Hydroponics, the science of growing plants without soil, is at least as old as the Egyptian pyramids. As a farming tool, it is believed to have started with the hanging gardens in the ancient city of Babylon. The Aztecs created floating gardens by building rafts of rushes and reeds that held crops of vegetables and flowers.
In 1699, John Woodward, a fellow of the Royal Society of England, experimented with growing plants in a liquid medium. Following Woodward's research, European plant physiologists proved that water is absorbed by plant roots, passes through the plant stem system, and escapes into the air through pores in the leaves. They showed that plant roots take up minerals through water.
In 1860, Julius von Sachs, professor of botany at the University of Würzburg, published the first standard formula for a nutrient solution that could be dissolved in water and in which plants could be successfully grown.
In 1936, W.F. Gericke and J.R. Travernetti, from the University of California Berkeley, published an account of the successful cultivation of hydroponic tomatoes. From this study, commercial growers began experimenting with the technique, and researchers and agronomists began working to simplify and perfect the process.
Today, hydroponics is the term used to describe the many varied ways plants can be raised without soil. Plants need air, light, water, and nutrients to grow. Plants do not need soil. They need the nutrients and moisture that can be found in soil. Soil also serves the purpose of anchoring the plant. In a hydroponic system, a growing medium—such as rockwool, perlite, vermiculite, coconut fiber, gravel, sand, clay pellets, etc.—is used to anchor the plant, and a nutrient solution, containing all of the essential elements needed by the plant for its growth and development, is added.
Nutrients are essential to plant growth. Nitrogen (N), phosphorus (P), and potassium (K) are primary macronutrients. The positive effects of the presence of these nutrients at optimum levels and the negative effects of deficient or excess levels can be visually observed in plants.
Nitrogen (N):
- Optimum: Plants are rich green and the protein content increases.
- Deficient: Plants are stunted and light green in color, the lower leaves are yellow, and the stem is slender.
- Excessive: Plants have a very lush foliage with sappy, soft stem and flowering is delayed.
Phosphorus (P):
- Optimum: Phosphorous stimulates root formation and growth, giving the plants a vigorous start. Phosphorous also stimulates flowering and aids in seed formation.
- Deficient: Plants have slower growth and delayed flower and pod development, the leaves are dark green and dull, the root system is poor with little branching, and the stem is slender
- Excessive: Plants have very lush foliage with sappy, soft stems and flowering is delayed.
Potassium (K):
- Optimum: Potassium imparts increased vigor and disease resistance.
- Deficient: Leaves can be mottled or chlorotic, small necrotic spots may appear between veins or near leaf tips and margins, the flowers do not achieve vibrant yellow color, and the stem is slender.
- Excessive: Plants have dark foliage, stiff stems, and leaf branches.1
Hydroponics allows for greater control over the growing process, therefore providing consistent results. Because the soil is replaced with a sterile growing medium, the risks of soil-borne diseases and pests are eliminated and there are no weeds. More plants can be grown in a smaller space. Plants mature faster and produce greater yields. Water and fertilizer are conserved due to their ability to be reused. Hydroponics is a viable option for growing plants in highly populated areas or locations with non-arable land or harsh climates. Hydroponic systems can be found on remote islands, submarines, the International Space Station, Antarctic research stations, and off-shore drilling rigs.
