Cultivating plants without the use of soil--using a nutrient solution to provide the plants' growing needs--is call hydroponic growing. Hydroponics allows growers to plant in areas where environmental conditions, poor soil or insufficient space have made growing in traditional ways difficult or impossible. Growing hydroponically allows the grower to control the growing environment, and allows large production in a small space.
Hydroponic System Requirements
Soil-less gardening requires a nutrient solution, a way to transport the nutrient solution to the plant and a structure that holds the plant in place. Light is also required. How the plant gets light depends on where the hydroponic system is placed. If it is outdoors, sunlight will provide what the plant needs. Indoor hydroponic systems require a grow light to provide enough light for the plant to produce food for itself.
The nutrient solution is the most important element for hydroponic plant growth. Traditional fertilizers put into soil, says the Virginia Cooperative Extension, do not need to include all 13 elements that a plant requires to live, because the soil provides small amounts of these. Hydroponic solutions have to provide all the elements, however, and are specially formulated to do so. Nutrient solutions are sold in concentrates that require mixing before being put into the system. Once mixed, the nutrient solution is diluted in water until the pH (the acidity or alkalinity) has a reading of between 5 and 6.
Water Culture Systems
Water culture systems are one subset of methods used to grow plants hydroponically. These include the nutrient film technique, aeroponics and the aeration method.
Nutrient film suspends the plants in a plastic trough or tube that provides a steady, thin film of nutrient solution to the plant roots. The trough is set at an angle to drain the solution down into a reservoir. A pump pushes the solution back to the top.
Aeroponics uses a fine mist of nutrient solution to spray the roots of the plants in a system. Plants are placed in holes in a triangular pattern that hold the plant in place at an angle. Spray heads, like a sprinkler system, placed inside the triangles spray nutrient solution onto the plant roots at regular intervals.
Aeration uses an air pump to bubble oxygen through a nutrient solution, moving it around plants suspended 1 inch above it in wire pots. The nutrient solution touches the roots of the plants as it bubbles up. Plants are kept in a growing medium such as vermiculite or perlite to catch the nutrient solution.
Aggregate systems are another method of hydroponic growing. They consist of a structure that holds the plants in place, filled with a growing medium such as perlite, vermiculite, sand, rockwool, gravel or clay pebbles. The medium holds the plants in place and absorbs small amounts of the nutrients. Flood-and-drain, trickle-feed and tube culture are all popular methods of growing using the aggregate method.
According to the Alabama Cooperative Extension Service, most fruiting plants require between 8 to 10 hours of light a day. A hydroponic system that is set indoors will require grow lamps to provide this requirement. Grow lamps are available as meta-halide bulbs, high pressure sodium bulbs, fluorescent bulbs and LEDs. Lights are available at garden centers or online retailers.