Rice is the most important human food crop in the world, directly feeding more people than any other crop. In 2012, nearly half of world’s population – more than 3 billion people – relied on rice every day. It is also the staple food across Asia where around half of the world’s poorest people live and is becoming increasingly important in Africa and Latin America.
Rice has also fed more people over a longer time than has any other crop. It is spectacularly diverse, both in the way it is grown and how it is used by humans. Rice is unique because it can grow in wet environments that other crops cannot survive in. Such wet environments are abundant across Asia. The domestication of rice ranks as one of the most important developments in history and now thousands of rice varieties are cultivated on every continent except Antarctica.
Rice is produced in a wide range of locations and under a variety of climatic conditions, from the wettest areas in the world to the driest deserts. It is produced along Myanmar’s Arakan Coast, where the growing season records an average of more than 5,100 mm of rainfall, and at Al Hasa Oasis in Saudi Arabia, where annual rainfall is less than 100 mm. Temperatures, too, vary greatly. In the Upper Sind in Pakistan, the rice season averages 33 °C; in Otaru, Japan, the mean temperature for the growing season is 17 °C. The crop is produced at sea level on coastal plains and in delta regions throughout Asia, and to a height of 2,600 m on the slopes of Nepal’s mountains.
Rice is also grown under an extremely broad range of solar radiation, ranging from 25% of potential during the main rice season in portions of Myanmar, Thailand, and India’s Assam State to approximately 95% of potential in southern Egypt and Sudan. Rice occupies an extraordinarily high portion of the total planted area in South, Southeast, and East Asia. This area is subject to an alternating wet and dry seasonal cycle and also contains many of the world’s major rivers, each with its own vast delta. Here, enormous areas of flat, low-lying agricultural land are flooded annually during and immediately following the rainy season. Only two major food crops, rice and taro, adapt readily to production under these conditions of saturated soil and high temperatures.
Two rice species are important cereals for human nutrition: Oryza sativa, grown worldwide, and O. glaberrima, grown in parts of West Africa. These two cultigens—species known only by cultivated plants—belong to a genus that includes about 25 other species, although the taxonomy is still a matter of research and debate.
Oryza is thought to have originated about 14 million years ago in Malesia.Since then, it has evolved, diversified, and dispersed, and wild Oryza species are now distributed throughout the tropics. Their genomes can be classified into 11 groups labeled AA to LL, and most of the species can be grouped into four complexes of closely related species in two major sections of the genus (Table 1.1). Just two species, both diploids, have no close relatives and are placed in their own sections of the genus: O. australiensis and O. brachyantha.
Rice goes through a series of processes before finally reaching the table. Its production can generally be divided into the following stages: Seed selection, Land preparation, Crop establishment, Water management, Nutrient management, Crop health, Harvesting, and Postharvest.
After harvest, the rice grain undergoes a number of processes depending on how it will be used. These include, drying, storing, milling, processing, and packing – all before they are delivered to markets for sale.
Global rice production more than tripled between 1961 and 2010, with a compound growth rate of 2.24% per year (2.21% in rice-producing Asia). This increase was slightly greater than that for wheat (2.02% per year), but substantially less than that for maize, which grew at 2.71% per year. Most of the increase in rice production was due to higher yields, which increased at an annual average rate of 1.74%, compared with an annual average growth rate of 0.49% for area harvested. In absolute terms, paddy yields increased at an annual average rate of 51.1 kg/ha per year, although this rate of increase has declined in both percentage and absolute terms.
Rice is grown by more people than any other crop in the world. There are over 144 million rice farms worldwide on a harvested area of about 158 million hectares. It is cultivated in wide range of climates and terrains, by hand or using massive machinery, by small families or large agricultural corporations. The contrasts in the geographic, economic, and social conditions under which rice is produced are vast.