Rice

Rice can be direct-sown into wet or dry seedbeds or raised as seedlings and transplanted into flooded paddies; seedlings typically emerge within one to two weeks, and the crop needs warm temperatures of roughly 50°F to 100°F, planted after the last frost in a site getting six to eight hours of direct sun daily. Commercial fields are leveled to allow uniform flooding and drainage and rely on a hard subsoil layer that limits water seepage; seed may be sown by air into already-flooded fields or drilled or broadcast into dry fields before flooding.

Lowland rice is grown standing in flooded paddies kept topped up with non-chlorinated water, while upland rice is grown without standing water but still needs regular watering, at least an inch weekly, with soil kept consistently moist but not waterlogged. Fertile, water-retentive soils such as heavy clay or loam are favored, and monthly applications of an organic fertilizer such as fish emulsion support growth.

Rice yields can be reduced by insect, rodent, and bird pests, by weeds, and by diseases such as rice blast. Traditional polycultures such as rice-duck farming, alongside modern integrated pest management, are used to control this damage sustainably.

After the heading phase, when wind-pollinated flowers form along the stems, grains mature over about 30 days before harvest. In some warm regions, fields are reflooded after the main harvest so that a partial second, or "ratoon," crop can grow from the remaining stubble.

Once harvested, a substantial amount of the rice grown in developing nations is subsequently lost to poor transport and storage.

Rice is the staple food for more than half the world's population, particularly in Asia and Sub-Saharan Africa, providing carbohydrate and protein though it contains no gluten. The harvested grain is milled to varying degrees to produce white rice or left intact as brown rice with its bran and germ, and it is further processed into products such as rice flour, rice syrup, rice bran oil, and rice milk.

Asian rice was domesticated in China roughly 13,500 to 8,200 years ago from a wild grass ancestor in the Graminaceae family. Cultivation later spread from East Asia to the Indian subcontinent, where local wild rice hybridized with japonica rice that had arrived from its East Asian center of origin, giving rise between about 4,000 and 2,400 years ago to the aromatic group of rice; aus is regarded as the original crop of the Indian subcontinent, with indica and japonica arriving there later.