Introduction on Hydroponics :D

Hydroponics is a method of growing plants using mineral nutrient solutions, without soil.
Plants may be grown with their roots in the mineral nutrient solution.
Plants absorb essential mineral nutrients as inorganic ions in water.
In natural conditions, soil acts as a mineral nutrient reservoir but the soil itself is not essential to plant growth.
When the mineral nutrients in the soil dissolve in water, plant roots are able to absorb them.
When the required mineral nutrients are introduced into a plant's water supply artificially, soil is no longer required for the plant to thrive.

The two main types of hydroponics are solution culture and medium culture.

Solution Culture

Solution culture does not use a solid medium for the roots, just the nutrient solution.
The three main types of solution culture are static solution culture, continuous flow solution culture and aeroponics.
Static Solution Culture
In static solution culture, plants are grown in containers of nutrient solution.
There can be one to many plants per reservoir. Reservoir size can be increased as plant size increases.
A homemade system can be constructed from plastic food containers or glass canning jars with aeration provided by an aquarium pump,
aquarium airline tubing and aquarium valves. Clear containers are covered with aluminium foil, butcher paper,
black plastic or other material to exclude light, thus helping to eliminate the formation of algae.
The nutrient solution is either changed on a schedule or when the concentration drops below a certain level as determined with an electrical conductivity meter.
Whenever the solution is depleted below a certain level, either water or fresh nutrient solution is added.

Continuous Flow Solution Culture
In continuous flow solution culture the nutrient solution constantly flows past the roots.
It is much easier to automate than the static solution culture because sampling and adjustments to the temperature and nutrient concentrations can be made in a large storage tank that serves potentially thousands of plants.

Aeroponics
Aeroponics is a system where roots are continuously or discontinuously kept in an environment saturated with fine drops (a mist or aerosol) of nutrient solution.
The method requires no substrate and entails growing plants with their roots suspended in a deep air or growth chamber with the roots periodically wetted with a fine mist of atomized nutrients.
Excellent aeration is the main advantage of aeroponics.


Medium Culture
The medium culture method has a solid medium for the roots and is named for the type of medium, e.g. sand culture, gravel culture or rockwool culture.
There are two main variations for each medium, subirrigation and top irrigation.
For all techniques, most hydroponic reservoirs are now built of plastic but other materials have been used including concrete, glass, metal, vegetable solids and wood.
The containers should exclude light to prevent algae growth in the nutrient solution.

Subirrigation

Passive subirrigation Also known as passive hydroponics or semi-hydroponics, is a method where plants are grown in an inert porous medium that transports water
and fertilizer to the roots by capillary action from a separate reservoir as necessary, reducing labor and providing a constant supply of water to the roots.

Ebb and flow / Flood and drain subirrigation, a tray is placed above a reservoir of nutrient solution.
At regular intervals, a simple timer causes a pump to fill the upper tray with nutrient solution,
after which the solution drains back down into the reservoir. This keeps the plants regularly fed with nutrient solution.

Top Irrigation
In Top irrigation, nutrient solution is periodically applied to the medium surface.
This may be done manually once per day in large containers of some media, such as sand.
Usually, it is automated with a pump, timer and drip irrigation tubing to deliver nutrient solution as frequently as 5 to 10 minutes every hour.