Hydroponics is defined as growing plants, using mineral nutrient solutions, without soil.
Although hydroponic systems do not involve soil, they may involve a wide variety of growing media, such as perlite, gravel, peat, sand, rockwool and others.
Typical hydroponic crops include lettuce, strawberries, herbs, tomato, cucumber and flowers.
In hydroponic systems which do not involve any growing medium, roots are immersed in an aerated nutrient solution.
In hydroponics, most of the plant nutrients are supplied by the nutrient solution, rather than by the media in which the plants are grown.
Unlike soil, that stores nutrients, the growing media used in hydroponic systems have a little effect, if any, on the nutrition of plants. As a result, the only source of nutrients is the nutrient solution, and therefore you have total control over your plant nutrition.
While soil allows more tolerance for inaccuracy, hydroponics leaves very little room for errors. Because changes are rapid and mistakes can be very costly, hydroponics growers should make highly educated and accurate decisions.
There are two main types of hydroponic systems - closed hydroponic systems and open hydroponic systems. Hydroponic systems that do not involve growing media are usually closed systems, while hydroponic systems that involve growing media (container plants), may be closed or open systems.
In this type of systems systems the same nutrient solution is recirculated and the nutrient concentrations are monitored and adjusted accordingly.
Keeping the nutrient balance in such hydroponic systems is a challenge and the hydroponic nutrient solution has to be sampled and analyzed at least once a week. The nutrient solution composition has to be adjusted according to the results. If not managed properly, the nutrient solution might get out of balance.
Closed hydroponic systems include both simple hydroponic systems, as well as sophisticated ones. Here is a short brief of some of these methods:
Deep Water Culture (DWC) hydroponic systems - This is the most simple type hydroponic systems. In this type of systems, plants are suspended in an oxygen-enriched nutrient solution.
The Wick hydroponic systems - This is a passive system, in which wicks run from the base of the plant container down to a reservoir and draw the nutrient solution upwards.
Ebb and Flow - This is the most popular hydroponic system due to its low maintenance and low cost. It is widely used for plug production and potted plants. In this type of system the growing bed is flooded with nutrient solution and then it is allowed to drain. The duration and frequency of the flood depends on factors such as the type of growing medium used, size of containers and plants water requirements.
NFT (Nutrient Film Technique) hydroponic systems - This system uses a continuous nutrient solution flow over the roots. This results in a thin film of nutrient solution around the roots, allowing them both aeration and access to nutrients.
In open hydroponic systems a fresh nutrient solution is introduced for each irrigation cycle. The nutrient solution is usually delivered to the plants using a drip system. An adequate run-off must be maintained in order to keep nutrient balance in the root zone.
An open hydroponic system