Hydroponics involve growing terrestrial plants using water and mineral nutrients, in the absence of soil. In hydroponics, growing mediums or substrates such as peat, perlite and gravel are used. There are five fundamental types of hydroponics systems, but there exist hundred of variations on these five types of systems. All hydroponic methods are either a combination or a variation of these five hydroponics systems:

Ebb and Flow System

The Ebb and Flow system is also called flood and drain system. It operates by momentarily inundating the grow tray with nutrient solution and draining the same solution into a reservoir. A pump submerged in the nutrient reservoir, which is joined to a timer, does this work. When the pump is turned on by the timer, nutrient solution is delivered to the grow tray until suitable flood levels are reached. When the pump is turned off by the timer, the nutrient solution in the grow tray flows back through the pump into the reservoir. The flooding cycles depends on the type of growing medium used, humidity, temperature, type and size of the plants. The timer is normally set with these factors in mind.

The flood and drain system is highly flexible in that it can be use with a wide range of growing mediums. Customary, there are two main ways you can grow plants using this system. One method is to fill the grow tray with growing medium such as gravel, clay pebbles or grow rocks and then plant your seedlings. Another way and the most preferred method is to plant your seeds or seedlings in individual pots filled with growing substrate and then place the pots in the flood tray. This method allows the gardener to move the plants easily.

The Ebb and Flow systems are famous for organic production using hydroponics since heavy nutrients are used. In addition, the parts used in this system are straightforward and easy to operate. For a beginner, this is an excellent choice to commence your hydroponic gardening.

The demerit of this system is that a variety of growing medium such as grow rocks or clay pellets do not hold water appropriately. This causes drying of the plant roots incase water supplies are cut short due to timer or pump failure.

Deep-Water Culture System

The deep-water culture system is the most popular of all hydroponic systems. It involves allowing the plant root system to develop down into the mineral nutrient solution. Floating Styrofoam is used to holds the plants or the plant cups in place. This system is preferred for growing water-loving plants such as leaf lettuce.

A simple deep-water culture requires a watertight container. The container is filled with hydroponic nutrient solution and covered with Styrofoam to support the plants or the plant cups. In addition, an air pump that delivers air to the air stone that stirs the nutrient solution are also included in the set up. This allows the plant roots to access fresh oxygen and keep the nutrient solution well mixed.

One of the major advantages of the deep-water culture system is that it is of simple design. It is also the least expensive hydroponic system to build and maintain. Furthermore, water culture systems do not suffer from clogging, like in aeroponic systems, thus preferred for growing plants using organic nutrients. These advantages make water culture system a superb choice for beginners. The downside of water culture method is that it does not favor long-term plants or large plants.

Drip Systems

Drip systems are widely applied in commercial growing establishments worldwide. In drip systems, the plant roots are not submerged in the nutrient solution like in deep-water culture systems. Drip systems have a submerged pump in a nutrient reservoir that is timer controlled. Basically, the timer turns the nutrient pump on supplying the grow tray with nutrient solution. The nutrient solution is delivered specifically onto the base of each plant via a small drip line. An air pump is used to supply fresh oxygen to the nutrient solution. Normally the grow tray is filled with a growing medium.

There are two varieties of drip systems: Recovery and Non-Recovery System. The recovery system allows the surplus nutrients solution to be collected in a reservoir mainly for recycle. In this case, low-priced timers are employed since a recovery system does not need control of the watering sequences. In a non-recovery system, the excess nutrient solution is allowed to go to waste. For this reason, precise timers are used to control watering cycles and ensure that the plants get optimum nutrient solution and wastage is minimized. This make non-recovery systems cheap to maintain as the pH and nutrient strength of the reservoir will not require regular adjustments. This is because the excess nutrient solution is not allowed to flow back to the reservoir. Once you have filled the nutrient reservoir, you can leave the system unattended for a long time until the need arises. On the other hand, recovery systems experience variations in nutrient level and pH, which call for periodic testing and correcting.

The major drawback for the drip system is that emitters experience clogging problems, which can lead to enormous losses if not well maintained. Because of clogging problems, drip system cannot be used for organic production. Furthermore, it impossible to control the nutrient solution flow rate on a drip system.

Nutrient Film Technique (N.F.T)

In this hydroponic system, the plants roots are in contact with a constant flow of oxygenated, nutrient solution. The nutrient solution enriched with oxygen is supplied to a grow tray by a submerged pump. The nutrient solution then flows over the root system and back to the reservoir. A timer is not required for the pump since there is a constant flow of nutrient solution through the grow tray. One end of the grow tray is raised a bit higher to allow free flow of the nutrient solution. The plants are grown at equidistance along the growing tray. The nutrient film is maintained at shallow levels in the grow tray to allow the root system to absorb oxygen from the immediate air. Depending on the width of the grow tray, a broad choice of plants can be grown via NTF.

One of the major advantage of NTF is that no growing medium is required hence reducing the cost of operation. The plants are anchored in place by plant cups, which allow the roots system to be in contact with the nutrient solution. This makes NTF hugely popular in commercial hydroponic gardening. It is also good for beginners since the design and operation of this system is straightforward. Another advantage of NTF method is that it produces higher yields and quality produces than other hydroponic systems. This is because the plants are exposed to fresh oxygen, nutrients and water through out their growth period.

On the downside, the root mass of the plants grown via this system can dry out real fast if the flow of nutrient solution is interfered with due to power failure or pump problems. In addition, only plant with roots sufficiently large to reach the nutrient solution can be grown using this system.

Aeroponics

In aeroponics, air is used as the growing medium, and the roots are allowed to dangle in a large, deep container. The roots are misted with nutrient solution after every several minutes. A short cycle timer is used to control the high-pressure pump for only some seconds after every few of minutes. The pump and the timer can be bought from dealers specializing in hydroponic products.

Aeroponic system is the most difficult hydroponic system to build and maintain. If the nutrient supply is interrupted, the root mass can dry rapidly due to direct exposure to air. The nutrient strength and pH changes rapidly due high rate of absorption. This requires regular checking and adjustments hence increasing the maintenance cost. Furthermore, the mist emitters can easily block if organic nutrients are used.

On the bright side, aeroponic systems can achieve exceptionally high plant growth rate and high yields if well maintained.