Examining the water-shortage problem in rice systems: water-saving irrigation technologies
2003
Bouman, B.A.M.
Rice production in Asia needs to increase to feed an ever-growing population. More than 75% of the rice produced comes from irrigated land. However, the water crisis threatens the sustainability of the irrigated system. The supply of water for irrigation is endangered by declining water quality, declining resource availability, increased competition from other users, and increasing costs. Rice is especially sensitive to declining water availability since it requires more water than any other food crop and it has a relatively low water-use efficiency. At the farm level, water inputs can be reduced by decreasing the relatively large and unproductive losses from seepage, percolation, and evaporation. Water-saving irrigation technologies such as saturated soil culture and alternate wetting and drying can drastically diminish these losses. Under these technologies, yields also decline, though to a lesser extent than the water inputs, hence, water productivities increase. A new concept of growing rice using less water is aerobic rice: high-yielding rice grown in nonpuddled aerobic soil using supplementary irrigation just like upland crops. Farmers in Brazil, China, and India are pioneering this system where water is scarce or costly. However, new aerobic rice varieties and specially designed management strategies are needed if this system is going to be successful. Through the adoption of water-saving irrigation technologies, rice land will shift away from being continuously anaerobic to being partly or even completely aerobic. This will have major consequences for other aspects of sustainability, such as weed, pest, and disease ecology and nutrient and soil organic matter dynamics.
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