, Research Paper
Hydroponics: Growing Without Soil
The science of growing plants without soil has been known and used for more than one-hundred years. The word hydroponics , however, is comparatively new. Dr. W.E. Gericke is usually given credit for coining the word, which translated from Greek, means working water . The famous hanging gardens of Babylon were probably on of the first attempts to grow plants hydroponically. The work of Dr. Greicke in the 1920 s and 1930 s in California, however, is generally considered the basis for nearly all forms of hydroponics. During the 1940 s at Purdue University, Robert B. and Alice P. Withrow developed another hydroponic method. Their process was called Nutriculture. Nutriculture varied from Dr. Gericke s method in that gravel was used as a rooting medium.
After World War II a number of commercial installations were built in the United States. The majority of these were located in Florida. Most were out of doors and subject to the rigors of the weather. Poor construction techniques and operating practices caused many of them to be unsuccessful and production inconsistent.
How is the quality of the food today affected by the methods of Hydroponics of today?
The growing media that is used for gardening greatly effects the production of the plants. If sand is used as a medium it should be tested thoroughly for any residue that might cause infected growing medium. The sand should be cleaned at least every three of four weeks. Leaching is also a major step, it is to be done at the end of each crop cycle ( Jones 69-70). Sand that is used for the medium should have sawdust mixed with it to allow for better drainage. The sawdust also makes the sand lighter and not pact together as easy ( Bridwell 86).
Gravel is another medium, it is used more often because it is easier to clean. If gravel is used round, smooth, river-type is preferred. Granitic types are the best because of its hardness. Whatever type of gravel that is purchased must be thoroughly washed and cleaned to get rid of any calcareous on the gravel. The size is also a factor when selecting gravel. The pieces of gravel should be no smaller than a quarter inch in diameter and larger than a half inch. Crushed stone is not preferred because the sharp edges can injure the root system.
The sterilizing process is an easy, but a long and tedious job. Flood the beds with fresh water, which has enough sulphuric acid to lower the pH level to the three or four range. The solution should be left on the gravel for at least 12 hours. Flush the gravel thoroughly with fresh water. Add a fresh solution containing one quart Clorox for every one-hundred gallons of water. Leave the solution for at least six hours. After that is done completely drain and flush thoroughly with clear water at least twice. Do this again at the end of each crop cycle ( Jones 67-9).
The most common diseases for plants are the various types of fungi. A greenhouse with a controlled environment is pretty easy to prevent fungus-type diseases. The environment has to have a warm temperature, low humidity, and proper air circulation. If a long period of cold, cloudy, and humid weather occur, the temperatures can not remain at minimum levels or the plants will suffer from some type of fungus ( Jones 112).
Leaf molds are just one of many types of funguses common in tomato plants. The fungi can be identified by small patches of spores on the leaves. These grayish spots appear on the older leaves first. On the top of the leaves will appear velvety green or brownish spots. Once these begin to form, the plant should not be moved or the spores will spread through the air to the other plants in the greenhouse. Some fungicides that can be used to control leaf molds are Maneb, Bravo, and Dithane 22 ( Zim 110).
Botrytis is the worst fungus found in tomato plants. Botrytis is a gray mold that not only forms around the base of the stem and destroys it, but also attacks the fruit around the calyx, causing it to rot in a few hours. A cold and wet environment provides the perfect place for Botrytis to grow. Botrytis spores will not live in a hot, dry environment. This fungus can also be killed with a fungicide. A few of these are; Botran, Bravo, and Exotherm-Termil ( Bridwell 49-51).
The potato virus, also known as double-streak virus, is another disease that can literally wipe-out an entire crop. This virus is caused by using soil that was previously used to grow potatoes in. The first symptoms noted are elongated brown streaks on the stem of the plant. The fruit will be pitted and splotched and will look as if the plants have smallpox or measles. Under no circumstances should potatoes and tomatoes be grown in the same system or the same greenhouse. There are several sterilizers that will kill the potato virus, such as Methyl Bromide, but are strongly used as a last resort ( Jones 114).
Tobacco mosaics is another common disease that affects tomato plants. If a grower smokes or carries tobacco in a greenhouse it could cause serious crop damage. It is recommended that if a grower uses tobacco that he wash his hands in a good disinfectant before handling the plants. Mosaic symptoms seem to occur in a greenhouse where light conditions are not good and where the temperatures are too cool, especially in shaded areas. Tobacco is not the only thing that causes mosaics. A hydroponics unit in California was experiencing a problem with its plants not growing right. After lots of study and research of the area they found that cropdusting planes were refilling at an airport over a mile away ( Jones 114-15).
Insects are another major concern when growing plants normally or hydroponically. Pepper plants and Tomato plants are greatly affected There are a number of different insects that will attack and destroy a crop. To see these small insects a magnifying glass is needed. It is easy to tell if the plants are being affected. The back of the leaves will have small black dots on them ( Resh 140). The spider mite feeds by sucking the juices from the leaves. The mites will spread very quickly through a crop once they get a foothold (Coene 11). Looking at the fruit and foliage is also a way to tell if the plant is being affected. The fruit and foliage will begin turning pale and yellow. The underneath of the leaves will begin to have very fine webs ( Coene 12).
There is a wide variety of pesticides for spider mites. Some, of course, work longer and better than others. Thiodan, Dibrom, and Sevin are just a few. These pesticides will kill the adults and at the same time break the hatching cycle. If not stopped, spider mites will very rapidly defoliate a tomato or cucumber crop ( Bridwell 136-37).
White flies are another unwanted pest. Tomato and cucumber plants are highly apt to attracting these pests. The white fly builds up a resistance to any pesticide very rapidly ( Zim 112). White flies are usually located on the undersides of the leaves and has a triangular white body. The white fly secretes a honeydew sticky substance on the leaves; later a black fungus often develops as a secondary infection. If not take care of immediately with pesticides or other means the plants may, in great numbers, die
( Bridwell 113).
The white fly will build up a resistance to any pesticide very quickly. Only by extreme care can they be controlled. The pesticides that are used should vary each time they are used. The best hope for controlling these insects will eventually be through biological means. A new control for the flies, Prescription Treatment # 1200 containing Resmethrin, is being reported as very effective by growers who have used it ( Bridwell 137-38).
Tomato and pepper plants are just a few of the numerous plants that pinworms munch on. This pest is the hardest to eliminate. The pinworm like other members of the worm family, comes from a moth egg. The moths lay eggs in the tops of the plants and when the eggs hatch, the worm develops between the leaf tissues. A pinworm may also be found under the calyx on tomatoes, in the stems of the plant, and where two tomatoes make contact in a cluster ( Jones 117-18). It is very easy to tell if pinworms are on the fruit and foliage. The fruit will have holes and deadspots on them and the calyxes will be eaten off. The leaves will have holes in them, that look like they have been tore off ( Zim 120).
There are not many pesticides that will kill pinworms. The best ways to kill them are to pull them off and squash or cut them into. They can be killed by a pesticide but they have to be doused in it ( Coene 14).
There are many types of cultures to grow plants hydroponically. The peat, perlite, and vermiculite culture is used primarily for small plants and herbs. Some materials that go along with this culture are: an air pump, solution reservoir, and perforated tubing. The air pump can be simply an aquarium pump. The pump is used to disperse air into a tube submerged in the nutrient solution. This causes the nutrient to flow up the tube to the top of the growing medium. The tube is perforated along the top to allow the solution to bleed from the tube along its length to the surface of the medium. After flowing through the medium and roots it goes back into the solution reservoir ( Resh 51).
The solution reservoir can be many different sizes depending on the growing tray size. A typical size is two foot by six foot for a slightly smaller growing tray. It should be about three to four inches deep, and can be constructed of wood, lined with vinyl or polyethylene. Wood or aluminum cross bars at eighteen inch centers not only to prevent the tank from bowing outward but also support the upper growing tray ( Resh 56). The perforated tube is very essential for the garden to work. The tube brings the nutrient solution to the roots of the plants. The tube should have small holes on each side cut out for the solution to be distributed all over the bed ( Resh 51).
This type of culture is ideal for growing plants like herbs, bedding plants for later transplanting, and leaf lettuce. First fill the compartment with coarse vermiculite. Sow the seeds directly into the media and cover with a finer layer crushed by hand. Moisten the seeds and media and then cover he tray with raw water, then cover the tray with black polyethylene sheeting for several days until germination occurs (Resh 56). Lettuce is another ideal plant for this type of culture. There are many different varieties of lettuce that can be grown hydroponically. Buttercrunch, Domineer, and Satonia are just a few of the varieties. It is necessary to allow a space six inches by six inches for each plant. Lettuce can thrive under the same environment conditions as tomatoes, but it can be grown at far lower temperatures. The most optimum production is at lower temperatures. Fifty degrees is the best temperature, but it is possible to grow a good lettuce crop at forty degrees ( Jones 104-05).
The vertical sack culture, also known as column culture, is used mainly for flowering plants, house plants, and strawberries. The pump can be a simple aquarium pump if a better pump can not be found. The pump is used to circulate the nutrient solution through the supply lines to all of the columns and down through the feed lines( Resh 59). The columns are made out of two and half inch PVC pipe with drainage holes in the bottom of the pipes to return the nutrient solution back to the nutrient reservoir. There is no advantage in growing vine crops in a vertical position. They are normally trained up string supports, creating their own vertical canopy ( Resh 60).
House plants are just one of the many plants that can be grown in vertical culture. Tulips, amaryllis, and gladiolus grow very good if not better, through hydroponics. When growing these flowers the corms can be planted side by side with one inch or less sperarating them. They should be placed in the growing medium so that the bottom of the corm just reaches the solution level when the beds are irrigated. Almost any other type of flower can and has been grown hydroponically with excellent results ( Jones 108).
Strawberries grown very good in this type of culture. The only problem in growing strawberries is that they need far less water than most plants. Overwatering wil result in little or no production. For this reason it is recommedded that they be grown in a seperate bed. When growing strawberries always allow each plant an area of six inches square ( Jones 94).
Flowering plants can be grown from cuttings. Cuttings will root very quickly in blocks, but there are also rooting stimulators available that accelerate root growth. These are especially good for hard-to-propagate species. Most people will want to grow a number of varieties, both vegetable and flower, in the same unit. This can certainly be done. Results will be satisfactory for most growers if a median is established for all of the factors ( Jones 108).
The growing of food over the years has been greatly improved. Hydroponics is an easy way to grow food with minimum work and less prone to diseases. Hydroponics has greatly increased in the way foods are grown today. This process is used to grow almost all of the foods we eat today. There are very few steps to be taken when starting a hydroponical garden. Some of the supplies that are needed are: a submersible pump, PVC pipe, plastic tubing, metal or wood to build the trays with, and a good culture to grow the plants in. These are some of the major things tht it takes to grow plants hydroponically.
The food that is grown today is less prone to viruses, insects, and temperatures that affect most of the plants that are grown normally in gardens in the backyard.
Bridwell, Raymond. Hydroponic Gardening California: Woodbridge, 1982.
Coene, Trisha. The Ins and Outs of Soilless Gardening : The Growing Edge. Vol. 8, no. 4, summer
Jones, Lem. Home Hydroponics: … and how to do it! New York: Crown, 1977.
Resh, Howard M. Hydroponics: Home Food Gardens. California: Woodbridge, 1990.
Zim, Herbert S. Plants New York: Harcourt, 1947.