Deep water culture

Deep water culture (DWC) is a hydroponic method of plant production by means of suspending the plant roots in a solution of nutrient-rich, oxygenated water. Also known as deep flow technique (DFT), floating raft technology (FRT), or raceway, this method uses a rectangular tank less than one foot deep filled with a nutrient-rich solution with plants floating in Styrofoam boards on top. This method of floating the boards on the nutrient solution creates a near friction-less conveyor belt of floating rafts. DWC, along with nutrient film technique (NFT), and aggregate culture, is considered to be one of the most common hydroponic systems used today. Typically, DWC is used to grow short-term, non-fruiting crops such as leafy greens and herbs. The large volume of water helps mitigate rapid changes in temperature, pH, electrical conductivity (EC), and nutrient solution composition. Deep water culture has also been used by hobby growers. Net pots, plastic pots with netting to allow roots to grow through their surface, are filled with a hydroponic medium such as Hydroton or Rockwool to hold the base of the plant. In some cases net pots are not needed. 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 or 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, frequent monitoring must be kept of the nutrient solution to ensure that it remains in the uptake range of the crop. A pH that is too high or too low will make certain nutrients unavailable for uptake by plants. Generally, the best pH for hydroponic crops is around 5.5–6.0. In terms of EC, too low means that there is a low salt content, usually meaning a lack of fertilizer, and an EC that it too high indicates a salt content that could damage the roots of crops.