Three Types of Hydroponic Growing

Interested in growing some of your cannabis hydroponically? There are three distinct techniques that are popular with experienced growers: deep water culture, ebb and flow, and the nutrient film technique. Each has its advantages and disadvantages. But they are proven systems fully capable of producing high quality crops with high yields. Choose a method based on your personal preferences and the materials you have available to construct your system or those you can purchase from a hydroponics dealer.

Deep water culture

With deep water culture (DWC), roots hang in a nutrient-rich, oxygenated water solution. There are three common methods:

1. The traditional DWC method germinates seeds in small blocks of rockwool and places them in small plastic baskets. The baskets are filled with expanded clay pellets and suspended from holes cut in the lids of individual buckets, which are filled with a hydroponic nutrient solution. To generate oxygen for the roots, an aquarium air stone is placed at the bottom of each bucket, connected to an air pump.
2. In recirculation deep water culture (RDWC), a large reservoir holds the oxygenated nutrient solution, which is pumped to each bucket through one line and pumped back to the reservoir through another at a constant rate of flow. However, there’s a delay in the amount of time it takes the roots of newly germinated plants to grow through the rockwool and down through the expanded clay pellets to reach the nutrient solution. This can cause a delay in early growth stages.
3. In “Bubbleponics,” incoming nutrient solution is introduced at the top of the basket. The plants grow much faster during the initial stages and continue doing so throughout the growth cycle. This method can produce large yields of high quality buds in a short amount of time.

Ebb and flow

Another method, very similar to RDWC, is ebb and flow. A large reservoir holds the hydroponic nutrient solution, and a small submersible pump sends the solution to a small distribution reservoir where it is then distributed to two or more buckets via small hoses. An electronic timer controls both the incoming and the outgoing pumps:

•  The incoming pump causes the distribution reservoir to fill, and gravity forces the nutrient solution out through hoses to the buckets; this causes them to fill but prevents them from overflowing.
• The timer also causes the outgoing pump to remove water from the distribution reservoir and the buckets and deposit it back into the main reservoir, where it can be re-oxygenated before redistribution.

Ebb and flow requires less nutrient solution, due to the presence of the expanded clay pellets. But it has one major disadvantage: The entire root system permeates the pellets. Removing them from the roots after harvest can be difficult and time-consuming.

Nutrient film technique

The third hydroponic method is the nutrient film technique (NFT), in which holes are cut along the length of one side of a large-diameter tube. Both ends are capped, and the tube is positioned at an incline using a support system. The plants are germinated in rockwool pellets and placed in small plastic baskets, which are filled with expanded clay pellets and then suspended in the holes. Then, a constant stream of hydroponic nutrient solution is fed into the elevated end of the tube. It runs downhill to the lower end, where it then drains through a hose into a reservoir so that it can be pumped back to the top of the tube for recirculation.

However, the tube should have a sufficient incline to prevent the water from pooling, but not so much that it runs any faster than necessary. In addition, only enough solution is pumped to the top of the tube to create a thin film downward, so that the plant’s root system will spread out along the bottom of the tube and expose the upper sections to air where they can readily absorb oxygen. NFT can be a very productive method of cannabis cultivation when it’s constructed, operated and managed correctly.

By Bill Bernhardt