Hydroponic methods vary widely while accomplishing the same goal. The hydroponic method must keep the plant moist while allowing access to air, as well. Hydroponic methods approach this goal in different ways, with varying water to air ratios, and no one method is best for all plants.
Hydroponic methods are divided into two main categories: active and passive. Active systems rely air and water pumps to nourish the plants. Passive systems rely on the gardener to water the plants on time, or use a wick or gravity to deliver the nutrients.
The simplest hydroponic method is the wick system. Water and nutrients are kept in a reservoir and are wicked up into the growing medium. Wick systems are inexpensive and may not be able to supply optimum amounts of moisture as the plants grow.
In the water culture method, plants grow in pots on a floating platform above the nutrient solution. The solution is aerated using a bubble stone to keep oxygen levels high. Plant roots dangle into the water, taking moisture, nutrients and oxygen from the water. Leaf lettuce does well in water culture, but the system is too wet for most plants.
Flood and Drain
The flood-and-drain method waters the plants by periodically pumping nutrient solution into the reservoir. The solution drains away, leaving the roots moist. Most flood and drain systems are active systems, but the method can be used passively by hand-watering the plants on schedule throughout the day.
The drip method is a simple system that is widely used. Nutrient solution is dripped into the container for each plant. Excess nutrients drain away and can be collected for reuse. The drip system is an active system, requiring a pump to deliver the nutrient solution. The advantage of the drip system is that the amount of moisture delivered to the plant can be controlled, and additional plants can be easily added to the system by installing another drip line.
Nutrient Film Technique
The nutrient film technique method (NFT) is another active method. Growing trays or beds are built at a slight angle to allow the nutrient solution to flow across the bottom of the bed. The plant roots dangle into this flowing stream of nutrients. NFT plants are usually grown in a small plastic basket or net pot without growing medium, allowing the roots to grow through the holes in the basket directly into the nutrient stream.
The Aeroponic Method
The aeroponic method allows the plants to grow in air. The roots dangle from the net pot or basket into a fine mist of nutrient solution. A pump and timer mists the roots every few minutes to keep them moist and fed. The misting must continue uninterrupted or the roots will dry out. Aeroponic growing is highly successful in the hands of an experienced gardener and a reliable source of electricity.