Hydroponics comes from the Greek word “hydro” meaning water, and “ponos” meaning labor. Hydroponics is often defined as “the cultivation of plants in water with nutrient solution.” It has since determined that many different aggregates or media will support plant growth; In other words, hydroponics is gardening without soil.
hydroponics – “A technology for growing plants in nutrient solutions (water containing fertilizers) with or without the use of an artificial medium (sand, gravel, vermiculite, rockwool, perlite, peat moss, coir, or sawdust) to provide mechanical support.” In addition, some scientists defined the growing of plants without media as “liquid hydroponics” and with media as “aggregate hydroponics.”
A hydroponicist is defined as one who practices hydroponics, and hydroponicum defined as a building or garden in which hydroponics is practiced. Hydroponics can also be referred to as a technique in which plant roots are suspended in either a static, continuously aerated nutrient solution or in a continuous flow or mist of nutrient solution. The growing of plants in an inorganic substance (such as sand, gravel, perlite, or rockwool) or in an organic material (such as sphagnum peat moss, pine bark, or coconut fiber) that are periodically watered with a nutrient solution should be referred to as soilless culture farming.
Advantages of hydroponics
- Plants can be grown anywhere year – round,
- Greater control over growing conditions for increased crop yields and faster growing time,
- No weeding required,
- Saves water, up to 90 percent,
- No need for crop rotation,
- Plants can be spaced close together and stacked vertically,
- Materials can be reused.
Limitations of Hydroponics
- High initial costs,
- High technical and plant physiology knowledge,
- Periodic work routines,
- Efficient electrical systems,
- Control of nutritional solutions and daily measurements of liquid nutrients to avoid excess salinization,
- Microbial diseases can spread quickly and pests needs to be controlled.
Some Hydroponic terms includes: Aqua (water) culture, Hydroculture, Hutriculture, Soilless culture, Soilless agriculture, Tank farming, and Chemical culture. A hydroponicist is defined as one who practices hydroponics, and hydroponicum defined as a building or garden in which hydroponics is practiced.
Nutritional quality of hydroponically grown produce
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.
Hydroponics versus Soil system
There is no real difference as far as a plant is concerned in the nutrients it receives from hydroponics compared with normal soil gardening or organic gardening. For all three growing methods:
- the plant takes in and uses exactly the same molecules from the air
- the plant needs exactly the same temperature, light and moisture conditions
- the plant absorbs exactly the same plant nutrients into its roots.
The only real differences are in the way the nutrients are supplied to the plant:
- With organic gardening, nutrients are supplied as complex chemical molecules, which are from the tissues of decomposing animals or plants (or their by-products). These complex molecules are broken down in the root zone to form much simpler compounds which are then able to be taken in by the roots of the plant.
- With soil gardening, the soil contains both simple and complex compounds. Fertilizers applied are both simple and complex compounds. The simple compounds are absorbed directly. The complex compounds are broken down and then absorbed.
- With hydroponics, nutrients are applied as the same simple chemicals that occur in soil, or which organic compounds in soil break down to form. They are in a ready-to-use state as soon as applied.
Plant Growth Requirements:
All plants require nutrients, water, light, and air to grow. A plant grown in soil obtains nutrients and water from the soil. With hydroponics, water and nutrients are always available. Sunlight and air are readily available in an outdoor hydroponic system. For an indoor system, adequate light source and good air circulation must be provided. Metal halide lamps, sodium vapor lamps, fluorescent lights used in conjunction with incandescent light bulbs provide adequate light. Plant roots must have oxygen available to keep them alive. Healthy roots (which are white in color) are responsible for the uptake of all nutrients for the plant. Air circulation around leaves is important since it mixes the air and allows the plant to draw out the carbon dioxide necessary to carry on photosynthesis. Air circulation also helps prevent fungal diseases caused by moist, stagnant conditions. Indoor units often have a small fan to circulate the surrounding air.
Hydroponic growing systems
There are six basic types of hydroponic systems:
- Wick (Sub-Irrigation system)
- Raft/Floating system
- Ebb and Flow (or flood and drain system)
- Drip (with either a recovery or non-recovery process)
- N.F.T. (Nutrient Film Technique)
Hydroponic systems can also 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 (N.F.T, Raft/Floating and Aeroponics Systems).
- Medium culture systems use a solid substrate, such as sand, to support the plant root structure (Ebb and Flow, Drip and Wick/Sub-Irrigation Systems).
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:
- Nutrient film technique (NFT): In this method, Plant roots are placed in a small-diameter PVC tube or trough, and the nutrient solution flows across the roots forming a nutrient-dense film of water around them, the nutrient solution is pumped constantly. When the nutrient solutions reach the end of the channel, they are sent back to the beginning of the system. This makes it a recirculating system, here the plants roots are not completely submerged, which is the main reason for naming this method NFT. Roots dry out rapidly however during power outages or equipment failure when the supply nutrient solution is interrupted. NFT systems can be open or closed.
- Raft or floating system: Plants are supported by sheets of Styrofoam floated on aerated nutrient solution. A reservoir is used to hold the nutrient solution. The roots hang through small holes in the Styrofoam and are suspended in the solution. In this system, an air pump is used to oxygenate the water, preventing the roots from drowning. Raft systems are closed, and the nutrient solution must be frequently monitored and adjusted.
- Aeroponics: Plants are placed in a supporting container; the roots are suspended in air. The roots are misted with nutrient solution rather than being immersed in it i.e. Nutrients are sprayed, every few minutes, directly to the roots, which provide a light layer of nutrients. Aeroponic systems can be open or closed. This is the most sophisticated and high-tech method. This system requires a regular monitorization of pumps to avoid any failure.
Medium-culture systems use one of the following methods:
- Ebb-and-flow system (“flood and drain”): This system utilizes a grow tray and a reservoir that is filled with a nutrient solution. Nutrient solution is pumped from a reservoir into the grow bed, flooding the medium. Nutrient solution drains back to the reservoir by gravity. The pump periodically floods the grow tray with nutrient solution, which then slowly drains away. In this system, plants are normally grown in mediums like rockwool or gravel, but if they need a substantial amount of moisture, this is substituted with vermiculite or coconut fiber due to their high capacity of excess moisture retention. This is an example of a closed system, in which the nutrient solution is recycled.
- Drip system: Nutrient solution is provided to plants, supported in a solid medium, by drip irrigation. Modifications of this system have resulted in various commercial applications, such as the tower garden, in which plants are supported in a vertical PVC pipe by a porous medium. Nutrient solution is applied from the top of the pipe by a drip emitter. Nutrient solution can be either recycled (closed) or discarded(open).
- Sub-irrigation (or Wick) System: Plants are grown in a porous medium. Nutrient solution is transported to the roots by high capillary action. This system is passive, with no moving parts, which means that nutrients are stored in a reservoir and moved into the root system by capillary action. The grower using this system can use a variety of growing media such as perlite, vermiculite or coconut fibre. The wick system is easy and inexpensive to set-up and maintain. The drawback of this system is the poor oxygenation of plant roots and the large amount of nutrient solution that is required to reach efficiently to the plant root system, also large plants tend to draw and use the nutrient water at a faster rate than the wick can supply it.
Media selection for medium-culture systems
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, 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.
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).
Managing the hydroponic system
1. 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.
2. 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.
- Steam sterilization is effective at 180F for at least a half hour, and is effective at cleaning beds up to 8 inches in depth.
- Chemical sterilization is used when steam sterilization is not feasible. Bleach is commonly used and should be applied at a concentration of 10,000 parts per million. The solution should be allowed to sit on the medium for half an hour, and then the medium should be rinsed thoroughly. Other options are available.
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.
Equipment for Hydroponics
Submersible or ordinary water pumps, Ec meter, and pH meter are the essential equipment necessary to operate a circulating hydroponics. PVC pipes can be used as channels in these systems.
1. PVC Pipes: Type 400 or class 4 100 mm PVC pipes have to be used in circulating hydroponics as the channels. PVC pipes with thinner walls will sag and thereby reduce the flow rate of nutrient solution. The result will be lack of oxygen supply for the plant roots. UV resistant pipelines are preferable. Painting these pipes white will prevent the increase of nutrient solution temperature. The flow rate required in hydroponics is very small ranging from 1 – 3 litres per minute. Therefore, an over-flow pipe will have to be fitted to adjust the flow rate.
2. Water Pumps: The water pump must be made up of materials that are non-reactive with nutrient salt solution. Stainless steel shaft, polycarbonate or stainless-steel impeller, pump- house and water seal must be there in the pump to be used in hydroponics.
3. pH and Ec Meters: Simple and portable Ec (Electrical conductivity) meter and pH meter must be used to monitor and maintain the Electrical conductivity and pH at correct levels. [pH = degree of acidity].
4. Timer and Oxygen Detection Sensor: When the plants are small, their oxygen requirement is low. Therefore, the nutrient solution circulating time period can be limited. Limiting the circulating time periods can also reduce the electricity consumption. For this purpose, a timer may be used to set the circulating time manually or an oxygen concentration detection sensor may be included in the system, so the sensor can activate the pump whenever the oxygen concentration of the nutrient solution level goes down.
5. Nurtimeter: In addition to the Electrical conductivity, this meter helps measure the nutrient contents of the solution.
6. Pollinators: This simple electrical device vibrates the individual plants when touch them so that pollination is facilitated inside the protected structures.
7. Blowers: These devices help send airflow through the plants so that plants shake and pollens are distributed to facilitate pollination inside protected structures.
The goals of attaining food security and environmental protection can be achieved through hydroponic systems. Hydroponic farming enables agriculture even in those areas where there is no soil available such as deserts, polar regions, waste lands and constructed areas such as house, apartments etc.