Chapter 6 Strategies for Producing More Rice with Less Water

Rice is life for more than half of humanity. It is the grain that has shaped the cultures, diets, and economies of billions of people in the world. Food security in the world is challenged by increasing food demand and threatened by declining water availability. More recently, the increase in area under biofuel crops at the cost of food crops is also threatening. Exploring ways to produce more rice with less water is essential for food security. Water-saving rice production systems, such as aerobic rice culture, system of rice intensification (SRI), ground-cover rice production system (GCRPS), raised beds, and alternate wetting and drying (AWD), can drastically cut down the unproductive water outflows and increase water-use efficiency (WUE). However, these technologies can sometimes lead to some yield penalty, if the existing lowland varieties are used. Other new approaches are being explored to increase water economy without compromise on yield. These include the incorporation of the C₄ photosynthetic pathway into rice to increase rice yield per unit water transpired, the use of molecular biotechnology to develop rice varieties with improved water-use efficiency, transpiration efficiency (TE), drought tolerance, and the development of varieties for aerobic system, to achieve high and sustainable yields in nonflooded soil. Through the adoption of water-saving irrigation technologies, rice land will shift away from being continuously anaerobic to being partly or even completely aerobic. These shifts will produce profound changes in water conservation, soil organic matter turnover, nutrient dynamics, carbon impounding, weed flora, and greenhouse gas emissions. Although some of these changes can be positive, for example, water conservation and decreased methane emission, others might be negative, for example, release of nitrous oxide from the soil and decline in soil organic matter. The challenge will be to develop effective integrated natural-resource-management interventions, which would allow profitable rice cultivation with increased soil aeration, while maintaining the productivity, environmental safety, and sustainability of rice-based ecosystems. This chapter discusses the integrated approaches like genetics, breeding, and resource management to increase rice yield and to reduce water demand for rice production.