Aeroponics is the process of growing plants in an air or mist environment without the use of soil or an aggregate medium. The word "aeroponic" is derived from the Greek meanings of aer and ponos. Aeroponic culture differs from both conventional hydroponics, in-vitro growing. Unlike hydroponics, which uses a liquid nutrient solution as a growing medium and essential minerals to sustain plant growth, it is sometimes considered a type of hydroponics, since water is used in aeroponics to transmit nutrients. The basic principle of aeroponic growing is to grow plants suspended in a closed or semi-closed environment by spraying the plant's dangling roots and lower stem with an atomized or sprayed, nutrient-rich water solution; the leaves and crown called the canopy, extend above. The roots of the plant are separated by the plant support structure. Closed-cell foam is compressed around the lower stem and inserted into an opening in the aeroponic chamber, which decreases labor and expense. Ideally, the environment is kept free from pests and disease so that the plants may grow healthier and more than plants grown in a medium.
However, since most aeroponic environments are not closed off to the outside and disease may still cause a threat. Controlled environments advance plant development, growth and fruiting for any given plant species and cultivars. Due to the sensitivity of root systems, aeroponics is combined with conventional hydroponics, used as an emergency "crop saver" – backup nutrition and water supply – if the aeroponic apparatus fails. High-pressure aeroponics is defined as delivering nutrients to the roots via 20–50 micrometre mist heads using a high-pressure diaphragm pump. Air cultures optimize access to air for successful plant growth. Materials and devices which hold and support the aeroponic grown plants must be devoid of disease or pathogens. A distinction of a true aeroponic culture and apparatus is that it provides plant support features that are minimal. Minimal contact between a plant and support structure allows for 100% of the plant to be in air. Long-term aeroponic cultivation requires the root systems to be free of constraints surrounding the stem and root systems.
Physical contact is minimized so that it does not hinder natural growth and root expansion or access to pure water, air exchange and disease-free conditions. Oxygen in the rhizosphere is necessary for healthy plant growth; as aeroponics is conducted in air combined with micro-droplets of water any plant can grow to maturity in air with a plentiful supply of oxygen and nutrients. Some growers favor aeroponic systems over other methods of hydroponics because the increased aeration of nutrient solution delivers more oxygen to plant roots, stimulating growth and helping to prevent pathogen formation. Clean air supplies oxygen, an excellent purifier for plants and the aeroponic environment. For natural growth to occur, the plant must have unrestricted access to air. Plants must be allowed to grow in a natural manner for successful physiological development; the more confining the plant support becomes, the greater incidence of increasing disease pressure of the plant and the aeroponic system. Some researchers have used aeroponics to study the effects of root zone gas composition on plant performance.
Soffer and Burger studied the effects of dissolved oxygen concentrations on the formation of adventitious roots in what they termed “aero-hydroponics.” They utilized a 3-tier hydro and aero system, in which three separate zones were formed within the root area. The ends of the roots were submerged in the nutrient reservoir, while the middle of the root section received nutrient mist and the upper portion was above the mist, their results showed that dissolved O2 is essential to root formation, but went on to show that for the three O2 concentrations tested, the number of roots and root length were always greater in the central misted section than either the submersed section or the un-misted section. At the lowest concentration, the misted section rooted successfully. Plants in a true aeroponic apparatus have 100% access to the CO2 concentrations ranging from 450 ppm to 780 ppm for photosynthesis. At one mile above sea level, the CO2 concentration in the air is 450 ppm during daylight. At night, the CO2 level will rise to 780 ppm.
Lower elevations will have higher levels. In any case, the air culture apparatus offers the ability for plants to have full access to all of the available CO2 in the air for photosynthesis. Growing under lights during the evening allows aeroponics to benefit from the natural occurrence. Aeroponics can limit disease transmission since plant-to-plant contact is reduced and each spray pulse can be sterile. In the case of soil, aggregate, or other media, disease can spread throughout the growth media, infecting many plants. In most greenhouses, these solid media require sterilization after each crop and, in many cases, they are discarded and replaced with fresh, sterile media. A distinct advantage of aeroponic technology is that if a particular plant does become diseased, it can be removed from the plant support structure without disrupting or infecting the other plants. Due to the disease-free environment, unique to aeroponics, many plants can grow at higher density when compared to more traditional forms of cultivation.
Frederick Law Olmsted
Frederick Law Olmsted was an American landscape architect, social critic, public administrator. He is popularly considered to be the father of American landscape architecture. Olmsted was famous for co-designing many well-known urban parks with his senior partner Calvert Vaux, including Central Park in New York City and Cadwalader Park in Trenton. Other projects that Olmsted was involved in include the country's first and oldest coordinated system of public parks and parkways in Buffalo, New York. In Chicago his projects include: Jackson Park. In Washington, D. C. he worked on the landscape surrounding the United States Capitol building. The quality of Olmsted's landscape architecture was recognized by his contemporaries, who showered him with prestigious commissions. Daniel Burnham said of him, "He paints with wooded slopes, his work in Central Park in New York City, set a standard of excellence that continues to influence landscape architecture in the United States. He was an early and important activist in the conservation movement, including work at Niagara Falls.
Olmsted was born in Hartford, Connecticut, on April 26, 1822. His father, John Olmsted, was a prosperous merchant who took a lively interest in nature and places, his mother, Charlotte Law Olmsted, died before his fourth birthday. His father remarried in 1827 to Mary Ann Bull, who shared her husband's strong love of nature and had a more cultivated taste; when the young Olmsted was ready to enter Yale College, sumac poisoning weakened his eyes, so he gave up college plans. After working as an apprentice seaman and journalist, Olmsted settled on a 125-acre farm in January 1848 on the south shore of Staten Island NY, a farm which his father helped him acquire; this farm named the Akerly Homestead, was renamed Tosomock Farm by Olmsted. It was renamed "The Woods of Arden" by owner Erastus Wiman. On June 13, 1859, Olmsted married the widow of his brother John. Daniel Fawcett Tiemann, the mayor of New York, officiated the wedding, he adopted John Charles Olmsted, Charlotte Olmsted and Owen Olmsted. Frederick and Mary had two children together who survived infancy: a daughter, a son Frederick Law Olmsted Jr.
Their first child, John Theodore Olmsted, was born on June 13, 1860, died in infancy. Olmsted had a significant career in journalism. In 1850 he traveled to England to visit public gardens, where he was impressed by Joseph Paxton's Birkenhead Park, he subsequently wrote and published Walks and Talks of an American Farmer in England in 1852. This supported his getting additional work. Interested in the slave economy, he was commissioned by the New York Daily Times to embark on an extensive research journey through the American South and Texas from 1852 to 1857, his dispatches to the Times were collected into three volumes which remain vivid first-person social documents of the pre-war South. A one-volume abridgment and Explorations in the Cotton Kingdom, was published during the first six months of the American Civil War at the suggestion of Olmsted's English publisher. To this he wrote a new introduction in which he stated explicitly his views on the effect of slavery on the economy and social conditions of the southern states.
My own observation of the real condition of the people of our Slave States, gave me... an impression that the cotton monopoly in some way did them more harm than good. He argued that slavery had made the slave states inefficient and backward both economically and socially; the profits of slavery fell to no more than 8,000 owners of large plantations.
New Jersey is a state in the Mid-Atlantic and Northeastern regions of the United States. It is located on a peninsula, bordered on the north and east by the state of New York along the extent of the length of New York City on its western edge. New Jersey is the fourth-smallest state by area but the 11th-most populous, with 9 million residents as of 2017, the most densely populated of the 50 U. S. states. New Jersey lies within the combined statistical areas of New York City and Philadelphia. New Jersey was the second-wealthiest U. S. state by median household income as of 2017. New Jersey was inhabited by Native Americans for more than 2,800 years, with historical tribes such as the Lenape along the coast. In the early 17th century, the Dutch and the Swedes founded the first European settlements in the state; the English seized control of the region, naming it the Province of New Jersey after the largest of the Channel Islands and granting it as a colony to Sir George Carteret and John Berkeley, 1st Baron Berkeley of Stratton.
New Jersey was the site of several decisive battles during the American Revolutionary War in the 18th century. In the 19th century, factories in cities, Paterson, Trenton, Jersey City, Elizabeth helped to drive the Industrial Revolution. New Jersey's geographic location at the center of the Northeast megalopolis, between Boston and New York City to the northeast, Philadelphia and Washington, D. C. to the southwest, fueled its rapid growth through the process of suburbanization in the second half of the 20th century. In the first decades of the 21st century, this suburbanization began reverting with the consolidation of New Jersey's culturally diverse populace toward more urban settings within the state, with towns home to commuter rail stations outpacing the population growth of more automobile-oriented suburbs since 2008. Around 180 million years ago, during the Jurassic Period, New Jersey bordered North Africa; the pressure of the collision between North America and Africa gave rise to the Appalachian Mountains.
Around 18,000 years ago, the Ice Age resulted in glaciers. As the glaciers retreated, they left behind Lake Passaic, as well as many rivers and gorges. New Jersey was settled by Native Americans, with the Lenni-Lenape being dominant at the time of contact. Scheyichbi is the Lenape name for the land, now New Jersey; the Lenape were several autonomous groups that practiced maize agriculture in order to supplement their hunting and gathering in the region surrounding the Delaware River, the lower Hudson River, western Long Island Sound. The Lenape society was divided into matrilinear clans; these clans were organized into three distinct phratries identified by their animal sign: Turtle and Wolf. They first encountered the Dutch in the early 17th century, their primary relationship with the Europeans was through fur trade; the Dutch became the first Europeans to lay claim to lands in New Jersey. The Dutch colony of New Netherland consisted of parts of modern Middle Atlantic states. Although the European principle of land ownership was not recognized by the Lenape, Dutch West India Company policy required its colonists to purchase the land that they settled.
The first to do so was Michiel Pauw who established a patronship called Pavonia in 1630 along the North River which became the Bergen. Peter Minuit's purchase of lands along the Delaware River established the colony of New Sweden; the entire region became a territory of England on June 24, 1664, after an English fleet under the command of Colonel Richard Nicolls sailed into what is now New York Harbor and took control of Fort Amsterdam, annexing the entire province. During the English Civil War, the Channel Island of Jersey remained loyal to the British Crown and gave sanctuary to the King, it was from the Royal Square in Saint Helier that Charles II of England was proclaimed King in 1649, following the execution of his father, Charles I. The North American lands were divided by Charles II, who gave his brother, the Duke of York, the region between New England and Maryland as a proprietary colony. James granted the land between the Hudson River and the Delaware River to two friends who had remained loyal through the English Civil War: Sir George Carteret and Lord Berkeley of Stratton.
The area was named the Province of New Jersey. Since the state's inception, New Jersey has been characterized by religious diversity. New England Congregationalists settled alongside Scots Presbyterians and Dutch Reformed migrants. While the majority of residents lived in towns with individual landholdings of 100 acres, a few rich proprietors owned vast estates. English Quakers and Anglicans owned large landholdings. Unlike Plymouth Colony and other colonies, New Jersey was populated by a secondary wave of immigrants who came from other colonies instead of those who migrated directly from Europe. New Jersey remained agrarian and rural throughout the colonial era, commercial farming developed sporadically; some townships, such as Burlington on the Delaware River and Perth Amboy, emerged as important ports for shipping to New York City and Philadelphia. The colony's fertile lands and tolerant religious policy drew more settlers, New Jersey's population had increased to 120,000 by 1775. Settlement for the first 10 years of English rule took place along Hackensack River and Arthur Kill –
Urbanization refers to the population shift from rural areas to urban areas, the gradual increase in the proportion of people living in urban areas, the ways in which each society adapts to this change. It is predominantly the process by which towns and cities are formed and become larger as more people begin living and working in central areas. Although the two concepts are sometimes used interchangeably, urbanization should be distinguished from urban growth: urbanization is "the proportion of the total national population living in areas classed as urban", while urban growth refers to "the absolute number of people living in areas classed as urban"; the United Nations projected that half of the world's population would live in urban areas at the end of 2008. It is predicted that by 2050 about 64% of the developing world and 86% of the developed world will be urbanized; that is equivalent to 3 billion urbanites by 2050, much of which will occur in Africa and Asia. Notably, the United Nations has recently projected that nearly all global population growth from 2017 to 2030 will be by cities, about 1.1 billion new urbanites over the next 13 years.
Urbanization is relevant to a range of disciplines, including urban planning, sociology, architecture and public health. The phenomenon has been linked to modernization, industrialization, the sociological process of rationalization. Urbanization can be seen as a specific condition at a set time, or as an increase in that condition over time. So urbanization can be quantified either in terms of, the level of urban development relative to the overall population, or as the rate at which the urban proportion of the population is increasing. Urbanization creates enormous social and environmental changes, which provide an opportunity for sustainability with the “potential to use resources more efficiently, to create more sustainable land use and to protect the biodiversity of natural ecosystems.”Urbanization is not a modern phenomenon, but a rapid and historic transformation of human social roots on a global scale, whereby predominantly rural culture is being replaced by predominantly urban culture.
The first major change in settlement patterns was the accumulation of hunter-gatherers into villages many thousand years ago. Village culture is characterized by common bloodlines, intimate relationships, communal behavior, whereas urban culture is characterized by distant bloodlines, unfamiliar relations, competitive behavior; this unprecedented movement of people is forecast to continue and intensify during the next few decades, mushrooming cities to sizes unthinkable only a century ago. As a result, the world urban population growth curve has up till followed a quadratic-hyperbolic pattern. Today, in Asia the urban agglomerations of Osaka, Jakarta, Shanghai, Manila and Beijing are each home to over 20 million people, while Delhi and Tokyo are forecast to approach or exceed 40 million people. Cities such as Tehran, Mexico City, São Paulo, New York City and Cairo are, or soon will be, home to over 10 million people each. From the development of the earliest cities in Mesopotamia and Egypt until the 18th century, an equilibrium existed between the vast majority of the population who engaged in subsistence agriculture in a rural context, small centres of populations in the towns where economic activity consisted of trade at markets and manufactures on a small scale.
Due to the primitive and stagnant state of agriculture throughout this period, the ratio of rural to urban population remained at a fixed equilibrium. However, a significant increase in the percentage of the global urban population can be traced in the 1st millennium BCE. Another significant increase can be traced to Mughal India, where 15% of its population lived in urban centers during the 16th–17th centuries, higher than in Europe at the time. In comparison, the percentage of the European population living in cities was 8–13% in 1800. With the onset of the British agricultural and industrial revolution in the late 18th century, this relationship was broken and an unprecedented growth in urban population took place over the course of the 19th century, both through continued migration from the countryside and due to the tremendous demographic expansion that occurred at that time. In England and Wales, the proportion of the population living in cities with more than 20,000 people jumped from 17% in 1801 to 54% in 1891.
Moreover, adopting a broader definition of urbanization, we can say that while the urbanized population in England and Wales represented 72% of the total in 1891, for other countries the figure was 37% in France, 41% in Prussia and 28% in the United States. As labourers were freed up from working the land due to higher agricultural productivity they converged on the new industrial cities like Manchester and Birmingham which were experiencing a boom in commerce and industry. Growing trade around the world allowed cereals to be imported from North America and refrigerated meat from Australasia and South America. Spatially, cities expanded due to the development of public transport systems, which facilitated commutes of longer distances to the city centre for the working class. Urbanization spread across the Western world and, since the 1950s, it has begun to take hold in the developing world as well. At the turn of the 20th century, just 15% of the world population lived in cities. According to the UN, the year 2007 witnessed the turning point when more than 50% of the world population were living in cities, for the first time in human history.
Yale University in June 2016 published urbanization
Addis Ababa is the capital and largest city of Ethiopia. According to the 2007 census, the city has a population of 2,739,551 inhabitants; as a chartered city, Addis Ababa has the status of a state. It is where the African Union is headquartered and where its predecessor the Organisation of African Unity was based, it hosts the headquarters of the United Nations Economic Commission for Africa, as well as various other continental and international organizations. Addis Ababa is therefore referred to as "the political capital of Africa" for its historical and political significance for the continent; the city lies a few miles west of the East African Rift. The city is populated by people from different regions of Ethiopia, it is home to Addis Ababa University. Entoto is one of a handful of sites put forward as a possible location for a medieval imperial capital known as Barara; this permanent fortified city was established during the early-to-mid 15th century, it served as the main residence of several successive emperors up to the early 16th-century reign of Lebna Dingel.
The city was depicted standing between Mounts Zikwala and Menegasha on a map drawn by the Italian cartographer Fra Mauro in around 1450, it was razed and plundered by Ahmed Gragn while the imperial army was trapped on the south of the Awash River in 1529, an event witnessed and documented two years by the Yemeni writer Arab-Faqih. The suggestion that Barara was located on Mount Entoto is supported by the recent discovery of a large medieval town overlooking Addis Ababa located between rock-hewn Washa Mikael and the more modern church of Entoto Maryam, founded in the late 19th century by Emperor Menelik. Dubbed the Pentagon, the 30-hectare site incorporates a castle with 12 towers, along with 520 meters of stone walls measuring up to 5-meter high; the site of Addis Ababa was chosen by Empress Taytu Betul and the city was founded in 1886 by Emperor Menelik II. Menelik, as a King of the Shewa province, had found Mount Entoto a useful base for military operations in the south of his realm, in 1879 he visited the reputed ruins of a medieval town and an unfinished rock church that showed proof of the medieval empire's capital in the area before the campaigns of Ahmad ibn Ibrihim.
His interest in the area grew when his wife Taytu began work on a church on Mount Entoto, Menelik endowed a second church in the area. However, the immediate area did not encourage the founding of a town for lack of firewood and water, so settlement began in the valley south of the mountain in 1886. Taytu built a house for herself near the "Filwoha" hot mineral springs, where she and members of the Showan Royal Court liked to take mineral baths. Other nobility and their staff and households settled in the vicinity, Menelik expanded his wife's house to become the Imperial Palace which remains the seat of government in Addis Ababa today; the name changed to Addis Ababa and became Ethiopia's capital when Menelik II became Emperor of Ethiopia. The town grew by bounds. One of Emperor Menelik's contributions that are still visible today is the planting of numerous eucalyptus trees along the city streets. Following all the major engagements of their invasion, Italian troops from the colony of Eritrea entered Addis Ababa on 5 May 1936.
Along with Dire Dawa, the city had been spared the aerial bombardment practiced elsewhere and its railway to Djibouti remained intact. After the occupation the city served as the Duke of Aosta's capital for unified Italian East Africa until 1941, when it was abandoned in favor of Amba Alagi and other redoubts during the Second World War's East African Campaign; the city was liberated by Major Orde Wingate and negus Haile Selassie for Ethiopian Gideon Force and Ethiopian resistance in time to permit Emperor Haile Selassie's return on 5 May 1941, five years to the day after he had left. Following reconstruction, Haile Selassie helped form the Organisation of African Unity in 1963 and invited the new organization to keep its headquarters in Addis Ababa; the OAU was dissolved in 2002 and replaced by the African Union, headquartered in the city. The United Nations Economic Commission for Africa has its headquarters in Addis Ababa. Addis Ababa was the site of the Council of the Oriental Orthodox Churches in 1965.
Ethiopia has been called the original home of mankind because of various humanoid fossil discoveries like the Australopithecine Lucy. Northeastern Africa, the Afar region in particular, was the central focus of these claims until recent DNA evidence suggested origins in south central Ethiopian regions like present-day Addis Ababa. After analysing the DNA of 1,000 people around the world and other scientists claimed people spread from what is now Addis Ababa 100,000 years ago; the research indicated that genetic diversity decreases the farther one's ancestors traveled from Addis Ababa, Ethiopia. Addis Ababa lies at an elevation of 2,200 metres and is a grassland biome, located at 9°1′48″N 38°44′24″E; the city forms part of the watershed for the Awash. From its lowest point, around Bole International Airport, at 2,326 metres above sea level in the southern periphery, Addis Ababa rises to over 3,000 metres in the Entoto Mountains to the north; the city is divided into 10 boroughs, called subcities, 99 wards.
The 10 subc
Germination is the process by which an organism grows from a seed or similar structure. The most common example of germination is the sprouting of a seedling from a seed of an angiosperm or gymnosperm. In addition, the growth of a sporeling from a spore, such as the spores of hyphae from fungal spores, is germination. Thus, in a general sense, germination can be thought of as anything expanding into greater being from a small existence or germ. Most seeds do not need sunlight to germinate but some seeds such as sunflower seeds, mustard seeds and blosnian seeds need sunlight to germinate. Experiments were carried out to prove this. Germination is the growth of a plant contained within a seed; the seed of a vascular plant is a small package produced in a fruit or cone after the union of male and female reproductive cells. All developed seeds contain an embryo and, in most plant species some store of food reserves, wrapped in a seed coat; some plants produce varying numbers of seeds. Dormant seeds are ripe seeds that do not germinate because they are subject to external environmental conditions that prevent the initiation of metabolic processes and cell growth.
Under proper conditions, the seed begins to germinate and the embryonic tissues resume growth, developing towards a seedling. Seed germination depends on both external conditions; the most important external factors include right temperature, oxygen or air and sometimes light or darkness. Various plants require different variables for successful seed germination; this depends on the individual seed variety and is linked to the ecological conditions of a plant's natural habitat. For some seeds, their future germination response is affected by environmental conditions during seed formation. Water is required for germination. Mature seeds are extremely dry and need to take in significant amounts of water, relative to the dry weight of the seed, before cellular metabolism and growth can resume. Most seeds need enough water to moisten the seeds but not enough to soak them; the uptake of water by seeds is called imbibition, which leads to the swelling and the breaking of the seed coat. When seeds are formed, most plants store a food reserve with the seed, such as starch, proteins, or oils.
This food reserve provides nourishment to the growing embryo. When the seed imbibes water, hydrolytic enzymes are activated which break down these stored food resources into metabolically useful chemicals. After the seedling emerges from the seed coat and starts growing roots and leaves, the seedling's food reserves are exhausted. Oxygen is required by the germinating seed for metabolism. Oxygen is used in aerobic respiration, the main source of the seedling's energy until it grows leaves. Oxygen is an atmospheric gas, found in soil pore spaces; some seeds have impermeable seed coats that prevent oxygen from entering the seed, causing a type of physical dormancy, broken when the seed coat is worn away enough to allow gas exchange and water uptake from the environment. Temperature affects cellular growth rates. Seeds from different species and seeds from the same plant germinate over a wide range of temperatures. Seeds have a temperature range within which they will germinate, they will not do so above or below this range.
Many seeds germinate at temperatures above 60-75 F, while others germinate just above freezing and others germinate only in response to alternations in temperature between warm and cool. Some seeds germinate when the soil is cool 28-40 F, some when the soil is warm 76-90 F; some seeds require exposure to cold temperatures to break dormancy. Some seeds in a dormant state will not germinate if conditions are favorable. Seeds that are dependent on temperature to end dormancy have a type of physiological dormancy. For example, seeds requiring the cold of winter are inhibited from germinating until they take in water in the fall and experience cooler temperatures. Cold stratification is a process that induces the dormancy breaking prior to light emission that promotes germination. Four degrees Celsius is cool enough to end dormancy for most cool dormant seeds, but some groups within the family Ranunculaceae and others, need conditions cooler than -5 C; some seeds will only germinate after hot temperatures during a forest fire which cracks their seed coats.
Most common annual vegetables have optimal germination temperatures between 75-90 F, though many species can germinate at lower temperatures, as low as 40 F, thus allowing them to be grown from seeds in cooler climates. Suboptimal temperatures lead to longer germination periods. Light or darkness can be an environmental trigger for germination and is a type of physiological dormancy. Most seeds are not affected by light or darkness, but many seeds, including species found in forest settings, will not germinate until an opening in the canopy allows sufficient light for growth of the seedling. Scarification mimics natural processes that weaken the seed coat before ger
Aquaponics refers to any system that combines conventional aquaculture with hydroponics in a symbiotic environment. In normal aquaculture, excretions from the animals being raised can accumulate in the water, increasing toxicity. In an aquaponic system, water from an aquaculture system is fed to a hydroponic system where the by-products are broken down by nitrifying bacteria into nitrites and subsequently into nitrates that are utilized by the plants as nutrients; the water is recirculated back to the aquaculture system. As existing hydroponic and aquaculture farming techniques form the basis for all aquaponic systems, the size and types of foods grown in an aquaponic system can vary as much as any system found in either distinct farming discipline. Aquaponics has ancient roots, although there is some debate on its first occurrence: Aztec cultivated agricultural islands known as chinampas in a system considered by some to be the first form of aquaponics for agricultural use, where plants were raised on stationary islands in lake shallows and waste materials dredged from the Chinampa canals and surrounding cities were used to manually irrigate the plants.
South China and the whole of Southeast Asia, where rice was cultivated and farmed in paddy fields in combination with fish, are cited as examples of early aquaponics systems, although the technology had been brought by Chinese settlers who had migrated from Yunnan around 5 AD. These polycultural farming systems existed in many Far Eastern countries and raised fish such as the oriental loach, swamp eel, common carp and crucian carp as well as pond snails in the paddies; the 13th century Chinese agricultural manual Wang Zhen's Book on Farming described floating wooden rafts which were piled with mud and dirt and which were used for growing rice, wild rice, fodder. Such floating planters were employed in regions constituting the modern provinces of Jiangsu and Fujian; these floating planters are known as either jiatian or fengtian, which translates to "framed paddy" and "brassica paddy", respectively. The agricultural work references earlier Chinese texts, which indicated that floating raft rice cultivation was being used as early as the Tang Dynasty and Northern Song Dynasty periods of Chinese history.
Floating aquaponics systems on polycultural fish ponds have been installed in China in more recent years on a large scale. They are used to grow rice and canna lily and other crops, with some installations exceeding 2.5 acres. The development of modern aquaponics is attributed to the various works of the New Alchemy Institute and the works of Dr. Mark McMurtry et al. at the North Carolina State University. Inspired by the successes of the New Alchemy Institute and the reciprocating aquaponics techniques developed by Dr. Mark McMurtry et al. Other institutes soon followed suit. Starting in 1979, Dr. James Rakocy and his colleagues at the University of the Virgin Islands researched and developed the use of deep water culture hydroponic grow beds in a large-scale aquaponics system; the first aquaponics research in Canada was a small system added onto existing aquaculture research at a research station in Lethbridge, Alberta. Canada saw a rise in aquaponics setups throughout the'90s, predominantly as commercial installations raising high-value crops such as trout and lettuce.
A setup based on the deep water system developed at the University of Virgin Islands was built in a greenhouse at Brooks, Alberta where Dr. Nick Savidov and colleagues researched aquaponics from a background of plant science; the team made findings on rapid root growth in aquaponics systems and on closing the solid-waste loop, found that owing to certain advantages in the system over traditional aquaculture, the system can run well at a low pH level, favoured by plants but not fish. Aquaponics consists of two main parts, with the aquaculture part for raising aquatic animals and the hydroponics part for growing plants. Aquatic effluents, resulting from uneaten feed or raising animals like fish, accumulate in water due to the closed-system recirculation of most aquaculture systems; the effluent-rich water becomes toxic to the aquatic animal in high concentrations but this contains nutrients essential for plant growth. Although consisting of these two parts, aquaponics systems are grouped into several components or subsystems responsible for the effective removal of solid wastes, for adding bases to neutralize acids, or for maintaining water oxygenation.
Typical components include: Rearing tank: the tanks for feeding the fish. Depending on the sophistication and cost of the aquaponics system, the units for solids removal, and/or the hydroponics subsystem may be combined into one unit or subsystem, which prevents the water from flowing directly from the aquaculture part of the system to the hydroponics part. By utilizing gravel or sand as plant supporting medium, solids are captured and the medium has enough surface area for fixed-film nitrification; the ability to combine biofiltration and hydroponics allows for aquaponic system to in many cases eliminate the need for an