Hydroponics means "water working" in Latin. It is the practice of delivering plant nutrition through enriched, highly oxygenated water instead of through a growing medium such as soil. The main advantages of doing this are to avoid soil-borne pathogens and to give the plant more energy toward producing fruit by putting less into growing deep roots.
Basic plant needs
So far, science has identified at least 12 elements that plants use for growth. Of these, three are the most important, in order they are nitrogen, phosphorus and potassium. Calcium, Magnesium, Sulphur, Iron, Manganese, Zinc, Boron, Copper and Molybdenum all play a role, in much lesser amounts.
Types of hydroponics
Roots need water, oxygen and essential nutrients to survive and thrive. If the nutrient fluid contains enough oxygen, roots can bathe continuously in it. Some hydroponics assemblies keep the water flowing in a continuous circuit, recharging its oxygen content in each pass, but since completely-drenched roots without enough air can drown and rot, most hydroponics setups flood the roots at specific time variables, then drain completely to allow for oxygenation in between feedings.
Aeroponics is a variation of the basic hydroponic archetype. These facilities suspend the plants in the air. For this to work properly, the atmosphere must have 100% humidity to prevent evaporation, and the nutrient solution has to be applied to the roots in a fine spray. Proponents claim that the yield of aeroponics systems is even better than that of other hydroponics configurations.
Aquaponics takes advantage of the natural symbiosis between animals and plants in order to produce both crops and protein. Fish and their uneaten food produce waste, which is toxic for them, but excellent fertilizer for plants. Water from the tank is pumped to the roots. In the process, as the plants take up the nutritious nitrates, they clean the water for the fish, which is then splashed back into the tank. The splashing oxygenates the water. The nitrogen and other ingredients in fish waste is sufficient to fully fertilize the plants. The only input thus needed in the whole system is fish food. The environmental hazards from farmed fish are thus eliminated, or greatly reduced, even as the system produces a vegetable crop.
Expense and labor are the greatest barriers to the more wide-spread use of hydroponics commercially. Dirt is as cheap as, well, dirt, but hydroponics requires specialized equipment. In soil, nutrients and air are available to the plant all the time, but in hydroponics, timing is everything to give the plants what they need when they need it. Composted manure, leaves and green vegetation are easy, abundant and cheap inputs to soil nutrition, but hydroponics requires balanced nutrients in solution. For the most part, hydroponic cultivation works for high-value crops that are highly susceptible to soil-borne pests. Viable commercial aquaponics facilities are reportedly running in the black, mostly in warmer climates where plants can grow year-round.