Hydroponics is a method of growing plants using mineral nutrient solutions, in water, without soil. Terrestrial plants may be grown with their roots in the mineral nutrient solution only or in an inert medium, such as perlite, gravel, mineral wool, or coconut husk.

Researchers discovered in the 18th century that plants absorb essential mineral nutrients as inorganic ions in water. In natural conditions, soil acts as a mineral nutrient reservoir but the soil itself is not essential to plant growth. When the mineral nutrients in the soil dissolve in water, plant roots are able to absorb them.

When the required mineral nutrients are introduced into a plant’s water supply artificially, soil is no longer required for the plant to thrive. Almost any terrestrial plant will grow with hydroponics.[citation needed] Hydroponics is also a standard technique in biology research and teaching.

Advantages:

Some of the reasons why hydroponics is being adapted around the world for food production are the following

• No soil is need
• The water stays in the system and can be reused – thus, lower water cost
• It is possible to control the nutrition levels in their entirety – thus, lower nutrition costs
• No nutrition pollution is released into the environment because of the controlled system
• Stable and high yield
• Pests and diseases are easier to get rid of than in soil because of the container’s mobility

Today, hydroponics is an established branch of agronomy. Progress has been rapid, and results obtained in various countries have proved it to be thoroughly practical and to have very definite advantages over conventional methods of horticulture. The two chief merits of the soil-less cultivation of plants are, first, hydroponics produces much higher crop yields, and, second, hydroponics can be used in places where in-ground agriculture or gardening are not possible.

Techniques:

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 main types of solution cultures are static solution culture, continuous-flow solution culture and aeroponics. The medium culture method has a solid medium for the roots and is named for the type of medium, e.g., sand culture, gravel culture, or rockwool culture.

There are two main variations for each medium sub-irrigation and top irrigation. For all techniques, most hydroponic reservoirs are now built of plastic, but other materials have been used including concrete, glass, metal, vegetable solids, and wood. The containers should exclude light to prevent algae growth in the nutrient solution.