The term "hydroponics" comes from the Greek word "hydro," which means water, and "ponos," which means labor. It means cultivating plants in a nutrient-rich water, rather than soil. The plants can grow in the hydroponic water solution by itself or with rocks, perlite or gravel added to the solution. Soil acts as a reservoir for the plants and is not essential for the plant's growth. There are two types of hydroponic planting techniques. The earliest written recordings of hydroponics being used were in 1627.
In the 19th century, scientists found plants could receive nutrients from water without soil. In 1627, Sir Francis Bacon wrote a book called Silva Silvarum. In 1966, John Woodward published his book on experiments with spearmint. He found plants grew better in less pure water than distilled water. Many researchers wrote books on hydroponics. A water-nutrient solution called the Hoagland Solution is still used today. The term "hydroponics" does not include other types of soilless culture such as sand culture and gravel culture.
When nutrients are introduced to plants in the water supply, there is no need for soil. Almost any plant will survive in hydroponics. This method is used a lot in teaching students about hydroponics. The two main types of hydroponics are solution culture and medium culture. Solution culture does not use a solid medium for the roots--just the nutrient solution. The three types of solutions are static solution, continuous flow solution and aeroponics. The medium culture method has a solid medium for the roots and uses sand, gravel or rockwool. Most hydroponic reservoirs are now built of plastic, but other materials have been used.
Advantages & Disadvantages
Advantages of hydroponics abound: no soil is needed; water can be reused, because it stays in the hydroponics system; you can control the level of nutrients easier; and no pollution is added to the environment. The yield of fruit and plants are also higher than with regular farming. Pests are easier to control and plants can be produced out of season with hydroponics.
There are some disadvantages to hydroponics, as well: the presence of high humidity can stimulate salmonella growth and verticillium wilt can be caused by high moisture levels.
Plants can be grown hydroponically at home in mason jars, plastic buckets, tubs or tanks using a fish tank pump for irrigation. Containers should be covered with aluminum foil, black plastic or other material to exclude light. Nutrient levels should be checked and changed if needed on a weekly basis. As plants increase in size, the grower should thin plants out and add excess plants to other containers.
Types of Solutions
In static solutions, plants are grown in containers of nutrient solution with a steady air flow. Continuous flow solution is where the nutrient solution constantly flows past the roots. Aeroponics is a system where roots are continuously kept in an environment saturated with fine drops of nutrient solution. Passive hydroponics, or semi-hydroponics, is a method where plants are grown in a medium that transports water and fertilizer to the roots by capillary action, producing a constant supply of water to the roots from a separate reservoir.