Hydroponic gardening is defined as growing without soil. In place of soil, hydroponic systems must use some sort of substrate and a network to deliver the liquid nutrients to the roots. There are several different types of hydroponic systems; each with their own advantages and disadvantages. There are also hybrid systems, which combine attributes from more than one type of hydroponic system or combine a living soil with the automated nutrient delivery of a hydroponic system.
Commercial growers and home hobbyists alike are enjoying the benefits of hydroponic gardening. Although there are many variations of hydroponic systems, the vast majority of hydroponic growers use one following systems:
Nutrient Film Technique
Nutrient film technique, or NFT, is one of the most commonly used systems in commercial greenhouses for growing lettuce and other greens. NFT is also popular among hydroponic hobbyists. NFT is a system that supplies a plant’s roots with a continuous flow of nutrient solution through a series of tubes or gutters. The “film” is referring to the thin layer of nutrient solution that covers the bottom of each tube or gutter. The tubes or gutters are positioned at slight angles, allowing gravity to return the nutrient solution to the reservoir or the subsequent tube or gutter.
Finishing large plants in NFT systems can be difficult because large plants have large root masses. Oversized roots in a NFT system can be cumbersome and may clog tubes or plug gutters.
Best crops for NFT: Lettuce, spinach, strawberries, blueberries, mints, basil, chives, sage.
Wick systems are popular because they are very efficient and effective. Wick systems rely on capillary action to deliver nutrient solution to the plant’s roots. Plant containers are set in a tray or container above the nutrient reservoir. The wicking material is placed between the reservoir and the tray/container. Various materials can be used, including natural fibers, like cotton or hemp. Synthetic materials, such as nylon or acrylic, are also commonly used as a wicking material. One major advantage of wick systems is that they do not require electricity to deliver water or nutrients to the plants. Mediums like coco fiber are commonly used but wick systems can also utilize an organic soil as its medium thus creating a hybrid hydroponic system. Wick systems work well with a wide variety of greenhouse vegetable crops.
Best crops for wick system: Mints, basil, chives, sage, lemon balm, rosemary, tarragon, beans, spinaches, kales, lettuce, celery, and bok choy.
A top feed, or top drip, hydroponic system is a setup where a feed line is directly attached to the base of each plant. A pump, normally controlled by a timer, intermittently supplies each plant with nutrient solution. Systems can be set up as a run-to-waste or as a recirculating system where the nutrient solution is recycled. Top feed systems are very popular for commercial tomato growers, especially those using rockwool as the medium. Rockwool cubes, net pots or mesh-bottomed planting containers all work well in a top-drip system. Just about any medium is compatible with a top-feed system but many growers prefer clay pebbles or rockwool. Top feed systems also work well with a wide variety of greenhouse vegetable crops.
Best crops for top feed: Tomatoes, beans, spinaches, kales, cucumbers, radishes, lettuce, celery, bok choy, peppers, strawberries, mints, basil, chives, sage, lemon balm, rosemary, tarragon
Flood and Drain
Flood and drain, also known as ebb and flow, hydroponic systems are another popular choice among both commercial and hobby gardeners. A flood and drain system utilizes a table or trough that is flooded with nutrient solution for a given period of time and then drained. To avoid the need for a second pump, traditional flood and drain systems use gravity to return the nutrient solution to the reservoir.
Flood and drain systems work well for beginner gardeners or hobbyists looking to experiment with hydroponics because they are easy to build and a wide range of media can be used. Flood and drain systems can also offer a hybrid soil/hydroponic system to growers who are not ready to give up soil gardening completely, but still want to gain some of the benefits hydroponic gardening has to offer. In a hybrid system, a grower gets the forgiveness of a living soil and the speed of hydroponics.
Best crops for flood and drain: beans, spinaches, kales, cucumbers, radishes, tomatoes, lettuce, celery, bok choy, peppers, mints, basil, chives, sage, lemon balm, rosemary, tarragon.
Deep Water Culture
Deep water culture, or DWC, is a system in which the plant’s root mass is mostly submerged in water and additional oxygen is delivered via an air pump. When water temperatures are kept between 65-70 degrees F, this system encourages particularly fast growth, which is unmatched by almost any other hydroponic system. A simple DWC system can be made from a 5 gallon bucket and a net-pot bucket lid. The plant is placed in the net pot lid. Clay pebbles are typically used as the media but only for stabilization. Since the majority of the root mass reaches downward and is suspended in the nutrient solution, the medium isn’t part of the nutrient delivery. Oxygen is supplied to the roots via a small aquarium air pump.
The downfall of DWC systems is water temperature fluctuation. Fluctuating water temperature is unforgivable in this system, especially when temperatures exceed 75 degrees F. As the water gets warmer, it loses its ability to hold dissolved oxygen. This, in turn, leaves a plant’s root mass susceptible to anaerobic pathogens.
Best crops for DWC: Tomatoes, beans, cucumbers, lettuce, peppers, strawberries.
Aeroponics and Fog Systems
Aeroponic and fog systems are hydroponic systems that sporadically spray or mist a plant’s root mass with nutrient solution. Aeroponic systems generally utilize spray nozzles to create small droplets of nutrient solution. Some aeroponic systems create a “dry fog” by reducing the droplet size to as small as 5 microns, hence the term “fog system”.
It is absolutely imperative to use a fully soluble nutrient solution with these systems. Nutrient solutions that are not fully soluble will leave residue and eventually clog the misters or spray heads.
There is more maintenance involved with an aeroponic system than other hydroponic systems. Checking and cleaning spray heads or misters must be done on a regular basis. Due to the increased maintenance, aeroponic systems are usually avoided by novice growers and hobbyists.
Best crops for aeroponics: Lettuce, peppers, strawberries, mints, basil, chives, sage, lemon balm, rosemary, tarragon, beans, spinaches, kales.
Vertical Hydroponic Systems
Vertical hydroponic systems are systems which utilize soilless gardening in a vertical position. Most vertical hydroponic systems are recirculating systems which means the nutrient solution is collected and reused after each feeding. The nutrient solution is commonly delivered to the upper most plant module so gravity can bring the solution to the remaining plants down below. The most common types of hydroponic systems used in vertical gardening are NFT, top feed, and aeroponics. Vertical hydroponic systems combine the speed of growth associated with hydroponic gardening and the space maximizing benefits of vertical gardening.
Best crops for vertical hydroponic systems: Strawberries, lettuce, spinaches, mints, basil, chives, sage, lemon balm, rosemary, tarragon.