Known as soilless gardening, hydroponics has a long history in human civilization. We may have gotten down its science as late as the 1890s, but the method has actually been put to practice way back during the time of the Hanging Gardens of Babylon.

Today, there are several different kinds of hydroponic growing systems, most of them mere variations of the more basic types. Below are four hydroponic growing systems commonly used today.

Water Culture or Aqua Culture

The word hydroponics comes from the Greek word hydros meaning "water" and ponics meaning "method." But research soon dispelled the belief that plants can only grow in either water or soil for scientists discovered that there are other growing media available.

Still, when people hear about hydroponics, most of them would probably think of water culture as the hydroponic growing system used.

On a small scale, water culture method of hydroponic growing system is the simplest form to set up. This system allows plant roots to be totally immersed in nutrient solution. The only trouble with this hydroponic growing system is that you need a large amount of water for supply to each plant, not to mention the need to aerate the solution continuously.

The actual design of this hydroponic growing system is limited only by the imagination of the builder. Just remember the following factors as you build your own water culture system:

* Support the plant above the solution
* Aerate the solution
* Prevent light from reaching the solution (to prevent growth of algae)

The tray or tank to be used as reservoir for the nutrient solution may be made of anything, from concrete or plastic-lined, to asphalt-sealed wood. If you use asphalt to seal the tank, be sure it does not contain creosote or tars. In addition, don't use asphalt that leaves an oil film on the surface of the water.

The tank should be around 6 to 12 inches deep, 2 to 3 feet wide, and as long as in convenient. For plant holders, you can use a plywood top or a piece of 1-inch thick Styrofoam. To place plants, just insert them through holes drilled through the plywood or through the Styrofoam.

Aerate the solution continuously by pumping through a perforated hose or pipe immersed in the solution. For small hydroponic growing systems, an aquarium pump and porous stone will work. Do not bubble the solution too vigorously because excessive movement may damage the tender roots and impair the plant growth.

Aggregate Culture

Another type of hydroponic growing systems is aggregate culture. Aggregate may be made of sand or gravel. This method is often preferred to the water culture method since the aggregate helps to support the roots.

You can use the same type of tank in a water culture system to hold the aggregate in place. The nutrient solution is held in a separate tank and pumped into the aggregate tank to moisten the roots as needed. After the aggregate has been flooded, it is drained to provide aeration. Enough water and nutrients cling to the aggregate and roots to supply the plant until the next flooding.