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The hydroponie or hydroponic Culture (or agriculture out-ground ), of Latin ponos: effort and hydro: water, is the culture of Plante S carried out on neutral and inert substrate (of type Sable, Pouzzolane, balls of Argile, etc). This substrate is regularly irrigated of a current of solution which brings rock salt and nutrients essential with the plant. This process has many advantages: less consumption of Water, controlled and fast growth, less attack of vermin of the ground, better control of precocity.

The hydroponic culture also allows an automation of the culture: temperature, lighting, control of pH and the concentration in nutritive elements of the liquid, ventilation.

The hydroponic culture is very present in horticulture and in the culture forced of some Légume S under greenhouse. This farming technique developed to lead today to the aéroponie and since very recently the ultraponie. It makes it possible to accelerate the process of maturation of the fruits thanks to a nychthemeral Rythme faster and allows several harvests per annum.

Introduction

So that the plants push in an optimal way, they require for light (that it is natural or artificial), of a stable and moderate temperature, a sufficient Hygroscopy of the air thus that of a satisfactory oxygenation of the roots, finally, of an adequate food in made up sufficiency of water, rock salt and of Trace element S.

The plants have a Métabolisme which is able to assimilate food and to eliminate them in the form of waste, like good number of beings of the reign of the alive one. Motionless living beings, the plants assimilate their food in the form of water mineralized thanks to their roots, and energy necessary to metabolize by the light. In nature, it is the ground which plays the part of nutritive salt tank. It is however very rare to have a ground of quality which has all the elements necessary to the life plants in optimal proportions; moreover, the adequate Acidité is specific to each plant, each plant, and can largely vary according to the ground, of the weather or of the seasons. The pot cultures and the cultures of flowers, for example, require a pH ranging between 5.5 and 6.5 (acid). The ground has Humus containing agents chelates, also called substances plugs, substances which have the capacity to keep the acidity of the ground to balance by absorbing substances which are there in surplus, to possibly release them when the conditions vary. In the case of the cultures out-ground, the cultures proceed without ground, being thus released from the constraints dependant on the traditional land cultures.

From here a quarter century, the world population will increase by 3 billion inhabitants, of which 95% will make left the Pays in the process of development, which will pose a problem of resources if one does not find the means of doubling the production of food of our planet. The actual position of our environment and the state of pollution of our grounds do not allow any more to consider an increase in the agricultural production in the long term. The economy of water is with the day order.

The culture out-ground is an alternative novel method of culture of the plants which can be installation, in horticultural exploitations of all sizes, or for the development assistance of the poorest urban populations. Being able to constitute an answer to the problems of water and pollution which our planet knows, being with the service of the researchers who use this technology to make research on the plants, that it is for the medicinal plants or for the Micro-organisme S embarked in the spaceships…

History

First appearance of culture out-ground

This technique exists since mists of time, one of the examples among most famous and oldest are the Jardins suspended of Babylon, but there existed also people which lived at the edge of lakes of high mountains of the Peru like the Titicaca, where they cultivated their kitchen gardens on the surface of water. The Aztèques as for them were established in the marshes close to the future town of Mexico City and concevirent kind of made rafts of snap rings and reeds covered with a layer of silt on which the farmers gardened, and who it is always possible to see nowadays. The roots of the plants plunged in the water of the lakes: without the knowledge, they were the precursors of a species of primitive aquiculture.

The Chinese still employ thousand-year-old techniques of culture on gravel.

The culture out-ground which one knows nowadays was born at the XIXe century in Germany. It was discovered within the framework of research carried out in order to discover what nourished the plants. It is only into 1930 that Gericke produced the first commercial hydroponic system with the the United States. During the Second world war, American cultivated hydroponic vegetables in volcanic islands of the Pacific to ensure the contribution in vitamin necessary to the good health of theirs troops which were there in garrison.

Since, tests proved the viability of the technique, like its economic potential and environmental.

Today, the culture out-ground is practiced in agriculture on million hectares in world. A great number of fresh vegetables like the Tomato, the Cucumber, the Zucchini, the Lettuce, the Sweet pepper, the Pepper S, the spinach S, the Broccoli S, the Bean S, the Carrot S, the Beet S, the potatoes, the aromatic herbs, which are cultivated in greenhouse result from cultures out-ground, and, it is also the case of the majority of the cut flowers which one finds in the florists.

The first research on manures

It is the Baron Justus von Liebig (1803-1873), chemistry teacher at the university of Giessen, which was one of the pioneers of research in the field of physiological chemistry. He was the founder of agricultural Chemistry and formed a certain number of the largest chemists of its time. By observing a plant quite simply that it had made burn, it concludes that the elements present in ashes, Azote, Phosphore and Potasse, nourished the plants, and that those transformed mineral matters coming from the ground and of the atmosphere into Organic matter. Thanks to this discovery, it makes a success of its first experiments with artificial manures. Before Liebig, the virgin grounds were very fertile and full with humus. One thought that this brown matter, pourrissante, were, at his various stages, the primary source of food of the plants. Liebig tackled this concept with force.

In 1905, Fritz Haber, a German chemist, discovered a process making it possible to transform nitrogen of the air into Ammoniaque liquid, consisted of nitrogen 80%. In 1915, it joined Karl Bosh, a German engineer, to draw up the plans of the first synthetic ammonia factory of Reich, with dramatic historical consequences.

Each war, at the beginning of the 20th century was the ground of chemical tests to large scales. With end of the second world war, the principal ammonia mines had to find other outlets, thus firms like Dupont, Dow, Monsanto, American Cyanamid with the enormous ones profits carried out during the war, produced even more manure.

The first research on the cultures out-ground

The beginnings of the culture out-ground go back to the XVIIe century. At this period, one still thought that them plants were formed starting from water. At the beginning of the XVIIIe century, John Woodward thought that it was the ground and not the water which created the plant, this following its experiments of culture without ground.

It is only in 1758 that Duhamel of the Heap had the idea to resume the studies of the culture without ground. It made germinate of seeds in sponges, to then plunge the roots of the plants in a solution of manure. He deduced from his experiments which the plant did not absorb only water, but also the minerals which were dissouts there.

All these new discoveries brought to make new research. The first research on the culture out-ground known as modern, will be carried out following the discoveries on the mineral nutrition of the plants, carried out by Justus von Liebig. These first outlines will be called hydroponic, or hydroculture, word which comes from the German word Hydrokultuur. This culture replaces from now on the traditional ground by a regularly renewed nutritive solution, and allows the culture of a great number of vegetables as well as certain fruits.

Following these discoveries, the scientists really started to be interested on this subject. However, to be exact, the discovery of this technique must be allotted to two German researchers Knop and Sachs, which, while working on the fertilization of the plants, highlighted the role of water, the air, and the ground. And it is precisely by seeking the role of each constituent element the ground, that they realized that this one could be completely reconstituted in an artificial way. At the same time and in manners independent, they succeeded in making push plants on entirely liquid mediums made up of water and rock salt.

The cultures out-ground developed quickly, because the outputs obtained were higher with the outputs of the traditional cultures, and the costs were seen some strongly decreased.

Various substrates

One chemically understands by inert Substrat… substance (which is unable to react with other substances), which replaces the ground, and which is used as support of culture for the plants. It must protect the roots of the light and enable them to breathe. But the substrate conveys also the nutritive solution to the roots of the plants.

There exist several substrates, like several alternatives of use:

the substrate can be placed in bulk in vats.
the substrate is in envelopes which are laid out horizontally (often filled of coconut).
the substrate in the form of breads is surrounded by opaque plastic film, and is laid out horizontally, either on tables, or on the ground (they are rockwool breads).
the substrate is suspended in bags vertically under the greenhouses (often filled of pearlite).

the Pearlite

This material with the aspect of granulated of bed linen for cat, white color. It is a siliceous sand of volcanic origin containing of the water which is expanded industrially by a treatment heat (1200°C). It is composed of Silice, of Alumine, Oxide iron, oxide of Titane, Chaux, Magnésie, oxide of sodium and Potasse. It has a very great water holding capacity (4 to 5 times its weight) its pH is from 7 to 7,2, and it is used for the culture on substrate, pure or mixed.

The Vermiculite

This material with the aspect of pellets. It is an aluminosilicate (Mica) which is expanded by a treatment heat. It is composed of Magnésie and Alumine. It is very light and has a great water holding capacity (approximately 350 L with the m ³), while ensuring a good drainage. Its pH is from 7 to 7,2.

It is often used in vats or pots, for the realization of sowing, or during the rooting of Cutting S.

advantages:

It is very light
It has a very good water holding capacity
It is chemically inert
It is insulating

disadvantages:

Its price is very high
It is degraded easily in dust and packs
It flies away easily because it is very light
It is difficult to disinfect

Clay balls

This material resembles small brown balls which one uses to cover the pots with flower, the pellets are obtained by a treatment of strong heat of the Argile. Clay expanded has a good capacity insulating, which is necessary to protect the roots of the changes from temperature.

It is composed of Silice, of Alumine, and iron oxides, Soufre. Its water holding capacity is of 15% in mass. It is used for the culture out of container, on systems of tables with tides, or one more small scales in hydroponic systems with continuous flow. Contrary to them, rockwool clay balls are a substrate durable, healthy, biological and ecological.

Rockwool

This material is in the form of breads or of flakes, resembling the insulator which one uses to isolate the roofs from the houses. The rockwool is industrially manufactured starting from volcanic rocks molten and extruded with more 1500°C, it is then made absorbent by the addition of a special oil. It is made up of silica, alumina, lime, titanium oxide, magnesia, oxide of manganese, potash, iron oxide, and sodium oxide. The rockwool is not chemically inert, it can release from the Calcium.

Coconut fibers

This material is in the form of breads or in form rough to place in vats, or pots. The coconut fiber is manufactured starting from the bark of Coconut grated, then treated. It is of neutral pH, it is an inert substrate.

Advantages:

It is reusable on the condition of being disinfected between each use
It is very ventilated
It is rather cheap
It is stripped of parasite at the beginning
It has a weak thermal inertia
It is biodegradable
It has a very good water holding capacity

Inconvénients:

It has a low water holding capacity
It is heavy
it loses its porosity during its use

Novel methods

The NFT

Conceived by the Cooper English in 1979, it is one of the techniques without substrate most used in horticulture. As it is very difficult to air a stagnant liquid, the nutritive medium circulates on a low thickness (a fine water film) under the roots, which brings a strong oxygenation of the nutritive liquid, from where the name of “Technical Nutriment Film”.

The nutritive solution which is sent in the drains by a pump located in a tank enriches out of oxygen on the level by surface by liquid film thanks to its continuous displacement. Watering is carried out by streaming under the roots of the plants, which are laid out in a kind of tube or slightly inclined gutter, so that the liquid turns over in the tank after having been in contact with the roots.

This system functions in closed circuit, which means a limited evaporation, and thus a great water saving. The solution must however be readjusted permanently as well in volume as in concentration in biogenic salts, the solution being absorbed by the plants. This method presents a disadvantage: the plants which are located in end of the circuit receive a food impoverished of oxygen, and sometimes of nutritive elements.

One especially finds this farming system in France and Brittany for the tomato culture, in Belgium, rather for the lettuce culture.

Advantages:

This system brings a good oxygenation.
It allows a homogeneous watering.
It is economic because it uses only one fine water film.
It makes it possible to obtain a high output
As it does not use any substrate, it does not pose any problem for the bearing of the cultures.

Inconvénients

the plants which are located at the end of the cycle can receive a food impoverished of oxygen and nutritive elements.
This system is not very ecological because it generates the payment of the solution in the environment.
As it functions in closed circuit, it increases the chances of propagation of the diseases.

The Aéroponie

The aéroponie represents one of the most recent developments in the farming techniques out-ground and also one of the most sophisticated. Indeed, the roots of the plants are in contact neither with a solid medium, nor even with a liquid medium: they are fed by a nutritive fog obtained by Brumisation of the nutritive solution in closed circle.

The aéroponie is a system which optimizes the growth of the plants by creating ideal balance between the circulation of the nutritive solution and the quantity of oxygen which is dissolved there. The solution is recovered then re-used: the system functions in closed circuit, which limits the evaporation of water. Atmosphere culture medium where the roots are is saturated by a nutritive fog which settles on the roots then streams on these last by ensuring their mineral food.

This system ensures an excellent output, which is due to the fact that the plants which push in aéroponie create a mass of roots much more important than the others. The pulverization, which can be continuous, is in general discontinuous, by cycles from 15 to 20 minutes, with stops of a few minutes during the day, and of a few hours during the night.

Advantages:

Increase in the number of crop plants per m ²
Reduction of the treatments against the parasites, the medium being sterile.
As this system functions in closed cycle, it avoids the contamination of the ground water and the environment
Économie of water from approximately 90% compared to a traditional ground culture.
As it does not require a substrate, it does not have there problems of waste.
it is possible to cultivate all the species of plants with this system.

Disadvantages

As this system functions in closed cycle, the extension risk of diseases is increased.
being stripped of substrate, this system is very sensitive to the temperature variations.
This system generates maintenance, the systems of brumisation stopping itself easily.
It is expensive with the purchase because the system of watering requires the contribution of a pump as well as filter.

The Ultraponie or airponie

This technique is the most recent technology left the laboratories of researchers.

It is a new improved system aeroponic, based on a fine fog produced by a brumisator with Ultrason S. The brumisator with ultrasounds is an electrical appliance having of the membranes of Céramique which vibrate at a certain frequency (1,65 MHz) that is to say more than one million six hundred and thousand vibrations at the second; when water passes above, it is literally transformed into made fog of extremely fine droplets (less than 5 microns). The apparatus which is placed in the tank is on a kind of buoy which maintains it between 3 and 4 cm of surface. The roots of the plants push in opaque vats resembling enormous tubes.

The roots are fed by the lower part by the fog made of these very fine droplets thus forming a medium made up of water and directly assimilable oxygen by the pores of the roots. In the most recent systems, rock salt are provided by traditional brumisateurs to protect the apparatuses with ultrasound from corrosion. The fog is in continuous motion in the tubes thanks to a kind of small ventilator incorporated on the brumisator in ultrasound, which makes circulate the fog and enormously accelerates the process of absorption of the roots.

As is completely completed, that limits the evaporation of water and the consumption out of water is very low. This system successfully allows germination as well as the rooting of the cuttings, but also the culture of the majority of the plants and mushrooms. The crop plants with this system will see their strongly accelerated growth, and their production will be maximized.

This system is used successfully in space research, for the rooting of the Chrysanthème, to make bean cuttings, for the production of chrysanthemums, of lettuces, for the growth and the flowering of tomatos, for the germination and the growth of beans and the radish growths. Moreover, it is recently adapted for the conditioning of the fruit and vegetables all along the chain of distribution until the custom. The weight of the plants and their system racinaire is twice larger than in the ground. In certain big cities, it is used for the brumisation of public places.

Advantages:

This system increases the productivity of the plants.
This system is simple of use because it is entirely controlled.
This system exempts the installation of the pumps and the usual filters.
It does not consume much water because it is a closed cycle, and does not consume much electricity.
It makes it possible to realize savings of manure
This system limits all chances of infestation of insects or diseases.
This system improves vitality of the plants.

Disadvantages:

This system generates a large investment according to the size of the installation.
It is prone to the temperature variations, and can cause damage with the roots if those are too high or too low.
It requires knowledge in data processing for the professional installations.

The hydroponie

The hydroponie is a term which gathers the various farming techniques out-ground, but it is also a rather simple farming system, which does not require much material and which does not generate large expenses. The hydroponie is the first culture of plants out-ground which was developed with industrial scale. The word comes from the Greek “hydro=eau” and “ponos=travail”

This technique consists in nourishing the roots of the plants which are in substrate (for example, in rockwool breads) with a nutritive solution, this principle makes it possible the plant to have a better access to oxygen, water, like food. The control of the pH of the solution like its electroconductivity makes it possible to manage the medium compared to the needs for each plant, and with each stages of their life. Thanks to this principle, the plant is pushed to the maximum of its genetic potential and it will produce larger flowers, larger fruits and, in the case of the medicinal plants, those will see a strong increase in the production of their concentration in theory active.

This system makes it possible to be used as support the plant throughout the cycle of its life. The simplicity of the system allows a rather simple and fast maintenance.

Advantages:

This system allows an increase in the production the m ²
It makes it possible to make an energy and water saving.
Shortening of the period of culture (of at least a week on a cycle compared to a traditional culture on ground).

Disadvantages:

This system is not ecological, because, after having sprinkled the substrates, the nutritive solution is not reusable.
It causes an increase in moisture in the culture medium.
the use of substrates causes an important accumulation of waste.

System with tide

This technique consists in making push plants on substrate placed in containers tight of plastic called tables with tide. They are called thus because they resemble large tables having an edge a height which can vary from ten with a score of cm. There exist several possibilities of cultures with this system: either one can place clay balls, or envelopes or various substrates directly in the table, or pots for the rooting of the plants in horticulture.

Most usually used are the coconut, the balls of clays or the rockwool breads. The substrates are fed in nutritive solution by their lower part during a rather short amount of time but frequently water remains a certain time there according to the substrate, then gravity makes it evacuate in the tank. In general, water arrives by the backhander, thanks to a pump which is placed in a tank located under this one. To prevent that water stagnates after the watering, a system of drainage is placed on the bottom of the table so that water runs out by a pipe which turns over in the tank after recovery, the cycle starts again. What allows the roots of réoxygéner after each cycle of watering.

Thanks to this system, the roots easily have access to food like with oxygen.

This system allows a density of plantation higher than the other systems. Moreover, it is enough simple to regulate the pH as well as EC. of the solution. Thanks to this system, all the plants will be sprinkled in even time and with the same quantity of nutritive solution, which decreases the differences in sizes of the plants and guarantees a homogeneity of harvests. This system allows a great time-saver and of money. This system with recycled solution is especially used for the cultures of house plants under greenhouse.

Advantages:

Rather simple to set up
does not generate large expenses
Offre a homogeneous food of the plants
easy Maintenance and rapid
Recyclage of the nutritive solution

Inconvénients:

the recycling of the nutritive solution can strongly make vary the pH and EC.
the closed circuit increases the extension risks of the diseases.
is not adapted to all the types of cultures
Grande loss of water per evaporation

System drop by drop

This farming system is a system on substrate which requires goutteurs or capillaries, as well as a pipe of distribution and a pump. In culture out-ground on substrate, one uses at least a gouttor by plant. But for more reliability one uses two per plant of them. The nutritive solution is distributed to the plants by discontinuous irrigation on the upper surface of the envelope or of the pot then streams by gravity towards the lower part of the substrate. The pots and the envelopes are bored in the content to make it possible water to run out.

In general this system does not recycle the solution which is not re-used. Thanks to this system, one can sprinkle the plants directly with the roots. This system is one of most widespread currently.

This technique is not very ecological, being given the possible contamination of the ground by nutritive waste of solution, and is not very economic considering the great quantity of water used to make the culture.

System with continuous flow

This system generally of small size and consists of several small units. This system with multiple applications. It is especially used for the culture of plants mothers (Plant on which one takes cuttings), for culinary or aromatic plants.

This technique makes it possible the plants to fully open out. The plants push in opaque vats generally filled with clay balls, because this substrate does not generate waste and thus does not clog the tank which is placed at the lower part. To prevent that the roots are not damaged by the pump, here, it is another technique which is used. An air pump sends the solution in a column of pumping, then distributes it by a ring of distribution. Water streams through the clay balls then falls down in the tank (system of the type Aquafarm or Waterfarm). The continuous motion of the flow of the solution made gorge itself with oxygen and humidifies the roots constantly; those draw food there more easily.

Advantages:

Simple of installation
Autonomie of the system
Decreases evaporation because watering is done directly with the roots
This system generates very large harvests with small scales
It makes it possible to very quickly obtain very large plants and of the guards in full form very a long time.
It requires a system of relay the binder to a large tank.

Disadvantages:

possible Contamination of the grounds
Difference between the flow of the capillaries
regular Maintenance
important: Replacement of the material
It requires the purchase of pumps with surface.
It does not make it possible to make large harmonious cultures
It generates a strong increase in moisture
It is not economic out of water because this system extremely undergoes the evaporation of its solution.

Farming systems without substrate

The Aquiculture

Or deep water culture. It is historically the oldest method which corresponds to the use of the first nutritive solutions, developed about 1860 by Knop and Sachs.

The roots are plunged in a liquid medium, the nutritive solution being contained in a vat of variable culture of size (in general of opaque plastic). The vat must be painted in white outside to avoid the heating of the liquid inside. As the nutritive solution is stagnant, the quantity of oxygen is weak and generally insufficient for the good performance of the roots. To avoid a partial asphyxiation (hypoxia), it is necessary to enrich the medium regularly oxygenates some by insufflating air to him (starting from a compressor, of a turbine or more simply of an air pump for aquarium) or by adding h2o2 (hydrogen peroxide). This ventilation can be continuous, but it is generally discontinuous, with regular interval during all the cycle. This bullage of air also supports the mixing of the solution which avoids the precipitation of manures like their concentration around the roots. (What can cause the drying of the roots and cause the death of the roots).

The quantity of water is variable according to the age of the plant, that can vary between 1.5 L with 15 L. to compensate the evapotranspiration and weak evaporation, this solution must be regularly supplemented with pure water, because with this system, the plant having its roots completely plunged in the solution, it absorbs more water than of rock salt, which can vary the pH and EC. It is nevertheless necessary to replace the solution by a news at least once a month.

This farming technique is by far that which will have a better output on the level of the quantity of production of fruits or vegetables, thanks to this technique one can manage to obtain enormous fruits, the roots being directly plunged in the solution, they have access to all food, this more than in sufficiency.

Aquiculture is very can used in industrial agriculture, it is more frequently used for research, because it makes it possible to calculate with a high degree of accuracy the exact quantities of water and salts minerals which the plants use to push.

However horticultural productions approach this farming technique: production salads (especially in China), forcing of endive, and in rarer cases culture of strawberry.

Advantages:

This system obtains very large output.
It is not very expensive with the installation.
It does not require much maintenance for its good performance.
As it does not use any substrate, it does not cause a problem to manage this waste.
It makes it possible to calculate with a high degree of accuracy the exact quantities of water and rock salt that the plants use to provide for their needs.

Disadvantages:

With this system the culture on large surface is not easily possible.
It requires a great quantity of water.
It requires the purchase of expensive material to regulate the various variations of pH and EC.
It is not very ecological because it generates a great quantity of nutritive solution rejected into the environment.
This system requires the contribution of tutor to maintain the plants.

Conclusion

Since its initial state, the culture out-ground knew a great evolution, and a great improvement of these techniques, thanks to all the researchers whom they impassioned. A multitude of alternatives of this technology were born, and of the applications theirs were found.

Today its potential is not any more to prove, provided that it is well controlled, it makes it possible to obtain fabulous results, while making great savings in water. Thanks to this technique one can make push a multitude of plants all while allowing them to provide 100% of their genetic potential.

This is why the culture out-ground is one of the solutions installation to solve the current problems and to come from the lack of water, malnutrition and agricultural under-production of our planet. But it is also the solution which the researchers consider for the space voyages from long life, and the future colonization of new planets like Mars or the Moon.

The adoption and the development of these types of cultures in industrial agriculture, in spite of their great potential, are limited because of the importance of the capital which it should be invested so that they are installations. Moreover, they generate more important expenditure electric, which still slows down many peasants to install them. In addition the quality-price ratio brings little by little an evolution of mentalities. The growing market demand east and to be able to answer at the request of the consumers which grows each day a little more, the development of this type of cultures is undoubtedly into strong increase.

See too

Chinampa, one of the first hydroponic techniques
Site Fleursdubien Site of current events and information on the hydroponie

Simple: Hydroponics

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