosphorus, potassium, calcium and B vitamins. Brown rice is produced by leaving some of the external layers of bran on the kernel in the milling process. The O. sativa rice species has been grown for more than 4,000 years. The cooking quality of rice is determined by the percentage of the starch component, known as amylose. Rice ecosystems are characterized by elevation, rainfall patterns, depth of flooding and drainage.
Yields tend to be low due to a lack of moisture and inadequate nutrition.
Upland rice is grown on more than 19 million hectares worldwide, largely in Latin America and Africa. Rainfed lowland - Rice is transplanted or direct seeded in puddled soil on level, slightly sloping or diked fields. The depth and duration of flooding is dependent on local rainfall. Yields depend on rainfall, cultivation practices and use of fertilizer. Rainfed lowland rice is grown on 37 million hectares worldwide, and is dominant in humid and subhumid tropics.