Types of Hydroponics Systems.
The two main types of hydroponics are solution culture and medium culture. Solution culture does not use a solid medium for the roots, just the nutrient solution. The three main types of solution cultures are static solution culture, continuous-flow solution culture and aeroponics. 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 rock wool culture.
There are two main variations for each medium, sub-irrigation 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.
Hydroponic systems are characterized as active or passive. An active hydroponic system actively moves the nutrient solution, usually using a pump. Passive hydroponic systems rely on the capillary action of the growing medium or a wick. The nutrient solution is absorbed by the medium or the wick and passed along to the roots. Passive systems are usually too wet and do not supply enough oxygen to the root system for optimum growth rates.
Hydroponic systems can also be characterized as recovery or non-recovery. Recovery systems or recirculating systems reuse the nutrient solution. Non-recovery means just what it says. The nutrient solution is applied to the growing medium and not recovered.
Based on techniques used hydroponic systems can be divided in following 6 types: Wick, Water Culture, Ebb and Flow (Flood & Drain), Drip (recovery or non-recovery), N.F.T. (Nutrient Film Technique) and Aeroponic. There are hundreds of variations on these basic types of systems, but all hydroponic methods are a variation (or combination) of these six.
The Wick system is by far the simplest type of hydroponic system. This is a passive system, which means there are no moving parts. The nutrients are stored in the reservoir and moved into the root system by capillary action often using a candle or lantern wick. In simpler terms, the nutrient solution travels up the wick and into the root system of the plant.
This system can use a variety of growing medium. Perlite, Vermiculite, Pro-Mix and Coconut Fiber are among the most popular.
The wick system is easy and inexpensive to set-up and maintain. Although, it tends to keep the growing medium to wet, which doesn’t allow for the optimum amount of oxygen in the root system. The wick system is not the most effective way to garden hydroponically.
The biggest drawback of this system is that plants that are large or use large amounts of water may use up the nutrient solution faster than the wick(s) can supply it.
WATER CULTURE SYSTEM
The water culture system is the simplest of all active hydroponic systems. The platform that holds the plants is usually made of Styrofoam and floats directly on the nutrient solution. An air pump supplies air to the air stone that bubbles the nutrient solution and supplies oxygen to the roots of the plants.
Water culture is the system of choice for growing leaf lettuce, which are fast growing water loving plants, making them an ideal choice for this type of hydroponic system. Very few plants other than lettuce will do well in this type of system.
This type of hydroponic system is great for the classroom and is popular with teachers. A very inexpensive system can be made out of an old aquarium or other water tight container. The biggest drawback of this kind of system is that it doesn’t work well with large plants or with long-term plants.
EBB & FLOW SYSTEM – (FLOOD AND DRAIN)
The Ebb and Flow hydroponic system is an active recovery type system. The Ebb and Flow uses a submersible pump in the reservoir and the plants are in the upper tray. They work on a simple flood and drain theory. The Ebb and Flow system works by temporarily flooding the grow tray with nutrient solution and then draining the solution back into the reservoir. This action is normally done with a submerged pump that is connected to a timer. The reservoir holds the nutrient solution and the pump.
When the pump turns on, the nutrient solution is pumped up to the upper tray and delivered to the root system of the plants. The pump should remain on for about 20 to 30 minutes, which is called a flood cycle. Once the water has reached a set level, an overflow pipe or fitting allows the nutrient solution to drain back into the reservoir. The pump remains on for the entire flood cycle. After the flood cycle the nutrient solution slowly drains back down into the reservoir through the pump. During the flood cycle oxygen poor air is pushed out of the root system by the upward moving nutrient solution. As the nutrient solution drains back into the reservoir, oxygen rich air is pulled into the growing medium. This allows the roots ample oxygen to maximize their nutrient intake.
The Timer is set to come on several times a day, depending on the size and type of plants, temperature and humidity and the type of growing medium used.
The Ebb & Flow is a versatile system that can be used with a variety of growing mediums. The entire grow tray can be filled with Grow Rocks, gravel or granular Rockwool. Many people like to use individual pots filled with growing medium, this makes it easier to move plants around or even move them in or out of the system.
The main disadvantage of this type of system is that with some types of growing medium (Gravel, Growrocks, Perlite), there is a vulnerability to power outages as well as pump and timer failures. The roots can dry out quickly when the watering cycles are interrupted. This problem can be relieved somewhat by using growing media that retains more water (Rockwool, Vermiculite, coconut fiber or a good soilless mix).
The Ebb & Flow system is very versatile and can be used with a variety of growing mediums. The grow tray can be loaded with gravel, grow-rocks or rock wool…
The Ebb and Flow is low maintenance, yet highly effective type of hydroponic gardening.
DRIP SYSTEMS RECOVERY / NON-RECOVERY
Drip systems are probably the most widely used type of hydroponic system in the world.
The Continuous Drip system is an active recovery or non-recovery type system. This system uses a submersible pump in a reservoir with supply lines going to each plant. With drip emitter for each plant the gardener can adjust the amount of solution per plant. A drip tray under each row of plants, sending the solution back to the reservoir, can easily make this system an active recovery type. In the early days of hydroponics, the extra solution was leached out into the ground. Continuous Drip systems are often used with Rockwool. Although, any growing medium can be used with this system, thanks to the adjustment feature on each individual drip emitter.
Operation is simple; a timer controls a submersed pump. The timer turns the pump on and nutrient solution is dripped onto the base of each plant by a small drip line. In a Recovery Drip System the excess nutrient solution that runs off is collected back in the reservoir for re-use. The Non-Recovery System does not collect the run off.
A recovery system uses nutrient solution a bit more efficiently, as excess solution is reused, this also allows for the use of a more inexpensive timer because a recovery system doesn’t require precise control of the watering cycles. The non-recovery system needs to have a more precise timer so that watering cycles can be adjusted to insure that the plants get enough nutrient solution and the runoff is kept to a minimum.
The non-recovery system requires less maintenance due to the fact that the excess nutrient solution isn’t recycled back into the reservoir, so the nutrient strength and pH of the reservoir will not vary. This means that you can fill the reservoir with pH adjusted nutrient solution and then forget it until you need to mix more. A recovery system can have large shifts in the pH and nutrient strength levels that require periodic checking and adjusting.
N.F.T. (Nutrient Film Technique)
The Nutrient Film Technique or NFT system is an active recovery type hydroponic system.
This is the kind of hydroponic system most people think of when they think about hydroponics. N.F.T. systems have a constant flow of nutrient solution so no timer required for the submersible pump. The nutrient solution is pumped into the growing tray (usually a tube) and flows over the roots of the plants, and then drains back into the reservoir. The nutrient solution flows over the roots up to 24 hours per day.
The plants are held up by a support collar or a grow-basket and no growing medium is used. There is usually no growing medium used other than air, which saves the expense of replacing the growing medium after every crop. Plant is supported in a small plastic basket with the roots dangling into the nutrient solution.
Oxygen is needed in the grow-tube so capillary matting or air stones must be used. The NFT system is very effective. Although, many novice hydroponic growers find it difficult to fine tune. N.F.T. systems are very susceptible to power outages and pump failures. The roots dry out very rapidly when the flow of nutrient solution is interrupted. It can also be very unforgiving, with no growing medium to hold any moisture, any long period of interruption in the nutrient flow can cause the roots to dry out and the plants to suffer and possibly die.
The aeroponic system is probably the most high-tech type of hydroponic gardening. Like the N.F.T. system above the growing medium is primarily air. The roots hang in the air and are misted with nutrient solution. The mistings are usually done every few minutes. Because the roots are exposed to the air like the N.F.T. system, the roots will dry out rapidly if the misting cycles are interrupted.
A timer controls the nutrient pump much like other types of hydroponic systems, except the aeroponic system needs a short cycle timer that runs the pump for a few seconds every couple of minutes.
In this system, plant roots are misted with water and nutrients, while getting oxygen directly from the air. Aeroponics has been proven and refined for decades and is used by scientists around the world, including NASA. Using Aeroponics, plants:
- receive their required daily nutrients.
- avoid contact with soil borne pests and fungus.
- grow up to 50% faster.
The opportunity to grow fresh fruits and vegetables outside of the soil, indoors or outdoors, is becoming not only a distinct advantage, but also a necessity. While we have learned much about this exciting method of growing, the benefits of Aeroponics are still largely untapped. It is believed that Aeroponics will soon be the most commonly used growing technique worldwide.