Introduction to Hydroponics

This informative in providing articles written by Dr. Haward Resh as well as anyone else who wishes to contribute. If you have something to share with us, please submit it at the e-mail address on the website. Our objective is to provide articles monthly.


We shall also keep you up on new products for hobby hydroponics. Within several months we expect to introduce a new hobby hydroponic kitchen unit. It will be available for purchase through this website. We shall announce conference dates and places that may be of interest to our readers. Although materials presented here may be applicable to commercial and hobby growers, the emphasis is toward hobbyists.


Hydroponics vs. Soilless Culture:

There are really two forms of hydroponics, soilless culture and true hydroponics. Because we include in hydroponic systems those that use substrates, we must make it clear that while correctly they are termed “soilless culture,” principles of hydroponics apply. Therefore, we generally speak of hydroponics to include not only the true hydroponics (water culture) but all systems using substrates (soilless culture). Pure hydroponics by definition means “water working.” The word comes from the Greek words hydro (“water”) and ponos (“labor”) – literally “water working.” These include water (solution) culture, nutrient film technique (NFT), floating or raft culture, and aeroponics. Aeroponics is a form of hydroponics whereby the nutrient solution is provided to bare roots suspended in a growing chamber or channel (Photo 1).



The solution is sprayed from below the roots in a fine mist. These aeroponic systems in general are more complex than soilless methods. When we design and set up hobby hydroponic systems we should lean toward simplicity to avoid technical challenges within the system. Such simple systems include soilless and some water culture systems.


Application of Hydroponics:

Hydroponics is a science that can be applied at many levels of simplicity or complexity. Your potted houseplants, such as foliage plants and flowering plants, are in a soilless culture system. They use a “peatlite” mixture of peat, perlite and/or vermiculite for their medium. These plants are grown in greenhouses using a nutrient solution fed by drip or ebb & flow irrigation systems. With ebb & flow the nutrient solution is periodically flooded at the base of the potted plants followed by complete drainage. When you purchase potted houseplants you will need to feed them plant food frequently in order to keep them thriving. After they have left the greenhouse or garden center they will no longer receive the food normally provided to them by a hydroponic system. The point is that the growing of individual plants in a pot with a soilless substrate is hydroponics in a fairly simple form. This is in effect hobby hydroponics.


Hydroponics in its simplest form may be applied to low income areas of the World. I have seen this in Peru. No equipment requiring electricity is needed provided the people are willing to spend a little time every day to irrigate their plants manually. Mr. Alfredo Delfin and staff at the Universidad Nacional Agraria La Molina have assisted low-income families to produce fresh vegetables using basic soilless and raft culture systems.



These projects have been put together as roof-top gardens (Photo 2) on public buildings as well as in people’s backyards. Discarded plastic containers and tires were filled with a soilless substrate of rice hulls and ground coconut husks (coco coir) (Photos 3 & 4).




These are watered several times a day with a nutrient solution prepared from a formulation developed by the University. Such basic systems of hydroponics exemplify how the science may be applied in a simple manner.




Of course, we can get highly technical with hydroponics as we see in greenhouse operations (Photos 5 & 6) and its use under zero gravity on the space station (Photos 7 & 8).




This versatility of hydroponics makes it a very fascinating and rewarding hobby. It will produce vegetables for you at all stages of complexity. You can begin with simple systems and develop more complex ones to suit your needs and interest (Photos 9 & 10).




All will give you a sense of accomplishment as you produce some of your own vegetables such as lettuce, herbs, tomatoes, cucumbers, peppers and ornamentals. As you gain experience you can learn more about hydroponic culture from hydroponic forums on the Internet as well as attending conferences held annually by hydroponic societies, universities, and private suppliers of hydroponic components. Many books are available also, including mine shown here on the website, that will teach you both the basics and more, should you wish to develop your own nutrients and systems. You may start with simple systems and work your way up to more sophisticated systems, developing them yourself or purchasing them from hydroponic outlets.


Conditions Suitable to Hobby Hydroponics:

Two limiting environmental factors on yields are light and temperature assuming that nutrition is provided at relatively optimum levels. Hobby hydroponic systems are generally operated in the environment of your home. The choice of light quality and intensity is important since natural sunlight will not be available. You want at least 5500 lux (510 foot candles) of light for a period of 14 to 16 hours per day. High-intensity discharge (HID) lighting is preferred over fluorescent as its quality and intensity is better. Within this category of lights, the metal halide (MH) light with a wider spectrum is better for indoor growing than the high-pressure sodium (HPS) ones. We want about 60 watts of light per square foot of growing area. Calculate the wattage of light required by multiplying 60 watts by the total growing area. Such lights, complete with reflectors and ballasts, may cost from $600 to $800 depending upon the wattage. Please refer to my book “Hobby Hydroponics” for more information on lighting.


Temperature in your home generally is favorable to most growing. However, if you have a larger hydroponic unit in a spare room or basement where you can control the temperature apart from the rest of the home, you can achieve more optimum ranges for your plants. Night temperatures should be about 5 to 10 F. less than day temperatures. For tomatoes, peppers and cucumbers a good temperature range is 65 F at night and 75 F during the day. For cool-season crops like lettuce the night temperature should be about 55 F and the day 60 to 65 F. Herbs will tolerate a wider range of temperatures than the above crops. During the summer with hot outside daytime temperatures your crops will benefit from air conditioning to keep temperatures within these ranges. However, during the summer you could also move your hydroponic system onto the patio or balcony or even in the back yard and take advantage of the natural sunlight and temperatures.


Plants growing outside receive ambient carbon dioxide levels of about 300 ppm (part per million). Levels in your house may be lower than that, especially in the winter months when outside ventilation is at a minimum. In such cases it would be beneficial to enrich the atmosphere with carbon dioxide from a small generator that operates on natural gas. These small units cost from $350 to over $500 depending upon their capacity which is a function of the volume of air in your growing room. Some modern homes may exchange the air in the house efficiently through the central heating-cooling system. In that case carbon dioxide levels may be adequate without enrichment. However, to achieve higher crop yields, carbon dioxide enrichment up to 1200 ppm will be beneficial.

3 thoughts on “Introduction to Hydroponics

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