Hydroponics was originally defined as ?the cultivation of plants in water?, however, with the successful use of the technique for cultivating plants in air and other media besides water, the definition was changed to the more inclusive - ?the cultivation of plants without soil.? Hydroponic techniqueshave proved effective for commercial cultivation and also in home gardening. Hydroponic techniques and systems have greatly benefited agriculture especially where, conventional soil cultivation is not possible due to unavailability of agricultural land, resources or other factors.



Hydroponic Systems & Techniques

The science of hydroponics has evolved since its inception with the development of two main systems ? the water based hydroponic systems and aggregate based hydroponic systems. Water based hydroponic systems use water around the plant roots for delivery of nutrients. In aggregate based systems, plant roots are supported in some kind of inert material such as rockwool, pebbles etc. Both Water Culture Hydroponic Systems and Aggregate based Hydroponic Systems may use one of several different techniques of nutrient delivery to plant roots depending on requirements particular to the system.

Water Culture Systems

Water culture systems use water for delivery of nutrients which can be delivered to plant roots in different ways. Several techniques can be used; some of the more common of these are -

Nutrient Film Technique

In nutrient film technique a plastic trough or tube is used as the container through which a thin film of nutrient solution is made to flow continuously. Plants are grown out of holes on the top of the tube with their roots in the trough. The thin film of nutrient flows constantly past the roots. The trough is positioned to slope gently in order to maintain the circulation of the nutrient solution through the nutrient reservoir, to the plant roots and back. This is a popular technique with the home gardener and comes in many variations.

Aeroponics makes use of a nutrient mist delivered to the roots by a vaporizer or some other means. An A shaped frame constructed out of Styrofoam boards forms the support-base for plants. The plants are placed in holes on the inclined sides of the frame with the roots reaching out through the holes. The nutrient mist sprayed inside the A frame which then settles on the roots from where it is absorbed by the plant. Excess nutrient runs down the frame, is collected and recycled.

The aeration method was one of the first hydroponic techniques to be developed. In this method plants are suspended 1 inch above a nutrient solution collected in a container. An aquarium air pump is used to bubble oxygen through the nutrient solution. The plants are carried in a 2-inch deep mesh tray that fits inside the container when the lip of the tray is placed over the container's edge. Gravel, clay pebbles or vermiculite filled in the tray serves to hold the plants and at the same time allow the roots to grow down into the nutrient solution.

Aggregate Systems

Aggregate systems use inert materials such as rockwool, clay pebbles, gravel, etc. to support plant roots. The inert media serves to support the plant and also allows good oxygen penetration to the roots in addition to retaining a thin film of nutrients and water.

The flood and drain method is the most commonly used aggregate system. In this system a container is filled with aggregate and plants which is then flooded with a nutrient solution. The solution is then drained back into the nutrient reservoir by opening a valve at the bottom of the container. The roots should be submerged for not more than 20 -30 min. during each cycle.

Another widely used aggregate system is the trickle feed method. The nutrient solution is continuously pumped from a reservoir through a 1/2-inch irrigation tube. This tube branches into several 1/8-inch tubes that feed the solution to containers carrying the aggregate and plants. Solution that may be in excess gets collected at the base of each container and is then returned to the nutrient reservoir.

Hydroponic systems offer several advantages over conventional soil based systems of growing plants. They afford better manage over plant growth eliminating weeds and soil borne diseases. Many hydroponic systems also optimize plant nutrition helping grow better crops more economically.