Since plants may be grown hydroponically with or without a growing medium, hydroponic systems therefore can be categorized into two: aggregated and non-aggregated. Categorizing the different hydroponic systems will help organize out thoughts for better comprehension. In aggregated systems, the plants are positioned within the medium, in a container. The container is then fixed on the platform. In non-aggregated systems, the plants are fixed directly on the platform.
Further, the different systems may be grouped into two types: static and dynamic. A system is considered to be static when the nutrient solution is not continuously or continually supplied. Otherwise, the system is considered dynamic.
1.0 Static Type
1.1 Deep Water System (Water Culture)
Design description: The NS is placed in the growing tub to a suitable level such that about half of the root system is submerged into the solution. In this system, the growing tub serves, at the same time, the purpose of the reservoir. This technique works for both aggregated and non-aggregated systems.
1.2 Wick System
Design description: This system works under the principle of capillary action where NS is drawn to the root system via a wick (any inert porous material). Similar to the deep water system, the growing tub may be at the same time, the reservoir.
1.3 Raft System
Design description: the plants are fixed on a piece of buoyant material (usually inert plastic material) and are floated on the nutrient solution. When necessary, holes with suitable diameter are drilled on the platform to allow plants to move as solution level changes. In some cases, the buoyant material serves the purpose of the platform at same time.
2.0 Dynamic Type
2.1 Nutrient Film Technique (NFT)
Design description: The growing tub is positioned to follow the required slope. The thickness or the root mat that forms at the bottom of the tub shall dictate the slope required such that about half of the root mat is submerges into the flowing solution and that the upper surface of the root mat is exposed to air. The NS enters the growing tub from the upstream by gravity (manual) or by pump (automated). The NS may be recycled, when necessary, by directing the NS back to the reservoir. This technique works for both aggregated and non-aggregated systems.
2.2 Ebb and Flow (Flood and Drain)
Design description: The growing tub is temporarily flooded with NS to a suitable level (usually, where the entire root system becomes submerged) and then draining back the NS to the reservoir. A drain valve is usually utilized to regulate the discharge flow and to provide the roots suitable time to absorb the nutrients. Flooding can be done manually (by gravity) or automatically (by pump with timer). This technique works for both aggregated and non-aggregated systems.
2.3 Drip System
Design description: NS is dripped into the root system (at the base) of the plant. The amount of the NS required by each plant is predetermined before the drip line is activated. In efficient drip systems, there are usually no excess NS. This system works for aggregated systems.
2.4 Run-to-waste
Design description: The NS is continually flushed (manually or automatically) into the growing tub. Since the required amount of NS is not determined prior to flushing, excess (run off) NS is drained outside the system. The excess is not recovered or recycled for reuse within the system. In some cases, the excess is collected for other purposes.
2.5 Aeroponics
Design description: NS is continually (at suitable short cycles) misted into the root system of plants. The system employs a pump with short cycle timer. This works for non-aggregated systems. NOTE: since, water is used to transmit the nutrients to roots, it is reasonable to consider aeroponics as one of the hydroponic systems.