Hydroponics is the process of growing food with nutrient-rich water instead of soil.
NASA has investigated hydroponics as a means of producing the crops required to meet the life support needs of astronauts in long-term space exploration missions through a ‘Biomass Production Facility’ and scientists have even exploited hydroponics in nanotechnology by 'growing' metal nanoparticles in living plants!
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Although hydroponics is defined as growing plants without soil, in reality many systems use an inert, sterilised material or substrate to support the plants and the inorganic ions and minerals essential for healthy plant growth and development are provided by nutrient solutions. However, some systems, such as the nutrient film technique (NFT), which is widely used commercially in the UK, only use supporting media during propagation, and so are truly hydroponic.
Green energy, such as wind and solar, can heat greenhouses during off-seasons, so produce can be grown anywhere year-round increasing number of farmers markets and the farm-to-table movement as evidence of hydroponics' bright future.
"Now you can grow the produce for the same price as it's being shipped from California, but the difference it is it ends up being healthier, tasting better and being more nutritious, "It's not been picked and shipped for 3,000 miles. It's local."
With hydroponics, the space constraint and soil contamination found in urban areas is no longer a deterrent for growing local. A person can grow 40 plants within a space of two square feet.
Ask people the question ‘what do plants need to grow?’ and their replies will almost certainly include soil and water. Yet hydroponics – the technology of growing plants without soil – is widely used around the globe for growing food crops. While the term often conjures up images associated with the illegal growing of certain plant species, the role of hydroponics in food production is less well known despite the fact that many fruits and vegetables on display in supermarkets are grown hydroponically. And as we move into an era in which food supply will become a key global challenge, hydroponic production has the potential to play a bigger role in meeting the increasing demand for food.
We insist on living on parts of the earth covered by desert, rock, or ice. Because those places don’t produce their own food, feeding the people who live there requires a global network of food production and transport. For desert nations such as the Gulf States, where as much as 90% of food is imported, this is a precarious situation, and can easily lead to shortages. When that happens, and food prices skyrocket like they did between 2005 and 2008, it can lead to unrest.
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Redeploying a technology designed for medical applications, Japanese researcher Yuichi Mori at Waseda University is using a plastic "hydrogel" membrane resembling Saran Wrap to grow plants on a transparent, soil-free film. The technique uses one-tenth of the water and a fraction of the fertilizer to grow the same produce as conventional agriculture. The plants are generally free of pathogens, pesticides, and pollutants such as oil or heavy metals because the membrane is selective: Water drawn up by the plant’s roots pass through it, but other compounds are left behind.
There are many advantages to hydroponic production, especially faster growing times, which enables multiple crops per season, higher yields and year-round production with reduced risk of crop failure due to adverse weather, pests or disease. Furthermore, the plants are grown much more closely together than in soil, often by vertical-training or in columns, leading to space savings and higher yields per unit of land; it has been estimated that productivity through hydroponic cultivation is increased four-fold for cucumber, 10-fold for tomatoes and three-fold for lettuce. These controlled environments lead to a more consistent quality of produce and the earlier detection and correction of nutritional deficiencies than in conventional soil-based horticulture.
The most popular crops grown hydroponically are tomatoes, cucumbers and sweet peppers; others include melons, lettuce, strawberries, herbs, aubergine, chilies, and ornamental plants and flowers. In 2009, the UK produced 87,000t of tomatoes most using the NFT technique in greenhouses covering ca. 200 ha of land and employing almost 2500 people. Approximately 3520 ha of land would be required to cultivate the equivalent quantity in soil.Despite the advantages of hydroponic horticulture, however, the industry faces a number of economic and physical challenges. The past decade has seen a 10-fold drop in tomato production in the UK, with only 20% of the tomatoes sold in the UK today being grown domestically. A staggering 400,000t of fresh tomatoes are imported from countries such as Spain, Canary Islands, Holland, Morocco, Poland, Italy, Belgium and Israel. In the early 1990s, Spanish growers adopted 800 ha of land for hydroponic production and a decade later, this had risen to 4000 ha. The main reason is the cost of production; the Mediterranean climate is milder, especially in winter, so less heating is required than in the UK, where expensive climate control and supplementary lighting is needed.
The world’s population will grow to an estimated 8bn people by 2025 and 9bn by 2050. To satisfy the anticipated demand, 50% more food will need to be produced on the same land area. From a commercial perspective, hydroponic technologies have the potential to help meet this increased demand, particularly in those regions of the world that have limited arable land such as Africa, Asia and parts of Australasia and the US.
Future developments in hydroponic techniques are likely to concentrate on energy and water usage; recirculating systems can be very water-efficient, re-using up to 90% of the water. Nutrient management in agricultural production is increasingly important and is more effective in hydroponic than soil-based production, so preserving scarce mineral resources – particularly phosphate. Accessible sources of phosphate are close to exhaustion, with an estimated 100 years of supply remaining, so hydroponics could play a role in preventing the overuse of phosphate and the recovery and recycling of unused phosphate nutrients.
For the home/DIY market, hydroponics is likely to remain a niche part of the broader gardening and 'grow your own' market. Nonetheless, there are opportunities for business growth, although the longer-term prospects are inextricably linked to the price and availability of the minerals used in the nutrient solutions
The term hydroponics incorporates a number of related techniques that can be split into two broad categories.
Media-based systems use materials such as rockwool, coir fibre, perlite or clay pebbles to support the growing plants. The nutrient solutions are delivered by drip feeding or by ebb and flow, in which the plants are flooded with a nutrient solution at pre-determined intervals, pulling oxygen from the atmosphere to the root zone. The solution is then drained back into a header tank and re-circulated.
Non-media techniques include the Nutrient Film Technique (NFT) in which plants are grown in an 'open root system' with re-circulating nutrient solutions. In so-called deep water culture, the roots are permanently submerged in a nutrient solution which is aerated to maintain adequate levels of dissolved oxygen and prevent stagnation. This method is more popular with the DIY market due to its ease of use. In aeroponics the roots are suspended in an environmental chamber and sprayed with nutrient solution.
The common feature of all hydroponic systems is the requirement for aqueous nutrient solutions, which provide the plants with all the elements they require. The macro-elements, N, P, K, Ca, Mg and S, are provided in high concentrations, usually as mineral salts – normally nitrates, sulfates, phosphates. The microelements, Fe, Cu, Zn, B, Mo and Mn, are typically supplied as complexes chelated with EDTA at much lower concentrations. Traditionally, nutrients are produced as two stock solutions, known in the industry as 'A' and 'B'. The 'A' solution contains the calcium and magnesium salts and the 'B' solution the phosphate, sulfate, potassium and microelements. This avoids formation of unwanted calcium phosphate and sulfate precipitates that reduce the bioavailability of these elements and block the physical infrastructure. The nature of the nutrient solution is tailored for the specific application, such as species of plant or local conditions such as water hardness.