ABSTRACT
Asia’s food security depends largely on the irrigated rice fields, which produces three quarters of all rice harvested. But rice is a profligate user of water, consuming half of all developed fresh water resources. The increasing scarcity of water threatens the sustainability of the irrigated rice production system and hence the food security and livelihood of rice producers and consumers. In Asia, 17 million ha of irrigated rice areas may experience “physical water scarcity’’ and 22 million ha may have “economic water scarcity’’ by 2025 (Tuong and Bouman, 2001). Therefore, a more efficient use of water is needed in rice production. Several strategies are being pursued to reduce rice water requirements, such as saturated soil culture (Borrel et al., 1997), alternate wetting and drying (Li 2001, Tabbal et al., 2002), ground cover systems (Lin Shan et al., 2002), system of rice intensification (SRI, Stoop et al., 2002), aerobic rice (Bouman et al., 2002), and raised beds (Singh et al., 2002). It is reported that SRI and AWD systems have high water productivity with some amount of saving (approx. 20 per cent) without any compromise on productivity. However, water requirement of these production systems is also very high as land preparation consists of soaking, followed by wet ploughing or puddling of saturated soil. Further, when standing water is kept in the field (5-10 cm) during crop growth, large amount of water (about 10-15 per cent) is lost through seepage and percolation. Every drop of water received at the farmer’s field by way of rainfall, surface irrigation or pumped from aquifers, is valuable and needs to be used effectively. Aerobic rice provides for effective use of rain that falls on the farmer’s field, as there is no standing water and the farmer can skip irrigation if soil moisture status is sufficient for crop. This is not possible if water is already standing in the filed.
