The Lowdown on Hydroponics
New to hydroponics? No problem.
Plants have pretty basic needs: oxygen, nutrients, water, sun, and structure to support the roots.
With hydroponics, we find new ways of providing plants with what they need to grow. The systems described below are the most common hydroponic methods for growing plants, indoors and out.
The wick system is a form of passive hydroponics with no moving parts, making it one of the most simple hydroponic growing method. Plants are grown in an inert medium, such as perlite or coconut husk (coir) that absorbs or “wicks” nutrient solution from a reservoir, providing a constant supply of water and food to the plant’s roots.
Our Intro to Hydroponics workshops demonstrate how to construct your own wick system with repurposed soda bottles. Contact us for information about the next workshop to build your own planter!
Water culture systems are the simplest form of active hydroponics. Plant roots grow directly in the water reservoir and are supplied oxygen with an air pump. Water culture systems can be built from repurposed glass mason jars, plastic buckets, or tubs as the reservoir container, with the plant suspended from the lid in a net pot, letting the roots grow through the holes into the water below. You can build your own water culture system in our Intermediate Hydroponics workshop.
In larger, commercial scale designs, several plants are placed in a sheet of buoyant material that floats on nutrient solution like a raft. Water is generally held in a separate, larger reservoir and pumped up to the floating grow bed and then drained back down to the reservoir in a constant cycle. Our systems at CDSC are a great example of raft system water culture in action.
A drip system is another type of active hydroponics, similar to water culture method. In addition to having the roots suspended directly in water -like in a water culture system, nutrient solution is dripped onto the base of each plant stem, hydrating upper parts of the root system. The excess nutrient solution that isn’t used by the plant can be collected back into a reservoir for re-use (recovery system). Recycling excess nutrients is not necessary, drip systems can be built so that excess nutrients drain out directly onto a soil garden underneath (non-recovery system). The fence boxes built at the Bushwick Campus Farm are an example of non-recovery drip system.
Flood and Drain
Also known as the Ebb and Flow technique, this method was developed in World War II to grow tomatoes and lettuces for American troops in the Pacific. It was particularly effective for its low water usage, speedy plant development, and that the volcanic rock available on the islands was an ideal growing medium.
Plants are sown directly in a tray filled with growing medium. At intervals regulated by a timer, a water pump fills the tray with nutrient solution from a separate reservoir, saturating the growing medium and plant roots. The water begins to recirculate back into the reservoir through a one-way overflow valve. When the timer turns the pump off, the tray drains completely, providing the roots with oxygen.
This method is commonly used for flowering plants such as tomatoes and peppers because it easily supports large root development. The systems we built with the clients at Fountain House feature the Flood and Drain method.
Nutrient Film Technique (NFT)
NFT or continuous-flow solution culture, plants are suspended and the roots grow down into a shallow, constant stream of nutrient solution pumped into the system from a separate reservoir. The parts of the roots that are not in the stream of water absorb oxygen for the plant. The channel containing the plants is built at an angle to use gravity to recycle nutrient solution back into the main reservoir. NFT systems scale well, as one central reservoir can hydrate several channels of plants.
In an aeroponic system, plant roots are suspended in air and saturated with a constant mist of nutrient solution. An advantage of using aeroponics is that suspended plants receive 100% of the available oxygen and carbon dioxide at the root zone, as well as the stems and leaves, which accelerates plant growth. NASA has been researching aeroponic techniques as a possible method for growing food in space, as a nutrient solution mist is more manageable than liquid in a zero-gravity environment.