Chapter 2 - Rice

Abstract

This chapter emphasises the contrasting features of diverse rice agro-ecosystems as a backdrop to review crop development, growth, and resource requirement; sink–source limitation for grain yield; response to abiotic factors; and management options for grain yield and quality. For rice ecosystems defined by water regime (irrigated lowland, rainfed lowland, upland), we discuss crop establishment, water saving methods, and mechanised production. The importance of germination and crop establishment in direct-seeded rice is emphasised, followed by an outline of environmental and genetic influences on phenological development and shoot and root growth. Crop growth is further analysed in terms of capture and efficiency in the use of radiation, water, and nitrogen, with a brief description of other nutrients. Sink–source limitation in grain yield examines how the grain sink develops and how source supply is used to fill the grain. Case studies of sink–source limitation show how more recent varieties, including hybrids, have increased both sink size and assimilate supply to achieve higher yield. In response to abiotic factors, the effects of water deficit, increased CO2 concentration, submergence, high temperature, low temperature, and salinity are reviewed. The chapter identifies six topics for future research: adaptation to reduced water input in irrigated systems; adaptation to drought in rainfed lowland rice; adaptation for mechanised farming; factors determining grain set; enhancing yield potential; and enhancing head rice yield. With increased pressure on global food security because of increasing human population, scarcity of water, greater reliance on more marginal land, and climate change, the identified topics for research in rice physiology under rice-based systems must be assigned the highest priority because of vulnerability of poor subsistence farmers and consumers reliant upon rice as their staple food.