A hydroponic floating raft uses large beds containing a volume of nutrient solutions. Styrofoam boards or rafts floating on the hydroponic solution support the plants. Floating raft systems are often used to grow plants of short stature like lettuce and basil. The floating raft system in itself is inexpensive and can be built easily. Hydroponics lettuce are one of the most popular salad vegetables grown using the floating raft system. Besides being easy to implement, lettuce also make for a very profitable hydroponic growing experience.
One grow cycle generally takes around 28 to 35 days to complete and floating raft systems can then be reused for other plants. In contrast, field-grown lettuce grow cycles can take about 50 to 60 days from seeding to harvest stages. The varieties of lettuce that can be grown hydroponically are almost the same as those grown terrestrially, including leaf, head and romaine lettuce.
Methods of floating raft culture are sometimes classified as aquaponic culture too, because the ‘raft’ that supports the plants is floating on the nutrient solution. Some growers suggest that placing the ‘raft’ on an elevated wooden plastic-coated margin helps, so that it is not in direct contact with the nutrient solution. This method might help the nutrient solution circulate more evenly without the use of electric pumps, they feel. Otherwise, raft culture is faulted for the stagnant nutrient solutions which are not exposed to air and don’t permit good circulation.
The basic structure of a floating raft system is as follows. An outer box-like structure with an even bottom bed is the center of hydroponic activity. After lining this structure with plastic, it is filled with nutrient solution to a certain level. A Styrofoam board with evenly spaced holes drilled into it is fitted with plastic cups filled with perlite or net cups in which the lettuce saplings are placed. They absorb the hydroponic nutrients solution to grow. If you are not using an elevated raft, be sure to use a pump to re-circulate your solution so that the roots of your lettuce plants manage to absorb the nutrients they need.