Hydroponic Systems: Active vs. Passive

A hydroponic system is essentially a method of growing plants without soil. Hydroponics has been around for centuries, though scientists didn’t begin to seriously study hydroponics until around the 1950s. Since then, it has become a successful and important form of plant and crop production, especially for countries not typically suitable for crop growth.

Types of Hydroponic Systems

Generally, there are two ways that hydroponic systems are characterized. The first is either as an active or a passive system, which is a reference to the type of nutrient system used. Active systems tend to bring healthier and faster growth, while passive systems are often a little easier to set up and maintain. The other way to characterize them is by recovery or non-recovery, which refers to whether or not nutrients are recovered after use.

Passive Systems

Passive systems rely on capillary or wick systems to deliver nutrients to the plant’s roots. What this means is that nutrients, which are in a fluid solution, are drawn up and absorbed by the growing medium, a wick, or some other device, and passed on through contact to the roots. Materials such as candle wick or lantern wick can be used for this capillary action.

While the passive system is often one of the easiest to set up and maintain, due to the fact that it has no pumps or moving parts, one of its greatest drawbacks is that it tends to leave the plant’s roots continuously wet. This constant wetness prohibits the best flow of oxygen, which is required for the best plant growth. Also, passive systems are generally non-recovery systems, as there is no way to recover nutrients that are not directly absorbed by the roots. Therefore it is not the recommended way to set up a hydroponics system.

Active Systems

Active systems rely on pumps and other mechanical devices to actively move the solution to the roots. As a result, this often makes it easier to reuse nutrients, meaning that active systems are also usually recovery systems. Also, because the flow of nutrients can be directly controlled, it is easier to manipulate the nutrient solution around the roots to allow the best absorption of oxygen, which in turn promotes stronger, healthier growth.

The ebb and flow system is a popular form of active, recovery hydroponics. The way it works is simple; the nutrient solution sits in a reservoir below the tray holding the plants. A pump is submerged into the solution which, when turned on, pumps the nutrients up to the plant tray and floods the roots for feeding. After running the pump for about 20 or 30 minutes, it is turned off and the excess solution is allowed to drain slowly back down into the reservoir for recovery. Not only does this supply the plant with all the nutrients it needs, but the removal of nutrients after flooding will pull fresh oxygen down to the roots, further promoting proper plant growth.

The ebb and flow system, while not quite as simple as a wick system, is still easy to set up, is very affordable for even the casual hydroponics gardener, and produces very effective results.