Rice

Rice, a cereal grain, serves as the primary food for more than half the global population, especially across Africa and Asia. This grain is the seed of two grass species: the widely cultivated *Oryza sativa* (Asian rice) and the less common *Oryza glaberrima* (African rice). Asian rice was first domesticated in China between 13,500 and 8,200 years ago, while African rice was independently domesticated in West Africa roughly 3,000 years ago. By 2023, global rice production reached 800 million tons, making it the third most-produced crop after sugarcane and maize, though only about 8% of that total is traded internationally. The largest consumers are China, India, and Indonesia. In developing nations, a significant portion of harvested rice is lost after harvest due to poor transport and storage. Pests like insects, rodents, and birds, along with weeds and diseases such as rice blast, can reduce yields. Sustainable pest control methods include traditional rice-duck polycultures and modern integrated pest management.

Milling dry rice grain removes its outer layers; the extent of removal determines whether the result is brown rice, rice with germ, or white rice. Some rice is parboiled for easier cooking. Rice is gluten-free and provides protein, but lacks all essential amino acids for optimal health. The grain’s texture comes from its starch components, amylose and amylopectin. Long-grain rice, from the Indica cultivar, stays intact when cooked, turning out dry and fluffy. Aromatic varieties like basmati and jasmine, common in Asian cooking, are known for their bold, nutty flavor. Medium-grain rice—from Japonica, Indica, or a hybrid—is moist, tender, and tends to clump. Examples include Calrose, which launched California’s rice industry; Carnaroli, often called the king of Italian rice for its cooking qualities; and black rice, dark purple from anthocyanins, historically reserved for Chinese royalty as “forbidden rice.” Short-grain rice, mainly from Japonica, has an oval shape and sticky texture. It is central to Japanese dishes like sushi (using varieties such as Koshihikari, Hatsushimo, and Sasanishiki, each tied to Japan’s diverse regions), and also appears in sweet dishes like mochi (made with glutinous rice) and European dishes like risotto (with arborio rice) and paella (with bomba rice, an Indica type). Cooked white rice contains 29% carbohydrate and 2% protein, plus some manganese. Golden rice is a genetically engineered variety that produces vitamin A.

In 2022, rice production was estimated to cause over 1% of global greenhouse gas emissions. How climate change will affect rice yields varies by geography and socioeconomic conditions. Culturally, rice appears in many religious and traditional practices, including weddings.

The rice plant can grow over 1 meter tall, or up to 5 meters in deep water. From seed to harvest takes about six months. A single plant may have several leafy stems, or tillers. Its upright stem has nodes, each producing a long, slender leaf. Self-fertile flowers grow in a panicle—a branched inflorescence from the stem’s last internode—with up to 350 spikelets, each containing male and female parts (anthers and ovule). A fertilized ovule becomes the edible grain, or caryopsis. Rice belongs to the grass family Poaceae. As a tropical crop, it can grow in both dry and wet seasons if enough water is available. It is usually annual, but in the tropics it can survive as a perennial, producing a ratoon crop.

Rice growth depends on biotic factors like crop variety, pests, and diseases, and abiotic factors such as soil type (lowland or upland), water from rain or irrigation, temperature, day length, and sunlight. Grains can be sown directly in the field or grown as seedlings in a seedbed and transplanted. Direct seeding requires 60 to 80 kilograms of grain per hectare; transplanting needs less, about 40 kilograms per hectare, but demands much more labor. Most Asian rice is transplanted by hand. Mechanical transplanting is faster but needs carefully prepared fields and seedlings raised on mats or trays. Rice does not thrive if constantly submerged. Lowland fields are typically surrounded by bunds and flooded to a few centimeters until about a week before harvest, requiring large water volumes. The “alternate wetting and drying” method uses less water: fields are flooded to 5 centimeters, then allowed to drop to 15 centimeters below the surface (measured with a perforated tube), and the cycle repeats. Deepwater rice varieties tolerate flooding over 50 centimeters for at least a month. Upland rice, grown without flooding in hilly or mountainous regions, relies on rainfall like wheat or maize.

Across Asia, unmilled rice, or “paddy” (from Malay *padi*), was traditionally the product.