This page has been designed to help answer the important questions beginning growers might have when just getting started in hydroponics. A lot of these concepts are connected to each other. Follow the links and put the pieces of this growing puzzle together.
The more you know, the easier it is to grow!
During photosynthesis, plants use carbon dioxide (CO2), light, and hydrogen (usually water) to produce carbohydrates, which is a source of food. Oxygen is given off in this process as a by-product. Light is a key variable in photosynthesis.
Measuring nutrient solution strength is a relatively simple process. However, the electronic devices manufactured to achieve this task are quite sophisticated and use the latest microprocessor technology. To understand how these devices work, you have to know that pure water doesn’t conduct electricity. But as salts are dissolved into the pure water, electricity begins to be conducted. An electrical current will begin to flow when live electrodes are placed into the solution. The more salts that are dissolved, the stronger the salt solution and, correspondingly, the more electrical current that will flow. This current flow is connected to special electronic circuitry that allows the grower to determine the resultant strength of the nutrient solution.
The scale used to measure nutrient strength is electrical conductivity (EC) or conductivity factor (CF). The CF scale is most commonly used in hydroponics. It spans from 0 to more than 100 CF units. The part of the scale generally used by home hydroponic gardeners spans 0-100 CF units. The part of the scale generally used by commercial or large-scale hydroponic growers is from 2 to 4 CF. (strength for growing watercress and some fancy lettuce) to as high as approximately 35 CF for fruits, berries, and ornamental trees. Higher CF values are used by experienced commercial growers to obtain special plant responses and for many of the modern hybrid crops, such as tomatoes and some peppers. Most other plant types fall between these two figures and the majority is grown at 13-25 CF.
Nutrient Film Technique.
The purist form of today’s highly developed hydroponic growing systems is Nutrient Film Technique (N.F.T.). It is also the form of hydroponics most intriguing to the public because of its futuristic nature and appearance. The nutrient is fed into growtubes where the roots draw it up. The excess drains by gravity back to the reservoir. A thin film of nutrient allows the roots to have constant contact with the nutrient and the air layer above at the same time.
Drip-Irrigation or Micro-Irrigation
Today’s greenhouse irrigation systems employ, to an ever-increasing extent, the concept of drip or microirrigation. It entails a principle of minimized water consumption with maximized plant benefit. There are literally hundreds of emitting/dripping/trickling/micro-spraying/etc. devices on the market today for the commercial/hobbyist grower to choose from. A submersed pump feeds nutrients solution through header tubes to secondary feed lines connected to drip emitters. A controlled amount of solution is continuously drip-fed over the medium and root system. Another tube is connected to the lower part of the garden system to recover the solution.
Aeroponics / Deep Water Culture
Plant roots are suspended in highly oxygenated nutrient solution allowing easy inspection and pruning of roots. Air pumps, compressors or Oz injectors provide oxygen which is crucial to healthy plant growth. The simplicity and affordability of these very active systems make them popular with home hobbyists and commercial growers alike.
In an Aeroponic system the roots are misted within a chamber. A pump pushes the water with nutrient solution through sprayers, keeping the roots wet while providing a maximum amount of oxygen.
This technique is an excellent way to propagate cuttings.
Deep Water Culture is another form of aeroponics. The root system of a plant grown in Deep Water Culture is immersed in water with a bubbling aerator keeping the roots oxygenated.
This technique is very good to use with plants that are heavy feeders.
Flood & Drain
Flood & Drain systems are similar to N.F.T. systems. They are ideal for multiple plant per square foot growing where individual plant inspection is difficult. They are also very popular as propagation tables. A plastic growing tray is flooded periodically by a submersed pump connected to a digital timer (or the ControlFreak!). Medium and root system are soaked, then drained (via gravity back through the pump) at
specific intervals. Various mediums can be used, Rockwool is the most popular with Flood & Drain systems.
The Ebb & Flow trays are examples of the Flood & Drain system.
Home Hobbyist Systems
There are a number of compact hydroponic systems and kits most popular with home hobbyists, researchers and teachers. These are made to be especially attractive to children in order to get their attention and interest. Hobby systems include deep water and aeroponic systems which are scaled down versions of commercial systems.
Passive Planters / Hydroculture
This is probably the most commonly know form of hydroponics. These systems do not require a water or air pump and are therefore called passive systems. Passive Planters have been used in office buildings and restaurants for many years.
Hydroculture planters utilize a clean, porous growing medium to support plant roots. A nutrient reservoir in the base of the growing container allows the plants to take as much or as little water as they require. Water level indicators show exactly when and how much to water. Clean, odourless and non-allergenic, hydroculture or passive planters are ideal for every environment.