Hydroponics
This uses a system where the roots of the plants are contained in a chamber which is sprayed continuously or discontinuously with a fine mist of water containing nutrients. The roots of the plant hang in the air and the advantage of this system is that the roots have good access to oxygen. This system was invented in 1983 by Richard Spooner and has become a successful way of growing a wide range of crops including seed potato production, tomato production, leaf crops, and small salad leaves. Other advantages of aeroponics are that a much wider range of plants can be grown with this system, (some plants do not like to have their roots in water continuously) plants grow with only one quarter of the nutrients needed in normal hydroponics and NASA has an interest in this system because managing a spray is easier than handling liquids in zero gravity. Finally, plants grown by this method can be transferred to soil or another growing medium without suffering from a slowing of growth while they adjust to the new conditions. The main disadvantage is that this system is more costly to build and maintain than the normal hydroponic systems.