Rice is cultivated in tropical Asia (South and Southeast Asia) over an area of about 88.7 million ha, with an annual total production of nearly 183.8 million tons of rough rice, an average productivity of 2.7 t/ha (Table 1). Only 14% of the rice area in tropical Asia supports 2 crops of rice per year under irrigation. The remaining riceland is entirely rainfed, with varying water regimes. In areas where adequate water is available after the main crop season, rice ratooning could be practiced as an alternative to double-cropping. It is particularly suited to areas where monocropping is practiced and resources go to waste in the off-season, because no crops other than rice can be grown under the climate and moisture limitations. Such situations exist widely in hills and valleys in the tropical heavy-rainfall mountainous regions of the world.