Hydroponics, (from the Greek hydro, “water,” and ponos, “labor”), which is also called aquaculture, nutriculture, soilless culture, or tank farming, is the cultivation of plants in nutrient-enriched water, with or without the mechanical support of an inert medium such as sand or gravel.
Plants have long been grown with their roots immersed in solutions of water and fertilizer for scientific studies of their nutrition. Early commercial hydroponics adopted this method of culture. Because of the difficulties in supporting the plants in a normal upright growing position and aerating the solution, however, this method was supplanted by gravel culture, in which gravel supports the plants in a watertight bed or bench. Various kinds of gravel and other materials have been used successfully, including fused shale and clay and granite chips.
One of the earliest successes of hydroponics occurred on Wake Island, a rocky atoll in the Pacific Ocean used as a refueling stop for Pan American Airlines. Hydroponics was used there in the 1930s to grow vegetables for the passengers. Hydroponics was a necessity on Wake Island because there was no soil, and it was prohibitively expensive to airlift in fresh vegetables.
A wide variety of vegetables and florist crops can be grown satisfactorily in hydroponics. The principal advantage is the saving of labor by automatic watering and fertilizing. The disadvantages are high installation costs and the need to test the nutrient solution frequently.
The earliest published work on growing terrestrial plants without soil was the 1627 book Sylva Sylvarum or ‘A Natural History’ by Francis Bacon, printed a year after his death. Water culture became a popular research technique after that. In 1699, John Woodward published his water culture experiments with spearmint. He found that plants in less-pure water sources grew better than plants in distilled water. By 1842, a list of nine elements believed to be essential for plant growth had been compiled, and the discoveries of German botanists Julius von Sachs and Wilhelm Knop, in the years 1859–1875, resulted in a development of the technique of soil-less cultivation. Growth of terrestrial plants without soil in mineral nutrient solutions was called solution culture. It quickly became a standard research and teaching technique and is still widely used.
This is important as one of the most common errors when growing plants is over- and under- watering; and hydroponics prevents this from occurring as large amounts of water can be made available to the plant and any water not used, is drained away, recirculated, or actively aerated, eliminating anoxic conditions, which drown root systems growing in soil. In soil, a grower needs to be very experienced to know exactly how much water to feed the plant. Too much and the plant will be unable to access oxygen; too little and the plant will lose the ability to transport nutrients, which are typically moved into the roots while in solution. Two researchers developed several formulas for mineral nutrient solutions, known as Hoagland solution. Modified Hoagland solutions are still in use.
Important differences include:
Unlike soil, hydroponic nutrient solutions do not have cation-exchange capacity (CEC) from clay particles or organic matter. The absence of CEC means the pH and nutrient concentrations can change much more rapidly in hydroponic setups than is possible in soil.
Selective absorption of nutrients by plants often imbalances the amount of counterions in solution. This imbalance can rapidly affect solution pH and the ability of plants to absorb nutrients of similar ionic charge. For instance, nitrate anions are often consumed rapidly by plants to form proteins, leaving an excess of cations in solution. This cation imbalance can lead to deficiency symptoms in other cation based nutrients (e.g. Mg2+) even when an ideal quantity of those nutrients are dissolved in the solution.
Depending on the pH and/or on the presence of water contaminants, nutrients such as iron can precipitate from the solution and become unavailable to plants. Routine adjustments to pH, buffering the solution, and/or the use of chelating agents is often necessary.
As in conventional agriculture, nutrients should be adjusted to satisfy Liebig’s law of the minimum for each specific plant variety. Nevertheless, generally acceptable concentrations for nutrient solutions exist, with minimum and maximum concentration ranges for most plants being somewhat similar. Most nutrient solutions are mixed to have concentrations between 1,000 and 2,500 ppm. Acceptable concentrations for the individual nutrient ions, which comprise the total ppm figure, for plant varieties are found empirically by experience and/or by plant tissue tests in a laboratory.
Tools Common equipment:
Managing nutrient concentrations and pH values within acceptable ranges is essential for successful hydroponic horticulture. Common tools used to manage hydroponic solutions include:
Electrical conductivity meters, a tool which estimates nutrient ppm by measuring how well a solution transmits an electric current.
pH meter, a tool that uses an electric current to determine the concentration of hydrogen ions in solution.
Litmus paper, disposable pH indicator strips that determine hydrogen ion concentrations by color changing chemical reaction.
Graduated cylinders or measuring spoons to measure out premixed, commercial hydroponic solutions.
Chemical equipment can also be used to perform accurate chemical analyses of nutrient solutions. Examples include:
Balances for accurately measuring materials.
Laboratory glassware, such as burettes and pipettes, for performing titrations.
Colorimeters for solution tests which apply the Beer–Lambert law.
Using chemical equipment for hydroponic solutions can be beneficial to growers of any background because nutrient solutions are often reusable. Because nutrient solutions are virtually never completely depleted, and should never be due to the unacceptably low osmotic pressure that would result, re-fortification of old solutions with new nutrients can save growers money and can control point source pollution, a common source of nearby lakes and streams.
Often mixing hydroponic solutions using individual salts is impractical for hobbyists and/or small-scale commercial growers because commercial products are available at reasonable prices. However, even when buying commercial products, multi-component fertilizers are popular. Often these products are bought as three part formulas which emphasize certain nutritional roles. For example, solutions for vegetative growth (i.e. high in nitrogen), flowering (i.e. high in potassium and phosphorus), and micronutrient solutions (i.e. with trace minerals) are popular. The timing and application of these multi-part fertilizers should coincide with a plant’s growth stage. For example, at the end of an annual plant’s life cycle, a plant should be restricted from high nitrogen fertilizers. In most plants, nitrogen restriction inhibits vegetative growth and helps induce flowering.
The medium in which the plant’s roots grow is called the growing medium. It may include a wide range of substances like Rockwool, coconut fiber, perlite, vermiculite, sand, gravel, etc. This growing medium is a motionless substance which is not responsible for supplying nourishment to the plant. For the purpose of providing nutrients, a nutrient solution is used, which is a mixture of fertilizer and water. Thus, you have total control over the supplies of plants. You can easily adjust the pH and strength of the nutrient solution in order to ensure the right amount of nourishment for the plants. You can even use a timer, which is not very expensive to be sure that the plants get water and feeds on the right time.
Difference between “regular”, hydroponic, and organic fertilizers:
The fertilizers intended for use in soil or hydroponic fertilizers consist of three main nutrients: potassium, phosphorus and nitrogen. However, the major difference comes in the quantity of these nutrients in hydroponic fertilizers. They consist of adequate amount of these nutrients while the fertilizers meant for soil may contain these nutrients in improper amounts. The plants have to search for them in the soil for the amount they require, assuming that the soil contains them. The problem arises when one of these nutrients or all of them are not there in the soil. Sometimes, they also get depleted due to successive plantings.
The hydroponic fertilizers are more refined in form and have lesser impurities, which makes them more stable and also more soluble so that they have better absorption capacity.
On the other hand, organic fertilizers are different from soil and hydroponic fertilizers. They are different in composition and their process of delivering nutrients to the plants is also distinguished. They depend on synergistic activity of the microbes and bacteria to split the nutritional substances so that they can be easily taken up by the plants. Soil and hydroponic fertilizers give the nutrients to the plants in an easy to use form. Earlier, they used to be
mutually exclusive. But, in the last few years, various organic fertilizers have come to the market, whose formulations are refined for their application in hydroponics.
Micro nutrients-what are they?
They are also known by the name of trace elements, which are required for the healthy growth of a plant. Some of the micro nutrients include sulfur, calcium, magnesium, boron, copper, cobalt, iron, molybdenum, manganese, and zinc. If any of these nutrients are required by the plants but they do not get it, they undergo diseases, stress and become more prone to fungus, pest and bacteria. The plants may also have uptake problems with N-P-K fertilizer, which is being fed to them.
In such conditions, the plants will never be able to live the maximum potential of their genes in yield and growth. And, at extreme stages, they may even die. In the production of food crops, if the plants are deficit in nutrients, the animals or humans who consume them will also be deficient of the same nutrients.
Due to successive years of farming on the same lands, most of the commercially produced foods today have lesser nutrients. That is why; the number of such families is increasing which like to grow their own crops, or at least fruits. If you are growing plants in soil, you must remember to renew the soil between plants. If you are growing plants hydroponically, you must avail yourself of hydroponic fertilizer for the plants, which is capable of providing the trace elements.
Fertilizer solution is pumped through periodically, the frequency and concentration depending on the plant and on ambient conditions such as light and temperature. The solution drains into a tank, and pumping is usually automatic. The solution is composed of different fertilizer-grade chemical compounds containing varying amounts of nitrogen, phosphorus, and potassium—the major elements necessary for plant growth—and various trace, or minor, elements such as sulfur, magnesium, and calcium.
Since you have decided to build a hydroponics system, you will definitely want to grow your favorite plants in it. Although it is easy to start these systems, you need to take care of a few things so that the end results are positive. Obviously, you would not want to waste all your efforts just because you “forgot” to be cautious. You can keep these tips in mind to maintain your hydroponics system to the best.
Maintain cleanliness of the system:
You must clean your grow room prior to installing the hydroponics system. Before you set up the system and keep it in the grow room, you must clean your plant box using a 10% bleach solution. Cut off the dead leaves of the plants and eliminate them from the room. Dead organic matter decays and attracts fungus. You must also take out diseased plants so that there is no chance of spreading of infection. Whenever you change water in the reservoir, you must wash the tank properly with a 10% bleach solution. In case, you are using large trays for your slabs and blocks, you must wash them too, particularly if you doubt that the roots are susceptible to rotting.
Ebb and flow system:
For this system, you need a timer that can be set at an interval of 5 minutes, so that a complete cycle will soak your stone wool for a time period of 10 minutes. In order to prevent building up of salt, it is recommended that you must top water the plants weekly. Use the same solution in the reservoir. But, do not use plain water to top water the plants. The plants may get shocked! In addition, keep a tray handy, which has deep grooves so that the water should drain away from the slabs.
The pH should not ever go below 5 which is very acidic! Also, make sure that the stone wool is not damaged.
If the pH is below 5 and above 7, the plants are not able to absorb the nutrients. A couple of hours before you place the plants, do not forget to soak the stone wool using water with pH level 5.5. You can also flush the stone wool with the nutrient solution with pH 5.5, drain to waste, then you can place the stone wool in the system.
The pH level in the reservoir will go up in the course of vegetative growth, which is completely natural. It implies that your plant is happily growing. But, pH levels also rise due to algae growth and high temperature. Thus, you must keep an eye on pH. Most plants show good growth at pH level 6.0.
Here is the big death trap in every hydroponics system. Because all of the plants are fed from a common nutrient reservoir, any contamination, virus, fungus or chemical deficiency is fed to ALL of the plants and this may kill them – wiping out your entire crop and months of hard work in a just a few hours. A power failure, pump malfunction, or pipe breakage will also prove fatal. It is highly recommended that you completely inspect your system daily and you must clean and change the complete reservoir nutrient solution every week. Even after taking every precaution, the solution may fall short of some important micro nutrients or get infected due to rotting plant roots. If the reservoir consists of nutrient solution that is diluted or is the ready to use kind, you can use lemon juice or phosphoric acid to lower the pH levels.
Learn from your own notes:
Make a journal which keeps a track of EC, light level pH, temperature, and CO2 for each day. This will enable you to learn from your own successes and mistakes. This habit will also help you to ask for solutions from the supplier when you give them a list of your questions.
Check your basics:
There is a deficiency of calcium in leaves sometimes. Before you accuse the plant food for unhealthy plants, you must check the journal. Every element should be in balance. Change any one parameter and watch for effects. Sometimes, the water of the reservoir becomes very cold. You can put in a heating element in it to reach a temperature of 70 degrees Fahrenheit. You can also put a heating mat under the reservoir.
If you are facing problems in getting the plants to place fruits and flowers, you can try to make a bigger difference between the temperatures of day and night. If nothing works, you can try to increase the injection of CO2 during daytime.
Deficiency of calcium:
If you find that the youngest leaves are curled downward, it means that there is a deficiency of calcium in the plant. And, in case, the older leaves are seen curled, then there is something not right in the root zone. This reduces the uptake of calcium. Deficiency of calcium is a result of inadequate movement of water through different parts of the plant. You must remember that calcium gets transported only through the stream of water, not through the stream of nutrients. Thus, it is usually related to change in climate. Higher humidity prevents uptake of calcium even if is present in sufficient amount in the nutrient solution.
Deficiency of calcium in fruits:
Large fluctuations in the humidity levels during day and night disrupt the flow of calcium within different parts of the plants. This results in BER or blossom-end rot. Poor development of roots is also a major cause of calcium deficiency in fruit bearing plants. When the roots do not grow actively, new tips of roots do not form properly and the uptake of calcium gets reduced.
Since there is no soil involved in hydroponic crops, there is no fuss with weak soils, soil temperature or soil improvement. The system itself is capable of providing perfect conditions to the plants for their growth. However, there is one disadvantage of this system. Hydroponic plants have weaker system of roots. But, if you do not have perfect soil in your garden, hydroponics is best for you.
Climate and speed:
Plants grow faster in hydroponics system than in soil, which means more vegetation per year along with more profit. Moreover, with the former system, you can grow crops round the year indoors without worrying about climatic conditions outside.
Time, equipment and labor costs:
Though the initial set up costs of hydroponics are higher than traditional farming, the expenses are spread over time and stabilize later. Since the rate of production is high, money is saved when you do not have to spend much on labor and time.
Reaction time of diseases:
Hydroponic systems can fail and die in just a few hours. This is one area where conventional farming has an upper hand. Plants in the ground take a longer amount of time to react to soil borne diseases. Thus, the conventional farmers get more time, even several days, to fight the problems of plants. Farmers may lose one section, or several rows of plants, but the rest will survive.