Introduction :-
Rice is a cereal grain and in its domesticated form is the staple food of over half of the world’s population, particularly in Asia and Africa. Rice is the seed of the grass species Oryza sativa (Asian)—or, much less commonly, Oryza glaberrima (African). Asian rice was domesticated in China some 13,500 to 8,200 years ago; African rice was domesticated in Africa about 3,000 years ago. It has become commonplace in many cultures worldwide; in 2021, 787 million tons were produced, placing it fourth after sugarcane, maize, and wheat.
Only some 8% of rice is traded internationally. China, India, and Indonesia are the largest consumers of it. A substantial amount of the rice produced in developing nations is lost after harvest through factors such as poor transport and storage. Its yields can be reduced by pests including insects, rodents, and birds, as well as by weeds, and by diseases such as rice blast. Traditional rice polycultures such as rice-duck farming, and modern integrated pest management seek to control damage from pests in a sustainable way.
Many varieties of rice have been bred to improve crop quality and productivity. Biotechnology has created Green Revolution rice able to produce high yields when supplied with nitrogen fertiliser and managed intensively. Other products are able to express human proteins for medicinal use; flood-tolerant or deep water rice; and drought-tolerant and salt-tolerant varieties. It is used as a model organism in biology.
Description :-
Its plant can grow to over 1 m (3 ft) tall; if in deep water, it can reach a length of 5 m (16 ft). A single plant may have several leafy stems or tillers. The upright stem is jointed with nodes along its length; a long slender leaf arises from each node. The self-fertile flowers are produced in a panicle, a branched inflorescence which arises from the last internode on the stem. There can be up to 350 spikelets’ in a panicle, each containing male and female flower parts (anthers and ovule). A fertilised ovule develops into the edible grain or caryopsis.
It is a cereal belonging to the family Poaceae. As a tropical crop, it can be grown during the two distinct seasons (dry and wet) of the year provided that sufficient water is made available. It is normally an annual, but in the tropics it can survive as a perennial, producing a ratoon crop.
Agronomy :-
- Growing:
Like all crops, rice depends for its growth on both biotic and abiotic environmental factors. The principal biotic factors are crop variety, pests, and plant diseases. Abiotic factors include the soil type, whether lowland or upland, amount of rain or irrigation water, temperature, day length, and intensity of sunlight.
Its grains can be planted directly into the field where they will grow, or seedlings can be grown in a seedbed and transplanted into the field. Direct seeding needs some 60 to 80 kg of grain per hectare, while transplanting needs less, around 40 kg per hectare, but requires far more labour. Mostly rice in Asia is transplanted by hand. Mechanical transplanting takes less time but requires a carefully-prepared field and seedlings raised on mats or in trays to fit the machine. It does not thrive if continuously submerged.
It can be grown in different environments, depending upon water availability. The usual arrangement is for lowland fields to be surrounded by bunds and flooded to a depth of a few centimetres until around a week before harvest time; this requires a large amount of water. The “alternate wetting and drying” technique uses less water.
One form of this is to flood the field to a depth of 5 cm (2 in), then to let the water level drop to 15 cm (6 in) below surface level, as measured by looking into a perforated field water tube sunk into the soil, and then repeating the cycle. Its deep water varieties tolerate flooding to a depth of over 50 centimetres for at least a month. Upland rice is grown without flooding, in hilly or mountainous regions; it is rainfed like wheat or maize.
- Harvesting:
Across Asia, unmilled rice or “paddy” (Indonesian and Malay padi), was traditionally the product of smallholder agriculture, with manual harvesting. Larger farms make use of machines such as combine harvesters to reduce the input of labour. The grain is ready to harvest when the moisture content is 20–25%. Harvesting involves reaping, stacking the cut stalks, threshing to separate the grain, and cleaning by winnowing or screening. Its grain is dried as soon as possible to bring the moisture content down to a level that is safe from mould fungi. Traditional drying relies on the heat of the sun, with the grain spread out on mats or on pavements.
- Commerce:
Production: –
In 2021, its world production was 787 million tonnes, led by China and India with a combined 52% of the total. This placed rice fourth in the list of crops by production, after sugarcane, maize, and wheat. Other major producers were Bangladesh, Indonesia and Vietnam. 90% of world production is from Asia.
| Rice production – 2021 | |
| Country | Millions of tonnes |
| 213 | |
| 195 | |
| 57 | |
| 54 | |
| 44 | |
| 30 | |
| World | 787 |
Yield records: –
The average world yield for rice was 4.7 metric tons per hectare (2.1 short tons per acre), in 2022. Yuan Longping of China’s National Hybrid Rice Research and Development Centre set a world record for rice yield in 1999 at 17.1 metric tons per hectare (7.6 short tons per acre) on a demonstration plot. This employed specially developed hybrid rice and the System of Rice Intensification (SRI), an innovation in rice farming.
Food security: –
It is a major food staple in Asia, Latin America, and some parts of Africa, feeding over half the world’s population. However, a substantial part of the crop can be lost post-harvest through inefficient transportation, storage, and milling. A quarter of the crop in Nigeria is lost after harvest. Storage losses include damage by mould fungi if it is not dried sufficiently. In China, losses in modern metal silos were just 0.2%, compared to 7–13% when rice was stored by rural households.
Eating qualities: –
It is a commonly-eaten food around the world. The varieties of rice are typically classified as short-, medium-, and long-grained. Oryza sativa indica varieties are usually long-grained; Oryza sativa japonica varieties are usually short- or medium-grained. Short-grain rice, with the exception of Spanish Bomba, is usually sticky when cooked, and is suitable for puddings. Thai Jasmine rice is aromatic, and unusually for a long-grain rice has some stickiness, with a soft texture. Indian Basmati rice is very long-grained and aromatic. Italian Arborio rice, used for risotto, is of medium length, oval, and quite sticky. Japanese sushi rice is a sticky short-grain variety.
Nutrition:-
Cooked white rice is 69% water, 29% carbohydrates, 2% protein, and contains negligible fat (table). In a reference serving of 100 grams (3.5 Oz), cooked white rice provides 130 calories of food energy, and contains moderate levels of manganese (18% DV), with no other micronutrients in significant content (all less than 10% of the Daily Value). In 2018, the World Health Organization strongly recommended fortifying rice with iron, and conditionally recommended fortifying it with vitamin A and with folic acid.
Rice and climate change: –
Greenhouse gases from rice production: –
Scientists measuring the greenhouse gas emissions of rice
In 2022, greenhouse gas emissions from its cultivation were estimated at 5.7 billion tonnes CO2eq, representing 1.2% of total emissions. Within the agriculture sector, it produces almost half the greenhouse gas emissions from croplands, some 30% of agricultural methane emissions, and 11% of agricultural nitrous oxide emissions. Methane is released from its fields subject to long-term flooding, as this inhibits the soil from absorbing atmospheric oxygen, resulting in anaerobic fermentation of organic matter in the soil. missions can be limited by planting new varieties, not flooding continuously, and removing straw.