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. Soils may have high levels of toxicity or salination. The crop grows as floodwaters rise, with harvesting taking place after the waters recede. Flood-prone rice is grown on more than 10 million hectares, predominately in South and Southeast Asia. The crop is heavily fertilized.