Hydroponics - Generalities

1.1 Definition
1.2 Growth considerations
1.3 Hydroponic methods
1.4 Hydroponics medium

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 Hydroponics System
 

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1.1 Definition
As wiki says, "Hydroponics is a subset of hydroculture and is a method of growing plants using mineral nutrient solutions, in water, without soil. Terrestrial plants may be grown with their roots in the mineral nutrient solution only or in an inert medium, such as perlite, gravel, mineral wool, expanded clay or coconut husk". The soil itself is not essential to plant growth.
In other words, main advantages of hydroponics are:
a) no soil required for growth - plant roots must reach water, air and nutrients;
b) water and nutrients recirculation - saves water and nutrients (which is optional);

1.2 Growth considerations
Some aspects when starting a plant growth should be known:
1.2.1 Growth stages:
a) propagation - refers to planting seeds (sowing), cloning plants; it is the period till the plants forms roots, until they are ready to grow on their own; propagation requires a special medium and it is done separated from the growth medium; seeds and clones are usually kept in a mineral wool medium, they require a non aerated, warm medium and humidity to force growing of roots; seedlings and clones should be only moist with water and nutrients and not excessively watered; the propagation period takes about 1 week (7 days); some seeds (if specified) require a dark medium.
b) grow - this is the period till the propagation and until the blooming period (where the plants starts flowering) - it is determined by the period when plants develop leaves; for the grow period, the plants should be moved from the initial propagation medium to their final destination that will ensure both grow and blooming stages; water, illumination, ventilation and nutrients is important, as in this period plants develops leaves and they are suitable for most growing; the grow period depends on the plants we seed; some plants require more weeks in this period.
c) bloom - the period when the plants start flowering; it is only valid for the plants that develop flowers; the medium conditions are the same as for the grow period, with the exception that the blooming period requires some extra special nutrients to ensure and boost the blooming; the blooming period depends on the plants we seed; some plants require more weeks in this period; this is the final stage for decorative and ornamental plants.
d) harvesting - this is valid for the vegetative plants (the ones that develop usually only leaves) and not for decorative and ornamental plants (the ones that develop flowers) - this is the final stage for our growth.
1.2.2 Illumination, aeration, ventilation, humidity, nutrients and parasites:
a) illumination - in propagation stage, illumination is required 12 hours per day (that if not specified that seeds must grow in a dark medium; at grow and blooming stages, illumination is required 16 hours per day;
b) aeration - is required in grow and blooming stages - the roots should be aerated;
c) ventilation - is required in grow and blooming stages - the leaves and flowers should be ventilated;
d) humidity - is important in all the stages - it is usually obtained by water vapors under a warm medium;
e) nutrients - are not especially required for seeds in the propagation stage, but is important for all stages after the plant develop roots; as the nutrients are mixed with water, the final solution should be carefully observed by measuring the pH; pH measuring is done with the help of pH testers, the limits should be between 5.7 and 6.2 and the regulation is done with the help of pH down (alkaline solution) and pH up (acid solution); usually, a general formula for the nutrients is NPK=795 percents, where N=nitrate, P=phosphorous, K=potasium); beside NPK, the nutrient formula may contain: copper, manganese, bohr, zinc, aso.
f) parasites - this also refer to infections - as much as possible, the hydroponic system should be protected of plant parasites and infections; the plant roots should not be exposed to illumination (as illumination ensures the growth of water algae); however, there exist special solutions to protect plants.

1.3 Hydroponic methods
There are several methods for hydroponics implementation, the main are presented below:
1.3.1 Static or passive irrigation - plant roots are kept directly in a water medium; the main disadvantage is that roots are not oxygenated, so, a complementary aeration solution is required;
1.3.2 DIY ("do it yourself") - the system is mounted into the light, usually beside windows and consists in continuous tanks recirculation - the upper tank waters the bottom tank, aso;

 Variant of DYI System

1.3.2 Continuous flow, also known as NFT (nutrient film technique) - water and nutrients is recirculated via tubes, in which plant roots reside; the advantage is water and nutrients recirculation, also the roots are aerated because of the upper part of tubes that are not watered;

 NFT System

1.3.3 Ebb, flow and drain - the plants resides on a tray above a water and nutrients reservoir or tank; at regular times, the tray (and subsequently the plants) is filled with water and nutrients which is then drained back in the tank;

 EBB & Flo System
 

1.3.4 Dripping - this is kind of EBB, flow and drain with the difference that water and nutrients are passed to roots via thin capillary tubes, the roots are watered and the water excess is drained back in the tank;

Dripping Aystem

Of course, there are other hydroponic methods and also alternatives to hydroponics: aeroponics and aquaponics.
Note: the system presented at "3. Building the hydroponic system" is kind of a dripping hydroponics method.

1.4 Hydroponics medium
The medium on which plant will grow consists of an alternative to soil medium:
1.4.1 coco, or coir - used in grow and blooming stages, coco is a natural growing medium; coco is obtained from the outmost fibers of coconuts; it is probably the best hydroponic growth medium;
1.4.2 clay balls - also called hydroton - is an alternative to soil; the clay is cooked at high temperature which causes clay to expand and become porous, forming balls; the balls will be inert, pH neutral and will not contain any nutrient value; it is used in grow and blooming stages;
1.4.3 rock wool - is a mineral wool, an artificial alternative to coir; it consists of fiber glass that maintains water and nutrients; it is used especially in propagation stage, but it may be used also in the grow and blooming stages; the disadvantage is that glass fiber may be harmful to roots;
1.4.4 perlite, pumice, vermiculite - volcanic rock, used as alternative to clay balls;

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