Deep water culture
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Deep water culture (DWC) is a hydroponic, and so also aquaponic, method of plant production by means of suspending the plant roots in a solution of nutrient-rich, oxygenated water. Also known as raft or float systems, this method uses floating rafts to suspend plant roots into a pool of water about 1 foot in depth. Since there is no media to capture and process the solid wastes, filtration techniques must be built into the design. This necessitates more advanced aquaculture techniques and system requirements, leading to higher upfront costs. Bubbleponics is a related method of plant production that involves a top-fed deep water culture system.
Early Deep Water Culture (DWC) systems consisted of a five-gallon bucket, air stone, air pump and net pot with a medium. Five gallon buckets were the favorite of many early adopters of the system as they were readily available at hardware stores. Net pots come in three sizes: 6", 8" and 10". Net pots are then filled with a hydroponic medium such as Hydroton and a Rockwool cube is added in the center that holds the base of the plant. For Oxygenation of the hydroponic solution, an airstone is added. This air stone is then connected to an airline that runs to an air pump.
As the plant grows, the root mass stretches through the rockwool and hydroton into the water below. Under ideal growing conditions, plants are able to grow a root mass that comprises the entire bin in a loosely packed mass. As the plant grows and consumes nutrients the pH and EC of the water fluctuate. For this reason, constant tabs must be kept on the nutrient solution to ensure that it remains in the uptake range of the crop.
Recirculation deep water culture
Traditional methods using unconnected buckets require each bucket to be tested for pH and conductivity factor (CF) individually. This has led to the creation of Recirculation Deep Water Culture (RDWC) systems. Rather than having individual buckets, RDWC bins are linked together most commonly using a PVC pipe. A pump is also added at the front of the system that pulls water through a line from rear of the system into a control bucket. This return line generally has a spin filter on it that cleans particulate from the water before it reaches the pump. the individual bins, including the control are aerated
Because the system is linked together, adjustments can be made to the pH and EC through the control bucket allowing the operator to save time and maintain consistency in the nutrient solution. Potential issues with the system stem from a lack of understanding how to keep it clean or allowing the solution to get too warm.