Given that, practically speaking, the roots are growing in air; they always have sufficient oxygen available and large yields become possible. The biggest disadvantages off aeroponic systems are the relatively high initial investment costs and the systems’ proneness to malfunction. Leaving a thin layer of water on the bottom of the misting room will ensure that plants don’t go without water if there should be a system failure.
Ebb and flood systems
In an ebb and flood system, the plants are placed in a box that is periodically pumped full of nutrient solution. The substrate soaks up the nutrient solution, which is then pumped away. By filling the box with nutrient solution the old air is pushed out as the solution is pumped away and fresh air flows into the medium.
In order to prevent oxygen shortages from occurring around the roots, the medium must not be saturated for too long with water and it must contain sufficient air when the nutrient solution has drained away. One guideline for this is to ensure that the process of pumping full and then emptying should take no longer than 30 minutes.
The recommended frequency for flooding depends on the substrate that is being used and each plant’s root volume. Clay pebbles retain little water and must be flooded more often than a system with rock wool, for example, which will hold more water.
Drip systems
Drip systems are perhaps the most common type of hydroponics systems in the world, owing to their simplicity. A clock controls a pump in the nutrient tank. When the clock switches on the pump and a small drip mechanism drips a nutrient solution over the base of each plant. The excess nutrient solution is caught in the nutrient reservoir for subsequent reuse, or drained away.