Hydroponics, the practice of growing plants without the use of soil, uses specific water delivery processes to deliver nutrients directly to plant roots. Hydroponics includes a number of different systems, but each follows a general process resulting in the growth of a plant or plants within that system.
Hydroponic systems fall into two broad categories: passive and active. Within a passive system, the water is funneled into the inert material, such as a mixture of perlite and sand, in which the plants are anchored. The water floods through the mixture, and the roots take up the nutrients as the water flows back into the reservoir. An active system employs pumps and tubing to force water over or around the roots, immersing them temporarily before returning to the reservoir.
In both passive and active systems, the key process is the exposure of plant roots to nutrient-rich water, allowing the roots to take up the necessary elements for growth and production. Throughout all phases of the hydroponic process, water must be delivered to the roots; the roots do not search out water and nutrients as they do when anchored in soil.
A seed is inserted into a cube of rockwool or other inert material. The cube is then placed in a small container of pH-balanced water. The seed germinates, resulting in a seedling in the inert medium. A small amount of nutrient solution, approximately 1 part to 4 parts water, is added to the water to feed the seedling roots. After a few days, the seedling is placed in an appropriate hydroponic system.
The reservoir is one part of any hydroponic system. The reservoir may be included in the same container that holds the plants, as is sometimes seen in the Dutch bucket systems, or it may be a separate component. In either instance, the reservoir contains a sufficient supply of nutrient-enriched water. Microbes naturally present in the water become a part of a symbiotic relationship between water, added nutrients and the plant roots. This relationship resembles the relationship established when a seedling is planted in soil.
As water is delivered to plant roots, the plant roots take up nutrients as the water passes over them and circulates back to the reservoir. Over a brief period of time--two to three weeks--the nutrient supply in the water becomes depleted, and the reservoir must be replenished with pH-balanced water and a fresh supply of nutrients. The ebb-and-flow cycle of water delivery remains consistent, with the hydroponic gardener continually providing the correct balance of water and nutrients to meet the specific needs of any given plant or plants.