Hydroponics

[6] In contrast to field cultivation, plants are commonly grown hydroponically in a greenhouse or contained environment on inert media, adapted to the controlled-environment agriculture (CEA) process.

To grow 1 kilogram (2.2 lb) of tomatoes using Hydroponic cultures lead to highest biomass and protein production compared to other growth substrates, of plants cultivated in the same environmental conditions and supplied with equal amounts of nutrients.

[12] The earliest published work on growing terrestrial plants without soil was the 1627 book Sylva Sylvarum or 'A Natural History' by Francis Bacon, printed a year after his death.

By 1842, a list of nine elements believed to be essential for plant growth had been compiled, and the discoveries of German botanists Julius von Sachs and Wilhelm Knop, in the years 1859–1875, resulted in a development of the technique of soilless cultivation.

[13] To quote von Sachs directly: "In the year 1860, I published the results of experiments which demonstrated that land plants are capable of absorbing their nutritive matters out of watery solutions, without the aid of soil, and that it is possible in this way not only to maintain plants alive and growing for a long time, as had long been known, but also to bring about a vigorous increase of their organic substance, and even the production of seed capable of germination.

[16] This approach forced by Dennis Robert Hoagland led to innovative model systems (e.g., green algae Nitella) and standardized nutrient recipes playing an increasingly important role in modern plant physiology.

[17] In 1929, William Frederick Gericke of the University of California at Berkeley began publicly promoting that the principles of solution culture be used for agricultural crop production.

Gericke created a sensation by growing tomato vines twenty-five feet (7.6 metres) high in his backyard in mineral nutrient solutions rather than soil.

[27] As a result of research of Gericke's claims by order of the Director of the California Agricultural Experiment Station of the University of California, Claude Hutchison, Dennis Hoagland and Daniel Arnon wrote a classic 1938 agricultural bulletin, The Water Culture Method for Growing Plants Without Soil, one of the most important works on solution culture ever, which made the claim that hydroponic crop yields were no better than crop yields obtained with good-quality soils.

[31] One of the earliest successes of hydroponics occurred on Wake Island, a rocky atoll in the Pacific Ocean used as a refueling stop for Pan American Airlines.

[32] From 1943 to 1946, Daniel I. Arnon served as a major in the United States Army and used his prior expertise with plant nutrition to feed troops stationed on barren Ponape Island in the western Pacific by growing crops in gravel and nutrient-rich water because there was no arable land available.

Clear containers can also be covered with aluminium foil, butcher paper, black plastic, or other material to eliminate the effects of negative phototropism.

It is much easier to automate than the static solution culture because sampling and adjustments to the temperature, pH, and nutrient concentrations can be made in a large storage tank that has potential to serve thousands of plants.

The main advantage of the NFT system over other forms of hydroponics is that the plant roots are exposed to adequate supplies of water, oxygen, and nutrients.

In situations where this is not possible, the reductions in growth can be eliminated by placing another nutrient feed halfway along the gully and halving the flow rates through each outlet.

[44] A major limitation of hydroponics is the fact that 1 kilogram (2.2 lb) of water can only hold 8 milligrams (0.12 gr) of air, no matter whether aerators are utilized or not.

In its simplest form, a nutrient-and-water solution is manually applied one or more times per day to a container of inert growing media, such as rockwool, perlite, vermiculite, coco fibre, or sand.

Top-fed deep water culture is a technique involving delivering highly oxygenated nutrient solution direct to the root zone of plants.

Notable examples include specialized botanical gardens, cultivation facilities for threatened endemic species, and domestic spaces for advanced horticulture enthusiasts.

Within the center of each rotary hydroponic garden can be a high intensity grow light, designed to simulate sunlight, often with the assistance of a mechanized timer.

[56] Rotary hydroponic systems should be avoided in most circumstances, mainly because of their experimental nature and their high costs for finding, buying, operating, and maintaining them.

Most of the rock wool sold to date is a non-hazardous, non-carcinogenic material, falling under Note Q of the European Union Classification Packaging and Labeling Regulation (CLP).

The manufacturers consider expanded clay to be an ecologically sustainable and re-usable growing medium because of its ability to be cleaned and sterilized, typically by washing in solutions of white vinegar, chlorine bleach, or hydrogen peroxide (H2O2), and rinsing completely.

Coconuts absorb high levels of nutrients throughout their life cycle, so the coir must undergo a maturation process before it becomes a viable growth medium.

This characteristic combined with coconut coir's water retention capacity and resistance to pests and diseases make it an effective growth medium.

If too much water and not enough air surrounds the plants roots, it is possible to gradually lower the medium's water-retention capability by mixing in increasing quantities of perlite.

[69] The formulation of hydroponic solutions is an application of plant nutrition, with nutrient deficiency symptoms mirroring those found in traditional soil based agriculture.

Important differences include: As in conventional agriculture, nutrients should be adjusted to satisfy Liebig's law of the minimum for each specific plant variety.

The free and open source tools HydroBuddy[90] and HydroCal[91] have been created by professional chemists to help any hydroponics grower prepare their own nutrient solutions.

[71] With pest problems reduced and nutrients constantly fed to the roots, productivity in hydroponics is high; however, growers can further increase yield by manipulating a plant's environment by constructing sophisticated growrooms.