Hydroponics and Aeroponics

Von Sachs first demonstrated in 1860 that a plant could be grown to full health in a defined nutrient solution with no soil at all, and later researchers formulated standard recipes for this purpose, notably the Knop solution (1865) and the Arnon and Hoagland solution (1940). William Frederick Goerick coined the term 'hydroponics' in 1940 and also introduced commercial techniques for growing crops this way. In hydroponics, a plant's roots are immersed directly in a nutrient solution, held in place by buoyant pads, while an air pump and air pipe bubble oxygen into the solution and a water-circulation pump keeps nutrients evenly mixed (Figure 12.3) - without this aeration, the submerged roots would be starved of oxygen. Aeroponics, developed by Soifer Hillel and David Durger, takes a different approach: roots are suspended entirely in air inside a mist chamber, and a motor-driven spray rotor periodically sprays the nutrient solution directly over them (Figure 12.4). Both techniques let researchers control exactly which minerals a plant receives, which is how much of what is known about individual mineral functions and deficiency symptoms was originally worked out; commercially, they also let growers raise crops without arable soil. A modern real-world application of the same underlying hydroponic principle is the Floating Treatment Wetland (FTW), a roughly 3,000 sq. ft built structure with four layers - floatable bamboo at the base, a styrofoam layer above it, …