Where is rice grown?
Rice is grown in more than a hundred countries, with a total harvested area in 2009 of approximately 158 million hectares, producing more than 700 million tons annually (470 million tons of milled rice). About 90% of the rice in the world is grown in Asia (nearly 640 million tons). Sub-Saharan Africa produces about 19 million tons and Latin America some 25 million tons. In Asia and sub-Saharan Africa, almost all rice is grown on small farms of 0.5−3 hectares.
Where rice is grown around the world - showing the three major rice growing environments.
Rice yields range from less than 1 ton per hectare under very poor rainfed conditions to more than 10 t/ha in intensive temperate irrigated systems. Small, and in many areas shrinking, farm sizes account for the low incomes of rice farm families.
Rice grows in a wide range of environments and is productive in many situations where other crops would fail. Rice-growing environments are based on their hydrological characteristics and include irrigated, rainfed lowland, and rainfed upland.
Irrigated rice environments
Worldwide, about 80 million ha of irrigated lowland rice provide 75% of the world’s rice production. These systems remain the most important rice production systems for food security, particularly in Asian countries.
Irrigated rice is grown in bunded fields with ensured irrigation for one or more crops a year. Farmers generally try to maintain 5–10 centimeters (cm) of water (“floodwater”) on the field. By and large, irrigated rice farms are small, with the majority in the 0.5 to 2 ha range. In many humid tropical and subtropical areas, irrigated rice is grown as a monoculture with two or even three crops a year.
Significant areas of irrigated rice are also grown in rotation with a range of other crops, including about 20 million ha of rice-wheat systems. Irrigated rice receives about 40% of the world’s irrigation water and 30% of the world’s developed freshwater resources. At present, average irrigated yields are about 5.4 t/ha. In temperate climatic regions, a single irrigated rice crop is grown per year, with high yield that can reach 8–10 t/ha or more.
Rainfed lowland environments
Rainfed lowland rice is grown in bunded fields that are flooded with rainwater for at least part of the cropping season. About 60 million ha of rainfed lowlands supply about 20% of the world’s rice production. Rainfed rice environments experience multiple abiotic stresses and high uncertainty in timing, duration, and intensity of rainfall.
Some 27 million ha of rainfed rice are frequently affected by drought. Up to 20 million ha may suffer from uncontrolled flooding, ranging from flash floods of relatively short duration to deepwater areas that may be submerged under more than 100 cm of water for a few months. Deepwater rice and floating rice are found in flood-prone environments, where the fields suffer periodically from such excess water. Further constraints arise from the widespread incidence of problem soils with poor physical and chemical properties. Salinity is widespread in coastal areas.
Rainfed lowland rice predominates in areas of greatest poverty: South Asia, parts of Southeast Asia, and essentially all of Africa. Because the environments are so difficult and yields so unreliable, farmers rarely apply fertilizer and tend to not grow improved varieties. Thus, yields are very low (1–2.5 t/ha) and farm families remain trapped in poverty.
Rainfed upland environments
Upland rice is grown under dryland conditions in mixed farming systems without irrigation and without puddling. It covers about 14 million ha but, because of many constraints that cause low yields (typically only about 1 t/ha), it contributes only 4% of the world’s total rice production.
Upland environments are highly variable, with climates ranging from humid to subhumid, soils from relatively fertile to highly infertile, and topography from flat to steeply sloping. With low population density and limited market access, shifting cultivation with long (more than 15 years) fallow periods was historically the dominant land-use system. Some 70% of Asia’s upland rice areas have made the transition to permanent systems where rice is grown every year and is closely integrated with other crops and livestock.
In Central and West Africa, the rice belt of Africa, upland areas represent about 40% of the area under rice cultivation and employ about 70% of the region’s rice farmers. As market access remains limited, most of the world’s upland rice farmers tend to be self-sufficient by producing a range of agricultural outputs. Poverty is widespread in these upland areas.
Rice goes through a series of processes before finally reaching your dinner table. Rice production can generally be divided into the following stages:
- Seed selection
- Land preparation
- Crop establishment
- Water management
- Nutrient management
- Crop health
Choosing a suitable variety of rice to grow that suits the environment it will be grown in and ensuring the seed choosen of that variety is of the highest possible quality is the essential first step in rice production.
Seed is a living product that must be grown, harvested, and processed correctly to maximize its viability and subsequent crop productivity. For the yield potential of any rice variety to be realized, good quality seed must be sown. Good quality seed can increase yields by 5-20%. The extent of this increase is directly proportional to the quality of seed that is being sown.
Good seed is pure (of the chosen variety), full and uniform in size, viable (more than 80% germination with good seedling vigor), and free of weed seeds, seed-borne diseases, pathogens, insects, or other matter.
Using good seed leads to lower seeding rates, higher crop emergence, reduced replanting, more uniform plant stands, and more vigorous early crop growth. Vigorous growth in early stages reduces weed problems and increases crop resistance to insect pests and diseases. All of these factors contribute to higher yields and more productive rice farms.
The aim of land preparation for rice production is to place the soil in the best physical condition for crop growth and to ensure that the soil surface is level.
Tillage requirements vary according to the cropping system as what may be desirable for one may be totally inappropriate for another. A good example is the contrast between lowland and upland systems. Typically for lowland rice, fields are puddled in part to destroy structure and develop a hard pan to reduce water loss through deep percolation. Such a loss of structure and the formation of a physical barrier are totally undesirable in an upland situation.
Land preparation involves plowing and harrowing to "till" or dig-up, mix, and overturn the soil, and leveling.
Tillage is done to a depth so plants can develop a root system which will physically support the plant and also allow the extraction of sufficient moisture and nutrients so yield potentials can be realized. Tillage also helps with weed control. Farmers can till the land tehmselves using hoes and other equipment or they can be assisted by draft animals, such as buffalo, or tractors and other machinery.
Land leveling follows tillage and is primarily done to reduce water wastage. Uneven land results in uneven water coverage meaning more water is needed to ensure all parts of the paddy are wet in preparation for the establishment of the rice seed or seedlings. Effective land leveling will improve crop establishment and care, reduce the amount of effort required to manage the crop, and will increase both grain quality and yields.
The two main practices of establishing rice plants are transplanting and direct seeding.
Transplanting rice seedlings is the most popular way
in Asia to establish a crop, but it is back-breaking work.
Transplanting is the most popular plant establishment technique across Asia. Transplanting is when pre-germinated seedlings are transferred from a seedbed to the wet field. It requires less seed and is an effective method to control weeds, but requires more labor.
Prior to transplanting, seedlings are established in a separate nursery area. They are grown here for between 20 and 80 days before they are transplanted to the field. Seedlings may be transplanted by either machine or hand.
Direct seeding is when dry seed or pre-germinated seeds and seedlings are broadcast by hand or planted by machine. In rainfed and deepwater ecosystems, dry seed is manually broadcast onto the soil surface and then incorporated either by ploughing or by harrowing while the soil is still dry. In irrigated areas, seed is normally pre-germinated prior to broadcasting.
Cultivated rice has a semi-aquatic ancestry and is therefore extremely sensitive to water shortages. When the soil water content drops below saturation, most rice varieties develop symptoms of water stress. Sound water management practices are needed to use water wisely and maximize rice yield.
To ensure sufficient water, most rice farmers aim to maintain flooded conditions in their field. This is especially true for lowland rice. Good water management in lowland rice focuses on practices that conserve water (by eliminating the unproductive water flows of seepage, percolation, and evaporation) while ensuring sufficient water for the crop.
In rainfed environments when optimal amounts of water may not be available for rice production, a suite of options are available to help farmers cope with different degrees and forms of water scarcity. It includes sound land preparation and pre-planting activities followed by techniques such as saturated soil culture, alternate wetting and drying, raised beds, mulching, and use of aerobic rice that can cope with dryer conditions.
Ensuring that the rice plant gets the exact nutrients it needs to grow is of great importance. This is because each growth stage of the rice plant has specific nutrient needs.
The unique properties of flooded soils make rice different from any other crop. Because of prolonged flooding in rice fields, farmers are able to conserve soil organic matter and also receive free input of nitrogen from biological sources. This biological fixation amounts to enough to help ensure a stable yield of about 3 tons per hectare per crop in the absence of applied nitrogen fertilizer.
If higher yields are the target then the rice will need more nutrients.
Site-specific nutrient management provides scientific principles for optimally supplying rice with essential nutrients. It enables rice farmers to tailor nutrient management to the specific conditions of their field, and it provides a framework for nutrient best management practices for rice.
The rice plant has a wide array of ‘enemies’ in the field. These include rodents, harmful insects, viruses, diseases, and weeds. Farmers use many different strategies to control these pests and diseases to maintain crop health.
Best practice in maintaining crop health revolves around an understanding of the interactions among pests, natural enemies, host plants, other organisms, and the environment to determine what if any pest management may be necessary.
Avoiding conditions that allow pests to adapt and thrive in a particular ecosystem helps to identify weak links in the pests' life cycle and therefore what factors can be manipulated to manage them. Retaining natural ecosystems such that predators and natural enemies of pests and diseases are kept in abundance can also help keep pest numbers down.
Farmers manage weeds through water management and land preparation, by hand weeding, and in some cases herbcide application.
Harvesting is the process of collecting the mature rice crop from the field. Depending on the variety, a rice crop usually reaches maturity at around 115-120 days after crop establishment. Harvesting activities include cutting, stacking, handling, threshing, cleaning, and hauling. Good harvesting methods help maximize grain yield and minimize grain damage and deterioration.
Harvesting can be done manually or mechanically.
Manual harvesting is common across Asia It involves cutting the rice crop with simple hand tools like sickles and knives. Manual harvesting is very effective when a crop has lodged or fallen over, however it is labor intensive. Manual harvesting requires 40 to 80 man-hours per hectare and it takes additional labor to manually collect and haul the harvested crop.
Mechanical harvesting using reapers or combine harvesters is the other option, but not so common due to the availability and cost of machinery.
Following cutting the rice must be threshed to separate the grain from the stalk and cleaned. These processes can also be done by hand or machine.
After harvest, the rice grain undergoes a number of processes depending on how it will be used. Such methods include, drying, storing, milling, and processing.
Drying is the process that reduces grain moisture content to a safe level for storage. Drying is the most critical operation after harvesting a rice crop. Delays in drying, incomplete drying or ineffective drying will reduce grain quality and result in losses.
Storing grain is done to reduce grain loss to weather, moisture, rodents, birds, insects and micro-organisms.
Milling is a crucial step in post-production of rice. The basic objective of a rice milling system is to remove the husk and the bran layers, and produce an edible, white rice kernel that is sufficiently milled and free of impurities.
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