Hydroponics comes from the Greek word “hydro,” meaning water, and “ponos,” meaning labor. In other words, hydroponics is gardening without soil. Growing food in a desert can be difficult because of extreme temperatures, low natural precipitation and limited arable soil. Hydroponics can be a viable option to reliably grow fruits, vegetables and herbs, regardless of climate, soil availability or space.
Hydroponic produce can be grown in a home, apartment, greenhouse or office space. The six things needed are light, air, water, nutrients, heat and space.
Hydroponic growing can be done indoors or outdoors. In either setting, plants will need five to six hours of light per day, access to electricity and an area that is level and without excessive wind. Optimal temperature depends on the plant type and variety.
Hydroponic systems can be classified as either water-culture or medium-culture. Water culture systems do not use a medium to support the roots, only the nutrient solution. Medium culture systems use a solid substrate, such as sand, to support the plant root structure. Systems can be either open or closed. In an open system, the nutrient solution flows past the roots, and the solution is not recycled. In a closed system, the surplus nutrient solution is recovered, recharged and recycled through the system.
Water-culture systems use one of the following three methods:
Medium-culture systems use one of the following methods:
The hydroponic medium must provide oxygen, water, nutrients and support for the plant. Medium moisture retention is determined by its particle size, shape and porosity. Popular choices for media are foam, gravel, perlite, rockwool, sand, Hydroton (Fig. 1), coco coir and pumice. Each medium has advantages and limitations, and the choice will reflect availability, cost, quality and type of hydroponic system used.
Rockwool, a mineral fiber derived from basaltic rock, is the most popular hydroponic medium. It provides rapid crop turnaround and minimal risk of crop failure. The open rockwool system also limits diseases in the system.
Fig. 1. Hydroton is a popular medium for hydroponic growing systems. It is made from expanded clay, has a neutral pH and is reusable.
Nutrients are provided to the plant by dissolving fertilizer salts in water. The two options for obtaining nutrient solutions are purchasing a commercial solution or making your own stock solution. An optimum formulation depends on several variables, such as the plant species, stage of plant growth, part of the plant representing the harvest, season during growing and the weather (if outdoors).
Recharging the nutrient solution:
In an open system, the nutrient solution is used only once on crop plants. In a closed system, the nutrient solution is used once, then analyzed for pH and nutrients and adjusted to the proper levels. It must also be sterilized to control the spread of pathogens, and returned to the plants. Common methods for sterilization include heat, ultraviolet radiation and ozone.
Sterilizing hydroponic media:
Medium-culture hydroponic systems are susceptible to pathogenic microorganisms accumulating in the medium with each successive crop. For best results, it is recommended to sterilize the system in between each crop.
Pest and disease management:
Integrated pest management (IPM) is the most effective and environmentally sensitive approach for both commercial and home hydroponic settings. IPM is not a single pest control method but one that is based on frequent monitoring and use of a variety of management techniques that depend on user tolerance to pests and severity of the outbreak. The grower should set action thresholds based on economic threat, monitor and identify pests, practice prevention and control for both effectiveness and risk. The grower must use the most appropriate IPM technique for the situation at hand.
No conclusive evidence is available regarding the nutritional quality of hydroponically grown produce as compared to soil-grown produce. Since hydroponics allows for control over all aspects of growing conditions, it is thought that hydroponically grown crops may eventually be superior to soil-grown crops in nutritional quality.
At University of Nevada, Reno, hydroponically grown strawberries and raspberries were compared to their soil-grown counterparts. Results indicated significantly higher levels of vitamin C, vitamin E and total polyphenolic compounds, but significantly less fructose and glucose, in hydroponically grown strawberries as compared to soil-grown strawberries. Hydroponic raspberries showed significantly lower levels of fructose and sucrose as compared to soil-grown raspberries. These findings may contribute to providing an environmentally sustainable food source in arid or urban growing conditions. More research is needed to determine best methods for hydroponic strawberry and raspberry crop production.
Hydroponics has been adapted to many situations over a relatively short time period. In the future, areas suffering from drought may use desalinated seawater in hydroponic systems and could, therefore, provide food in areas along coasts, in deserts and in developing countries. Astronauts are already enjoying lettuce grown hydroponically on the International Space Station. Research is currently being conducted to investigate other varieties of vegetables for growing hydroponically during space travel that have the potential to feed astronauts on longer missions.
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Integrated Pest Management (IPM) Principles. (2014). Retrieved from United States Environmental Protection Agency.
Resh, H. M., & Howard, M. (2012). Hydroponic Food Production: A Definitive Guidebook for the Advanced Home Gardener and the Commercial Hydroponic Grower. In Santa Bárbara, California EUA (Sixth).
Treftz, C., & Omaye, S. T. (2015). Nutrient Analysis of Soil and Soilless Strawberries and Raspberries Grown in a Greenhouse. Food Nutr. Sci. ,6, 805–815.
Treftz, C., Kratsch, H., and Omaye, S., 2015, Hydroponics: A Brief Guide to Growing Food Without Soil, Extension | University of Nevada, Reno, Fact Sheet FS-15-08
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