Deepwater rice
Encyclopedia
Deepwater rice is a variety of rice
(Oryza sativa
) grown in flooded conditions with water more than 50 centimetre deep for at least a month.
More than people in South and Southeast Asia rely on deepwater rice for their sustenance. Rice has adapted to deep water in two ways, known as traditional talls and floating rice. Traditional talls are varieties that are grown at water depths of between 50 centimetre and 100 centimetre and have developed to be taller and have longer leaves than standard rice. Floating rice grows in water deeper than 100 centimetre through advanced elongation ability. This means when a field where rice is growing floods, accelerated growth in the internodal
of the stem allows the plant to keep some of its foliage on top of the water. The Indica cultivar
is the main type of deepwater rice, although varieties of Japonica have been found in Burma, Bangladesh
and India.
and Southeast Asia
where more than people rely its production for their livelihood. In South Asia the main area deepwater rice is grown in is the Ganges Brahmaputra basin in India and Bangladesh. In Southeast Asia the main areas of cultivation are in Burma in the Irrawaddy Delta
, in Thailand
in the Chao Phraya and Mekong
in Vietnam
and Cambodia
. In these countries deepwater rice account for more than 25% of the land used to grow rice.
Deepwater rice is cultivated less in West Africa than in Asia with approximately 4700 km² (1,814.7 sq mi). Areas it is grown include the Niger river
basin. Some areas in Ecuador
grow deepwater rice.
s normally around river delta
s and their floodplain
s mainly in backswamp
s and natural levee
s. The nature of the flood is important for success of deepwater rice, with timing and the rate of rise of water affecting survival and crop density. Generally, the flood water comes from rainfall or rises in the water table
. In places with low rainfall, water overspilling from rivers can flood rice producing areas.
conditions before floods arrive. During this stage the plants can also suffer due to competition from weeds. Sudden flooding, where a large volume of water enters the field in a short time, can lead to a high level of seedling death.
Floating rice face additional problems due to the depth and time of the water it grows in. Water conditions such as turbulence
and temperature can adversely affect the crop.
Natural disasters can also damage or destroy deepwater rice crops. Tropical cyclone
s are particularly a problem in Asia. For example, in 2008 Cyclone Nargis
damaged 122,782 hectares of deepwater rice in Burma. If predicted sea level
rises due to climate change
happen, this would affect the pattern of flooding, causing deeper floods over a wider area and eroding the coast.
Rice has adapted to deep water in two ways known as traditional talls and floating rice. Traditional talls are varieties that are grown at water depths of between 50 centimetre and 100 centimetre and have developed to be taller and have longer leaves than standard rice. Floating rice grows in water deeper than 100 centimetre through advanced elongation ability. When submerged this allows it to grow as fast as 25 centimetre a day to reach a length of up to 7 m (23 ft) and survive in water as deep as 4 m (13.1 ft).
The Indica
cultivar
is the main type of deepwater rice, although varieties of Japonica have been found in Burma, Bangladesh and India. Deepwater rice emits the least methane
, a greenhouse gas
, of the wetland rice ecologies, producing approximately three times less than irrigated rice.
of the stem allows the plant to keep some of its foliage on top of the water. The stems are hollow and this allows gas to be exchanged between the plant and the atmosphere. Once the flooding ends the plant is left lying on the ground. The nodes at the top of the plant then start growing upwards towards due to gravitropic
sensitivity.
The elongation is triggered when the plant is submerged through a mechanism involving ethylene
gas. Ethylene is normally produced by plants and diffused
into the air but when floating rice is submerged in water this process is disrupted as the gas moves more slowly into water. This leads to a build up of ethylene in the plant. This triggers the production of a hormone
called gibberellin
which causes the rapid growth in the plant. When the plant reaches the surface the ethylene gas can escape as normal and the rapid growth stops.
Rice
Rice is the seed of the monocot plants Oryza sativa or Oryza glaberrima . As a cereal grain, it is the most important staple food for a large part of the world's human population, especially in East Asia, Southeast Asia, South Asia, the Middle East, and the West Indies...
(Oryza sativa
Oryza sativa
Oryza sativa, commonly known as Asian rice, is the plant species most commonly referred to in English as rice. Oryza sativa is the cereal with the smallest genome, consisting of just 430Mb across 12 chromosomes...
) grown in flooded conditions with water more than 50 centimetre deep for at least a month.
More than people in South and Southeast Asia rely on deepwater rice for their sustenance. Rice has adapted to deep water in two ways, known as traditional talls and floating rice. Traditional talls are varieties that are grown at water depths of between 50 centimetre and 100 centimetre and have developed to be taller and have longer leaves than standard rice. Floating rice grows in water deeper than 100 centimetre through advanced elongation ability. This means when a field where rice is growing floods, accelerated growth in the internodal
Plant stem
A stem is one of two main structural axes of a vascular plant. The stem is normally divided into nodes and internodes, the nodes hold buds which grow into one or more leaves, inflorescence , conifer cones, roots, other stems etc. The internodes distance one node from another...
of the stem allows the plant to keep some of its foliage on top of the water. The Indica cultivar
Cultivar
A cultivar'Cultivar has two meanings as explained under Formal definition. When used in reference to a taxon, the word does not apply to an individual plant but to all those plants sharing the unique characteristics that define the cultivar. is a plant or group of plants selected for desirable...
is the main type of deepwater rice, although varieties of Japonica have been found in Burma, Bangladesh
Bangladesh
Bangladesh , officially the People's Republic of Bangladesh is a sovereign state located in South Asia. It is bordered by India on all sides except for a small border with Burma to the far southeast and by the Bay of Bengal to the south...
and India.
Production
Deepwater rice is a staple food that is grown on around 90000 km² (34,749.2 sq mi) of land. The main areas where it is grown are in SouthSouth Asia
South Asia, also known as Southern Asia, is the southern region of the Asian continent, which comprises the sub-Himalayan countries and, for some authorities , also includes the adjoining countries to the west and the east...
and Southeast Asia
Southeast Asia
Southeast Asia, South-East Asia, South East Asia or Southeastern Asia is a subregion of Asia, consisting of the countries that are geographically south of China, east of India, west of New Guinea and north of Australia. The region lies on the intersection of geological plates, with heavy seismic...
where more than people rely its production for their livelihood. In South Asia the main area deepwater rice is grown in is the Ganges Brahmaputra basin in India and Bangladesh. In Southeast Asia the main areas of cultivation are in Burma in the Irrawaddy Delta
Irrawaddy Delta
The Irrawaddy Delta or Ayeyarwady Delta lies in the Ayeyarwady Region , the lowest expanse of land in Burma that fans out from the limit of tidal influence at Myan Aung to the Bay of Bengal and Andaman Sea, 290 km to the south at the mouth of the Ayeyarwady River...
, in Thailand
Thailand
Thailand , officially the Kingdom of Thailand , formerly known as Siam , is a country located at the centre of the Indochina peninsula and Southeast Asia. It is bordered to the north by Burma and Laos, to the east by Laos and Cambodia, to the south by the Gulf of Thailand and Malaysia, and to the...
in the Chao Phraya and Mekong
Mekong
The Mekong is a river that runs through China, Burma, Laos, Thailand, Cambodia and Vietnam. It is the world's 10th-longest river and the 7th-longest in Asia. Its estimated length is , and it drains an area of , discharging of water annually....
in Vietnam
Vietnam
Vietnam – sometimes spelled Viet Nam , officially the Socialist Republic of Vietnam – is the easternmost country on the Indochina Peninsula in Southeast Asia. It is bordered by China to the north, Laos to the northwest, Cambodia to the southwest, and the South China Sea –...
and Cambodia
Cambodia
Cambodia , officially known as the Kingdom of Cambodia, is a country located in the southern portion of the Indochina Peninsula in Southeast Asia...
. In these countries deepwater rice account for more than 25% of the land used to grow rice.
Deepwater rice is cultivated less in West Africa than in Asia with approximately 4700 km² (1,814.7 sq mi). Areas it is grown include the Niger river
Niger River
The Niger River is the principal river of western Africa, extending about . Its drainage basin is in area. Its source is in the Guinea Highlands in southeastern Guinea...
basin. Some areas in Ecuador
Ecuador
Ecuador , officially the Republic of Ecuador is a representative democratic republic in South America, bordered by Colombia on the north, Peru on the east and south, and by the Pacific Ocean to the west. It is one of only two countries in South America, along with Chile, that do not have a border...
grow deepwater rice.
Cultivation methods
Deepwater rice is grown in tropical monsoon climateTropical monsoon climate
Tropical monsoon climate, occasionally also known as a tropical wet climate or tropical monsoon and trade-wind littoral climate in climate classification, is a relatively rare type of climate that corresponds to the Köppen climate classification category "Am."Tropical monsoon climates have monthly...
s normally around river delta
River delta
A delta is a landform that is formed at the mouth of a river where that river flows into an ocean, sea, estuary, lake, reservoir, flat arid area, or another river. Deltas are formed from the deposition of the sediment carried by the river as the flow leaves the mouth of the river...
s and their floodplain
Floodplain
A floodplain, or flood plain, is a flat or nearly flat land adjacent a stream or river that stretches from the banks of its channel to the base of the enclosing valley walls and experiences flooding during periods of high discharge...
s mainly in backswamp
Backswamp
In geology backswamp is the section of a floodplain where deposits of fine silts and clays settle after a flood. Backswamps usually lie behind a stream's natural levees....
s and natural levee
Levee
A levee, levée, dike , embankment, floodbank or stopbank is an elongated naturally occurring ridge or artificially constructed fill or wall, which regulates water levels...
s. The nature of the flood is important for success of deepwater rice, with timing and the rate of rise of water affecting survival and crop density. Generally, the flood water comes from rainfall or rises in the water table
Water table
The water table is the level at which the submarine pressure is far from atmospheric pressure. It may be conveniently visualized as the 'surface' of the subsurface materials that are saturated with groundwater in a given vicinity. However, saturated conditions may extend above the water table as...
. In places with low rainfall, water overspilling from rivers can flood rice producing areas.
Issues
When seeds are sown directly into the ground the seeds and young plants can be damaged by droughtDrought
A drought is an extended period of months or years when a region notes a deficiency in its water supply. Generally, this occurs when a region receives consistently below average precipitation. It can have a substantial impact on the ecosystem and agriculture of the affected region...
conditions before floods arrive. During this stage the plants can also suffer due to competition from weeds. Sudden flooding, where a large volume of water enters the field in a short time, can lead to a high level of seedling death.
Floating rice face additional problems due to the depth and time of the water it grows in. Water conditions such as turbulence
Turbulence
In fluid dynamics, turbulence or turbulent flow is a flow regime characterized by chaotic and stochastic property changes. This includes low momentum diffusion, high momentum convection, and rapid variation of pressure and velocity in space and time...
and temperature can adversely affect the crop.
Natural disasters can also damage or destroy deepwater rice crops. Tropical cyclone
Tropical cyclone
A tropical cyclone is a storm system characterized by a large low-pressure center and numerous thunderstorms that produce strong winds and heavy rain. Tropical cyclones strengthen when water evaporated from the ocean is released as the saturated air rises, resulting in condensation of water vapor...
s are particularly a problem in Asia. For example, in 2008 Cyclone Nargis
Cyclone Nargis
Cyclone Nargis , was a strong tropical cyclone that caused the worst natural disaster in the recorded history of Burma. The cyclone made landfall in Burma on Friday, May 2, 2008, causing catastrophic destruction and at least 138,000 fatalities...
damaged 122,782 hectares of deepwater rice in Burma. If predicted sea level
Current sea level rise
Current sea level rise potentially impacts human populations and the wider natural environment . Global average sea level rose at an average rate of around 1.8 mm per year over 1961 to 2003 and at an average rate of about 3.1 mm per year from 1993 to 2003...
rises due to climate change
Climate change
Climate change is a significant and lasting change in the statistical distribution of weather patterns over periods ranging from decades to millions of years. It may be a change in average weather conditions or the distribution of events around that average...
happen, this would affect the pattern of flooding, causing deeper floods over a wider area and eroding the coast.
Characteristics
Deepwater rice is rice grown in flooded conditions with water more than 50 centimetre deep for at least a month.Rice has adapted to deep water in two ways known as traditional talls and floating rice. Traditional talls are varieties that are grown at water depths of between 50 centimetre and 100 centimetre and have developed to be taller and have longer leaves than standard rice. Floating rice grows in water deeper than 100 centimetre through advanced elongation ability. When submerged this allows it to grow as fast as 25 centimetre a day to reach a length of up to 7 m (23 ft) and survive in water as deep as 4 m (13.1 ft).
The Indica
Indica
Indica may refer to:Historical ethnographic accounts of India* Indica , Arrian's account of Nearchus' voyage from India* Indica , the Biruni's account of his travels in South Asia...
cultivar
Cultivar
A cultivar'Cultivar has two meanings as explained under Formal definition. When used in reference to a taxon, the word does not apply to an individual plant but to all those plants sharing the unique characteristics that define the cultivar. is a plant or group of plants selected for desirable...
is the main type of deepwater rice, although varieties of Japonica have been found in Burma, Bangladesh and India. Deepwater rice emits the least methane
Methane
Methane is a chemical compound with the chemical formula . It is the simplest alkane, the principal component of natural gas, and probably the most abundant organic compound on earth. The relative abundance of methane makes it an attractive fuel...
, a greenhouse gas
Greenhouse gas
A greenhouse gas is a gas in an atmosphere that absorbs and emits radiation within the thermal infrared range. This process is the fundamental cause of the greenhouse effect. The primary greenhouse gases in the Earth's atmosphere are water vapor, carbon dioxide, methane, nitrous oxide, and ozone...
, of the wetland rice ecologies, producing approximately three times less than irrigated rice.
Floating rice adaptation
Floating rice is planted in dry ground and allowed to establish as young plants. The area becomes flooded which triggers the rice's elongation ability. This means when a field where rice is growing floods, accelerated growth in the internodesPlant stem
A stem is one of two main structural axes of a vascular plant. The stem is normally divided into nodes and internodes, the nodes hold buds which grow into one or more leaves, inflorescence , conifer cones, roots, other stems etc. The internodes distance one node from another...
of the stem allows the plant to keep some of its foliage on top of the water. The stems are hollow and this allows gas to be exchanged between the plant and the atmosphere. Once the flooding ends the plant is left lying on the ground. The nodes at the top of the plant then start growing upwards towards due to gravitropic
Gravitropism
Gravitropism is a turning or growth movement by a plant or fungus in response to gravity. Charles Darwin was one of the first to scientifically document that roots show positive gravitropism and stems show negative gravitropism. That is, roots grow in the direction of gravitational pull and stems...
sensitivity.
The elongation is triggered when the plant is submerged through a mechanism involving ethylene
Ethylene
Ethylene is a gaseous organic compound with the formula . It is the simplest alkene . Because it contains a carbon-carbon double bond, ethylene is classified as an unsaturated hydrocarbon. Ethylene is widely used in industry and is also a plant hormone...
gas. Ethylene is normally produced by plants and diffused
Diffusion
Molecular diffusion, often called simply diffusion, is the thermal motion of all particles at temperatures above absolute zero. The rate of this movement is a function of temperature, viscosity of the fluid and the size of the particles...
into the air but when floating rice is submerged in water this process is disrupted as the gas moves more slowly into water. This leads to a build up of ethylene in the plant. This triggers the production of a hormone
Hormone
A hormone is a chemical released by a cell or a gland in one part of the body that sends out messages that affect cells in other parts of the organism. Only a small amount of hormone is required to alter cell metabolism. In essence, it is a chemical messenger that transports a signal from one...
called gibberellin
Gibberellin
Gibberellins are plant hormones that regulate growth and influence various developmental processes, including stem elongation, germination, dormancy, flowering, sex expression, enzyme induction, and leaf and fruit senescence....
which causes the rapid growth in the plant. When the plant reaches the surface the ethylene gas can escape as normal and the rapid growth stops.