Hydroponics
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Introduction
Hydroponics is a type of horticulture which involves growing plants (usually crops) without soil, by using mineral nutrient solutions in an aqueous solvent. Terrestrial plants may grow with their roots exposed to the nutritious liquid, or, in addition, the roots may be physically supported by an inert medium such as perlite, gravel, or other substrates. Despite inert media, roots can cause changes of the rhizosphere pH and root exudates can affect rhizosphere biology. Plants commonly grown hydroponically, on inert media, include tomatoes, peppers, cucumbers, strawberries, lettuces, cannabis, and model plants like Arabidopsis thaliana.
Advantages of Hydroponics
The most obvious benefit of hydroponic gardening is increased growth rate of most plants. Plant grown via hydroponics at least 20% faster than soil gardening. Hydroponics will also typically yield at least 25% more than their soil counterparts.​
Another advantage of hydroponics, is a notably decrease in water usage. To grow 1 kilogram (2.2 lb) of tomatoes using intensive farming methods requires 400 liters (88 imp gal; 110 U.S. gal) of water; using hydroponics, 70 liters (15 imp gal; 18 U.S. gal); and only 20 liters (4.4 imp gal; 5.3 U.S. gal) using aeroponics. Since hydroponics takes much less water to grow produce, it could be possible in the future for people in harsh environments with little accessible water to grow their own food.
Disadvantages of Hydroponics
The biggest downside of hydroponics is the cost of infrastructure for large commercial operations. Some hydroponics may be prohibitively expensive for hobbyists as well. However, you can build many of these systems yourself, which can significant reduce the cost.
Another negative is the learning curve getting the hang of running a system successfully. You don't have to be a botanist to do hydroponics, but it is definitely more difficult than soil based methods. This is difficulty is due to having to create an artificial environment where you provide the water, nutrients, light, and everything else the plant needs. This requires careful monitoring of those inputs in order for your plants to survive. If one of those elements is out of balance, or you have an equipment failure like a pump dying, then your entire garden can be put at risk.​[3]
Irrigation Methods
There are two main variations for each medium: sub-irrigation and top irrigation. For all irrigation methods, most hydroponic reservoirs are now built of plastic, but other materials have been used including concrete, glass, metal, vegetable solids, and wood. The containers must light to prevent algae and fungal growth in the nutrient solution.
Static solution culture
In static solution culture, plants are grown in containers of nutrient solution, such as glass Mason jars (typically, in-home applications), pots, buckets, tubs, or tanks. The solution is usually gently aerated but may be un-aerated. If un-aerated, the solution level is kept low enough that enough roots are above the solution so they get adequate oxygen. A hole is cut (or drilled) in the top of the reservoir for each plant; if it a jar or tub, it may be its lid, but otherwise, cardboard, foil, paper, wood or metal may be put on top. A single reservoir can be dedicated to a single plant, or to various plants. Reservoir size can be increased as plant size increases. A home-made system can be constructed from food containers or glass canning jars with aeration provided by an aquarium pump, aquarium airline tubing and aquarium valves. Clear containers are covered with aluminum foil, butcher paper, black plastic, or other material to exclude light, thus helping to eliminate the formation of algae.
The nutrient solution is changed either on a schedule, such as once per week, or when the concentration drops below a certain level as determined with an electrical conductivity meter. Whenever the solution is depleted below a certain level, either water or fresh nutrient solution is added.
A Mariotte's bottle or a float valve, can be used to automatically maintain the solution level. In raft solution culture, plants are placed in a sheet of buoyant plastic that is floated on the surface of the nutrient solution. That way, the solution level never drops below the roots.
Plants are grown in containers of nutrient solution, such as plastic bottles, tubs or any other in-home applications
There are can be one to many plants per reservoir and reservoir can be increased as plant size increases
Solutions is usually gently aerated; however, if un-aerated, solution level is kept low so roots are high enough to get adequate oxygen
Clear containers are covered with aluminum foil or other material to exclude light so that formation of algae is eliminated
Nutrient solutions is changed either on a schedule or when concentrations drops below a certain level as determined by a device, such as a moisture sensor
Passive Hydroponics
Passive hydroponics systems are the some of the simplest growing methods. An inert porous growing medium is used to transport water and fertilizer to the roots by capillary action. Water and fertilizer are held in a reservoir and conducted to the roots as necessary, reducing labor and providing a constant supply of water to the roots. In the simplest method, the pot sits in a shallow solution of fertilizer and water or on a capillary mat saturated with nutrient solution. Since routine maintenance is much simplified, passive hydroponics can reduce the labor required to maintain a large collection of plants.
Kratky Method
The Kratky method is a passive hydroponic technique for growing plants suspended above a reservoir of nutrient-rich water. Because it is a non-circulating technique, no additional inputs of water or nutrients are needed after the original application, and no electricity, pumps, or water and oxygen circulation systems are required. The Kratky method has applications both for commercial food production and as a small-scale and low-maintenance technique for home growers.It has been described as "the simplest hydroponic system."
Continuous-flow solution culture
In continuous-flow solution culture, the nutrient solution constantly flows past the roots. It is much easier to automate than the static solution culture because sampling and adjustments to the temperature, pH, and nutrient concentrations can be made in a large storage tank that has potential to serve thousands of plants.
Nutrient Film Technique
A popular variation is the nutrient film technique or NFT, whereby a very shallow stream of water containing all the dissolved nutrients required for plant growth is recirculated in a thin layer past a bare root mat of plants in a watertight channel, with an upper surface exposed to air. As a consequence, an abundant supply of oxygen is provided to the roots of the plants. A properly designed NFT system is based on using the right channel slope, the right flow rate, and the right channel length. The main advantage of the NFT system over other forms of hydroponics is that the plant roots are exposed to adequate supplies of water, oxygen, and nutrients. In all other forms of production, there is a conflict between the supply of these requirements, since excessive or deficient amounts of one results in an imbalance of one or both of the others. NFT, because of its design, provides a system where all three requirements for healthy plant growth can be met at the same time, provided that the simple concept of NFT is always remembered and practiced. The result of these advantages is that higher yields of high-quality produce are obtained over an extended period of cropping. A downside of NFT is that it has very little buffering against interruptions in the flow (e.g., power outages). But, overall, it is probably one of the more productive techniques.
The same design characteristics apply to all conventional NFT systems. While slopes along channels of 1:100 have been recommended, in practice it is difficult to build a base for channels that is sufficiently true to enable nutrient films to flow without ponding in locally depressed areas. As a consequence, it is recommended that slopes of 1:30 to 1:40 are used. This allows for minor irregularities in the surface, but, even with these slopes, ponding and water logging may occur. The slope may be provided by the floor, benches or racks may hold the channels and provide the required slope. Both methods are used and depend on local requirements, often determined by the site and crop requirements.
As a general guide, flow rates for each gully should be one liter per minute. At planting, rates may be half this and the upper limit of 2 L/min appears about the maximum. Flow rates beyond these extremes are often associated with nutritional problems. Depressed growth rates of many crops have been observed when channels exceed 12 meters in length. On rapidly growing crops, tests have indicated that, while oxygen levels remain adequate, nitrogen may be depleted over the length of the gully. As a consequence, channel length should not exceed 10–15 meters. In situations where this is not possible, the reductions in growth can be eliminated by placing another nutrient feed halfway along the gully and halving the flow rates through each outlet.
References
Wikipedia, Hydroponics (2021)
Wikipedia, Kratky Method
Kevin Espiritu, How to Set Up The Kratky Hydroponics Method (Tutorial), Epic Gardening (2021)
Kevin Espiritu, Hydroponic Systems, Epic Gardening (2021)
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