Three factors are needed for plant growth: air, water and nutrients. Soil is generally used and provides the nutrients, holding both the water and the air. More importantly, soil provides the foundation to keep the plant upright and where you want it. Soil is not required or needed if you can provide all of these factors another way.
Hydroponics, nutrient-solution culture, water culture, soilless culture, gravel culture, nutri-culture, whatever you call it, has been around since the 16th century. Some historians even claim that the Babylonian Gardens were hydroponic. Serious pioneering began in the 19th century and is now used around the world for growing plants without soil. Growing plants without soil is the real definition of hydroponics.
Hydroponics require the grower to submerge or douse the plant root system with nutrient-rich water. Submersing the roots requires oxygen-rich water (a bubbler or aerator); dousing requires a short period without water to provide the air. Different methods, same principle; provide air, water and nutrients. Any method also requires some kind of physical support for the plant (gravel, plastic pellets, wire mesh, etc.) and, of course, sufficient light.
Advantages of a soilless system include having no soil structure or texture to maintain, no weeds, no raking, no soil-borne pathogens, no need to water, no moles, no cutworms, and the biggie: specific nutrients can be made available to specific plants immediately only when, and if, they need it. The latter is what really supports the claims of bigger plants’ increased yield and higher nutritional value.
Disadvantages of using a soilless system include having to maintain the balance of nutrients in the solution, pH monitoring, pump maintenance, and a high initial cost. These disadvantages are being overcome with automation, human ingenuity and commercialization.
So why the hype? Hydroponic production requires less labor than conventional methods. There is no soil prep, no weeding, reduced water expense, and centrally controlled feeding. Areas with poor or no soil can be utilized (arid landscapes, rooftops, vertical walls and even in space). With enough light, plants per square foot increase and vertical space is utilized.
For the home gardener, starting seeds with a wicking system is easier, and for gardeners with no place to grow, hydroponics is an alternative to finding a good south window or playing with the dirt. Small window sill systems (those containing their own light source, aerators and timers) carry hours of interest, deliver fresh produce, and provide a great learning tool for kids and adults.
I purchased an AeroGarden self-contained unit some weeks ago. I fuss and watch over it daily, and my wife is anxious for great volumes of herbs. It reinforces my friends’ claim that I really need to get a life. Let them eat basil.