Hydroponics is a farming method of growing plants inside an enclosed structure without soil, but in a selected growing medium where the lighting, temperature, and nutrients are closely regulated.
There are two basic forms of hydroponics: soil-less mediums, such as clay, sand, rock wool, perlite, and vermiculite, and true hydroponics, which use only a water-based solution of required plant nutrients. The most commonly grown hydroponic crops in the United States are lettuce, tomatoes, peppers, cucumbers, herbs, and flowers.
Soil research experts discovered that soil acts as a stabilizer, keeping the plant in a vertical growing position, and as a source of minerals for the plant. Experiments with flowers and vegetables suggest that if a plant's structure is given artificial support, its root system can absorb all of the nutrients it needs directly from a water-based solution without the need for soil.
Modern plant researchers recognize nine basic elements needed for adequate plant growth and production: nitrogen (N), phosphorous (P), sulfur (S), potassium (K), calcium (Ca), magnesium (Mg), hydrogen (H), oxygen (O), and carbon (C). Seven additional trace elements, including iron (Fe), chlorine (Cl), manganese (Mn), boron (B), zinc (Zn), copper (Cu), and molybdenum (Mo), promote healthy growth. Hydroponic growing solutions need to supply all of these nutrients for healthy and productive growth, regardless of the type of delivery system used.
The earliest record of hydroponic gardening was by Sir Francis Bacon in 1627. By the mid-1800s, plant researchers started outlining a list of nutrients that plants require for growth and reproduction. The University of California's William Gericke promoted the use of a water-based solution for soil-less crop production in the 1920s. Gericke's solution was based on the first standardized formula for a nutrient solution, which included the nine basic elements for growth, created by Julius von Sachs, Professor of Botany at the University of Wurzburg in 1860. According to secondary sources, Gericke is reported to have grown tomato plants that were about 20 feet high in his backyard mineral solution tanks.
The National Aeronautics and Space Administration's (NASA) reports show that the military produced hydroponics crops at multiple overseas bases during World War II in order to provide fresh produce to the American troops. On the islands of the South Pacific Ocean, such as Wake, hydroponic farming was highly successful.
The early years of hydroponics created a heated debate as to what exactly the term "hydroponics" should include. It was unclear if it was a term for plants grown in only nutrient solutions or if it could include plants grown in soil-less mediums, such as sand, gravel, or air. Eventually "soil-less culture," or "hydroponics," was coined for a growing method that used a substrate other than soil. A specific type of hydroponics called "aquaculture" refers to the growth of water plants or fish and "aeroponics" refers to plant growth in air.
Crops can be grown out of season, as current hydroponic farming is done within the confines of environmentally balanced, covered structures, such as greenhouses, garages, basements, and apartments. Commercial hydroponic farming in the United States is done predominately within greenhouses.
Hydroponic gardening may be used in dense urban areas, deserts, mountains, and ice-covered regions.
The interest in the use of hydroponics stems from its high-crop production rate, using only small growing areas, and its flexibility in geographical regions hostile to traditional farming methods.
Hydroponic produce may be subject to insect damage and it requires insect control measures. Insect pest control work shows promise in natural based pest-management techniques against insects such as lady bugs and praying mantis, as compared to the use of chemical sprays or powders.
Using a greenhouse/an indoor setting limits access to the crops by rodents.
No herbicides are needed, as the plants are not exposed to harmful organisms found in soil. Although hydroponic crops are grown without herbicides, the U.S. Food and Drug Administration (FDA) does not consider hydroponic produce to be organic, since it is grown in an artificially-created nutrient environment.
Hydroponic crops can be harvested and consumed locally with decreased manufacturing and transport costs. However, labor costs for hydroponic farming are similar to traditional farming labor costs due to the need for testing of the irrigating solution and frequent monitoring of the nutrient delivery systems.
Unlike the produce grown in nutrient-depleted soil found in many areas of the world, hydroponic produce may contain more complete nutrition than the equivalent soil-grown produce, as all needed nutrients can be delivered to the developing plant through the growing solution.
Fresh, pure rainwater or municipal water must be used in hydroponic gardening to prevent water-borne organisms from contaminating the produce.
A wide array of hydroponic farming studies is being conducted. For instance, NASA is studying the technique for deep-space food production, while Disney World's© Land Pavilion serves hydroponic produce in their restaurants. Other organizations, including the McCurdo Station research facility in Antarctica and large commercial greenhouses in Arizona and Florida, are also studying hydroponic farming. Several countries, such as Israel, Ecuador, Peru, and Nicaragua, along with multiple Persian Gulf countries and small inner-city Philadelphia neighborhoods are growing hydroponic produce. Hydroponic gardens can be as simple as a kitchen countertop container or as high-tech as multi-acre commercial ventures.
Because there is growing concern that conventional farming practices may not produce enough crops for the increasing human population, many nations, world health organizations, and farming ventures are recognizing the potential of hydroponic farming.
General: There are two basic forms of hydroponics: soil-less mediums, such as clay, sand, rock wool, perlite, and vermiculite; and true hydroponics, which use only a water-based solution of plant nutrients.
All water-based hydroponic solutions, regardless of how the solution is supplied to the plant, need to provide nitrogen (N), phosphorous (P), sulfur (S), potassium (K), calcium (Ca), magnesium (Mg), hydrogen (H), oxygen (O), and carbon (C), as well as the trace elements of iron (Fe), chlorine (Cl), manganese (Mn), boron (B), zinc (Zn), copper (Cu), and molybdenum (Mo). Calculation of the proper amounts of nutrients is determined by the type of plant being grown and the stage of maturity of that plant. This can be a complex process. Recently, pre-mixed nutrient solutions have been brought to the market for consumer purchase, but are too costly for large farming enterprises.
The pH level of the nutrient solution must be maintained within a narrow range as determined by the specific type of plant. This pH level varies depending on the needs of the plant's growth. Plants, such as tomatoes, require a pH between 5.5 and 6.5, while plants, such as beans, require a pH of between 6.0 and 6.5. If the pH of the solution is not at the proper level for the plant, the plant will lose its ability to take up the nutrients in the solution and be unable to grow. Hydroponic farmers test the pH of their nutrient solutions frequently and adjust the pH balance accordingly.
Access to clean fresh water (municipal or rainwater) and electricity are two essential requirements for hydroponic gardening.
In some geographical locations, artificial heat, humidity, or air conditioning may be needed. In Arizona, hydroponic farms must supply humidity and air conditioning to the plants to keep them alive. Similarly, in extremely cold climates, additional heat may be required to maintain the plant's viability. Temperature regulation is carefully monitored during the growth of the plant and must remain constant at 65-75 degrees Fahrenheit during the day, with a 5-10 degree decrease at night.
Adequate light is a major factor for a successful crop yield. Plants require up to 16 hours of light daily.
Some commercial tomato farms in northern climates, such as in the Netherlands, grow produce year-round inside a strictly climate-controlled greenhouse environment, adding in supplemental levels of carbon dioxide to encourage higher crop yield, without sacrificing the quality of the produce.
Home hobbyists may set up their units in a room, basement, or garage. Many move their units to an outside site, such as a patio or balcony, during the summer months.
Initial start-up costs of the equipment and solutions are a determining factor in production costs. Electricity, water, pest management products, and nutrient solutions are ongoing costs.
Examples of hydroponic solution delivery systems currently used in modern hydroponic farming are the wick system, the water culture system, the drain and flow system, the drain system, the nutrient film system, and the aeroponics system. These various hydroponic delivery methods are chosen depending on the specific needs of the type of plant being grown.
The wick system: The wick system is a passive system where the nutrient solution is drawn up to the plant from a reservoir by a wicking material. The most common wicking mediums are perlite, vermiculite, Pro-Mix©, and coconut fiber. This is the simplest form of hydroponics and is used frequently in educational curriculums. The system's drawback is that it uses large amounts of nutrient solution.
The water culture system: The water culture is an active system where the plants float directly above the nutrient reservoir while an air pump adds oxygen to the solution for the plant's roots. This system is used frequently in lettuce production. It does not work as effectively with large plants or plants that will be maintained for long periods of time.
The flood and drain (ebb and flow) system: The flood and drain system is an active system where the solution is pumped up to the grow tray and the medium is flooded by the nutrients. Excess solution is returned to the reservoir for reuse. An electric timer is used to set the frequency of the flooding of the plant tray medium. The growth medium used in this system can be rock wool, Grow Rocks™, gravel, or perlite. Care must be taken not to allow the roots to dry out, as the growing medium does not retain water.
The drip system: The drip system is the most widely-used system throughout the world. In this approach, a timer controls a pump that allows the growing solution to be dripped onto the base of each plant. Excess nutrient solution can be recaptured if desired. Care must be taken to determine that every plant is given the same amount of solution and that as the pH level of the solution in the reservoir remains at the desired level.
The nutrient film technique system: The nutrient film technique is a complex system of hydroponics requiring high-tech monitoring of nutrient delivery. In this approach, a constant flow of nutrient solution is pumped over the bare roots of the plants. There is no growing medium; the plant is supported within a plastic or mesh basket. Frequent management of the system is needed to keep it working properly. Commercial farming ventures use this technique.
The aeroponics system: The aeroponics system is the most sophisticated form of hydroponic gardening. The plants are suspended in the air by a special rack, and the nutrient solution is sprayed onto the exposed roots. Mistings are done every few minutes. This system is currently being researched for zero-gravity space travel by NASA.
Potential benefits of hydroponic farming: According to Dr. Howard Resh, who has studied hydroponics since the early 1970s and is involved with the Hydroponic Services, Anguilla, British West Indies, this farming method may have the ability to grow more produce per plant and per area unit than regular soil farming. In tomato farming, for example, the average yield of hydroponic tomatoes per acre is eighteen times more than what is produced on soil acreage. Hydroponics uses as little as 1/10th the amount of water used in traditional farming. Less fertilizer is required per plant than what would be needed for the equivalent traditional farm plant.
The growing season is extended and because the plants are generally grown in confined structures where temperature and humidity are regulated, they may be produced in areas of extreme or variable climates.
Plants are not exposed to soil diseases. Nutritional content of the produce may be more complete than crops grown in poor-quality soil.
Commercial growers are now picking 4,000-5,000 pounds of tomatoes every week. Additionally, lettuce is maturing in less than four weeks, and farmers are picking up to 3,000 heads per week in only 20,000 square feet of greenhouse space.
Potential disadvantages of hydroponic farming: Start-up costs for a hydroponic farming facility are generally equivalent to that of a traditional farming facility. As a result, current farm landowners may be unwilling to convert to hydroponic systems.
Hydroponics requires higher energy costs and equipment expense than traditional farming methods. Labor costs are similar to traditional farming as hydroponic systems require frequent overseeing of the nutrient delivery system and pH levels. Technical understanding of the plant's requirements for specific nutrients during specific growth phases requires learning and practice. In the event of an extended power outage, potential catastrophic loss of entire crops may occur with any of the active delivery systems.
Quality and quantity of fresh produce has long been established as necessary for optimal human health. Access to quality farm produce is limited or unavailable in many geographical regions of the world.
Hydroponic farming provides a clean, efficient method whereby urban and rural populations can supplement their diets with fresh fruits and vegetables. Studies suggest that the nutritional composition of hydroponic crops may be equal to or possibly even superior to traditionally grown produce.
In 2000, the government of Ecuador, aware that its poor population had limited protein intake and "almost no fruit or vegetables" in their daily diets, worked with the Food and Agriculture Organization of the United Nations (FAO) to provide a simplified hydroponic project to eight locations within the country. Its goal was to have the families be able to feed themselves and, if possible, provide the families with a small income. Using local recycled materials and rainwater, school children were recruited under the supervision of designated trained monitors. The positive impact on the communities showed a decline in diseases of the local children and an increase in the consumption of vitamins A, B2, C, D, and E, as well as iron, calcium, phosphorus, iodine, and manganese. These communities expressed an interest in expanding their production for resale.
Concern over the health implications of potential contamination of hydroponic nutrient solutions has been voiced by some consumer groups. No specific U.S. government agency regulates or certifies hydroponic farms. The U.S. Food and Drug Administration (FDA) does investigate in the event of any public health issues, as it does with traditional soil-based farming.
The 2008 E. coli contamination brought hydroponics under scrutiny when hydroponically grown tomatoes and peppers were initially implicated in the outbreak. The FDA eventually cleared the commercial growers of that outbreak; however, it highlighted the need for strict and detailed management procedures for the growing solutions and their delivery systems.
Hydroponic farming requires as little as 1/10th the amount of water used in traditional farming. Less fertilizer is required per plant than what would be needed for the equivalent traditional farm plant.
Hydroponic farming also allows the growing season to be extended and, because the plants are generally grown in confined structures where temperature and humidity are regulated, they may be produced in areas of extreme or variable climates.
FUTURE RESEARCH OR APPLICATIONS
Experimental methods are being researched for growing hydroponic melons, grapes, cotton, pumpkins, grapefruit, and corn, which have not been successful crops using current hydroponic technology.
New research into vertical hydroponic growth systems is being conducted to possibly increase the use of available acreage.
Natural forms of pest management are being researched in Antarctica and at the Land Pavilion at Disney World© to potentially decrease the reliance on toxic chemicals.
In April 2008, United Nations (UN) Secretary-General Ban Ki-moon issued a warning that price increases in food are being felt across the world, as far away as Malaysia. The UN's position is that hydroponics could provide a source of plentiful, healthy food production as the world population grows.
It has been suggested that countries around the world that have been unable to adequately grow fresh produce may use hydroponic farming as a potential way to increase production despite unfavorable traditional growing environments.
Proponents contend that hydroponic farming may be beneficial for small businesses and families because they could sell their extra produce.
Inner-city areas in the United States, such as New Kensington and Fishtown in northeastern Philadelphia, have successfully converted vacant lots into productive hydroponic green areas, providing fresh produce to neighborhood residents. It is becoming a model for other inner-city low-income areas.
Ohio State University has devised an interactive calculator Web site for the commercial farmer and hobbyist to determine plant yield estimates and growing parameters and thus the cost return of specific crops.
This information has been edited and peer-reviewed by contributors to the Natural Standard Research Collaboration (www.naturalstandard.com).
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