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Researchers of plant metabolism have discovered that plants absorb nutrients as simple ions in water. In natural conditions, soil acts as a nutrient reservoir but the soil itself is not essential to plant growth. When the nutrients in the soil dissolve in water, plant roots are able to absorb them. When the required nutrients are introduced into a plant's water supply artificially, soil is no longer required for the plant to thrive. Almost any plant will grow with hydroponics, but some will do better than others. It is also very easy to do, you probably did it in kindergarten.
Hydroponics is useful to us in two main ways. First, it provides a more controlled environment for plant growth than soil thereby removing many unknowns from experiments. Second, many plant species produce more product in less time and sometimes of higher quality, which under certain economic and environmental conditions, makes hydroponics growing more profitable to the farmer. With hydroponics there are no soil-borne diseases, weeds to pull, or soil to till, and plants can be placed incredibly close to one another. This allows a large amount of food to be produced in very space-constrained places.
The first researcher of hydroponics was John Woodward of England, who, in 1699, grew plants in water to which he had added various soils. This demonstrated that the earth contained various substances which the plants needed besides water. In the mid- 19th century, the German plant physiologists Sachs and Knop grew plants in simple solutions of inorganic salts.
In 1929, Professor Gericke of the University of California, Davis demonstrated that plants could be grown soil-free all the way to maturity, growing tomato plants in water to a quite remarkable size. By analogy with the ancient Greek term for agriculture, geoponics, the science of cultivating the earth, Gericke coined the name hydroponics for the culture of plants in water (from the Greek hydros, water, and ponos, labour).
There are a variety of techniques employed in hydroponics. Some, while dispensing with soil, use relatively inert material as a physical support for the plant roots. Other techniques dispense altogether with any growing medium, delivering nutrient solution directly to the roots by a variety of methods.
The simplest method: the plant is planted in a container (pot or bag) of growing medium, and the container stands in a tray of nutrient solution. The medium generally has large air spaces, allowing ample oxygen to the roots, while capillary action delivers water and nutrients to the roots. A variety of materials can be used for the medium: vermiculite, perlite, clay granules, rockwool, gravel. Some newer media that are becoming popular are coirCoir (from Malayalam kayaru cord) is a coarse fibre extracted from husk, the fibrous outer shell of a coconut. Structure The individual fibre cells are narrow and hollow, with thick walls made of cellulose. They are pale when immature but later become har fibre, and cocoa bean shells. This needs the least maintenance of all hydroponic methods, requiring only topup and occasional replacement of the nutrient solution. This is commonly employed for large display plants in public buildings: in Europe a system using small clay granules is marketed for growing houseplants.
Example Image from HydroponicsOnline.com
In its simplest form, there is a tray above a reservoir of nutrient solution. The tray is either filled with growing medium (clay granules being the most common) and planted directly, or pots of medium stand in the tray. At regular intervals, a simple timer causes a pump to fill the upper tray with nutrient, after which the nutrient drains back down into the reservoir. This keeps the medium regularly flushed with nutrient and air.
Example Image from HydroponicsOnline.com
Similar to Flood and Drain in its physical setup, except the pump delivers a continuous trickle of nutrients, water, and oxygen onto the medium. The emitters are set to run 5 to 10 minutes every hour.
Example Image from HydroponicsOnline.com
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