What are hydroponic systems and how do they work?
Hydroponics is the art of gardening without soil. Hydroponics is a Latin word meaning "working water". In the absence of soil, water does the work by providing plants with nutrients, hydration, and oxygen.
Using minimal space, 90% less water than traditional agriculture, and ingenious design, hydroponic gardens grow beautiful fruits and flowers in half the time it takes in soil.
Although the technology sounds modern, the history of hydroponics dates back to the famous Hanging Gardens of Babylon, one of the Seven Wonders of the Ancient World. The Euphrates River was diverted into channels that cascaded down the walls of the lush gardens. In the XIII century, Marco Polo wrote that he had seen floating gardens in China. Hydroponics, however, is far from merely an ancient innovation. In the 90s of the last century, NASA grew aeroponic bean seedlings in zero gravity aboard a space station, opening up the possibility of sustainable agriculture in space. Hydroponics remains a timeless and dynamic method of conserving water and producing crops.
What is hydroponics?
Hydroponics is the cultivation of plants without soil. Hydroponic flowers, herbs, and vegetables are planted in an inert medium and supplied with nutrient-rich solutions, oxygen, and water. This system encourages rapid growth, more abundant yields, and higher quality. When a plant is grown in soil, its roots constantly search for the nourishment needed to sustain it. If a plant's root system is exposed directly to water and nutrients, the plant does not have to expend energy to sustain itself. The energy the roots would use to obtain food and water can be redirected towards the plant's maturation. As a result, leaf growth, fruiting, and flowering are more successful.
Plants sustain themselves through a process called photosynthesis. Plants capture sunlight using chlorophyll, the green pigment in their leaves. They use light energy to split the molecules of water absorbed through their root systems. Hydrogen molecules combine with carbon dioxide to produce carbohydrates, which plants use as food. Oxygen is then released into the atmosphere, a crucial factor in keeping our planet habitable. Plants do not need soil to photosynthesise. They need soil to supply them with water and nutrients. When nutrients are dissolved in water, they can be delivered directly to plant root systems through flooding, spraying, or immersion. Innovations in hydroponics have shown that direct exposure to nutrient-rich water can be a more efficient and versatile growing method than traditional irrigation.
How does hydroponics work?
Hydroponic systems work by allowing fine control over environmental conditions such as temperature and pH balance, while maximising exposure to nutrients and water. Hydroponics operates on a very simple principle: give plants exactly what they need, when they need it. Hydroponics applies nutrient solutions tailored to the needs of the particular plant being grown. These systems allow you to control exactly how much light plants receive and for how long. pH levels can be monitored and adjusted. In a highly customised and controlled environment, plant growth accelerates.
Controlling a plant's environment reduces many risk factors. Plants grown in gardens and fields are exposed to numerous variables that adversely affect their health and growth. Fungi in the soil can spread plant diseases. Wild animals such as rabbits can devour ripening vegetables in your garden. Pests such as locusts can descend on crops and destroy them in a single afternoon. Hydroponic systems eliminate the unpredictability of growing plants outdoors and in the ground. Without the mechanical resistance of soil, seedlings can mature much faster. By eliminating pesticides, hydroponics produces much healthier, higher-quality fruits and vegetables. Free from obstacles, plants can grow vigorously and quickly.
What are the components of a hydroponic system?
To maintain a well-functioning hydroponic system, you need to become familiar with several components that keep it operating efficiently.
Growing medium
Hydroponic plants are often grown in inert media that support the plant's weight and anchor its root structure. The growing medium is a substitute for soil, but it does not nourish the plant on its own. Instead, this porous medium retains moisture and nutrients from the nutrient solution and then delivers them to the plant. Many growing media are pH-neutral, so they do not disrupt the balance of the nutrient solution. There are many different media to choose from, and the particular plant and hydroponic system will determine which is best suited to your project. Hydroponic growing media are widely available both online and at local nurseries and garden centres.
Air stones and air pumps
Plants submerged in water can quickly drown if the water is not sufficiently oxygenated. Air stones disperse small bubbles of dissolved oxygen throughout the nutrient-solution reservoir. These bubbles also help distribute the dissolved nutrients evenly throughout the solution. Air stones do not generate oxygen by themselves. They must be connected to an external air pump with opaque, food-grade plastic tubing; the opacity helps prevent algae growth. Air stones and air pumps are popular aquarium components and can easily be purchased at pet shops.
Net pots
Net pots are specially designed for hydroponic plants. The mesh material allows roots to grow out through the sides and bottom of the pot, providing greater exposure to oxygen and nutrients. Net pots also provide better drainage than traditional clay or plastic pots.
What are the six types of hydroponic systems?
There are hundreds of hydroponic methods, but all are variations or combinations of six basic hydroponic systems.
1. Deep water culture systems
Deep water culture hydroponic systems are simply plants suspended in aerated water. Deep water culture systems, also known as a DWC system, are among the easiest and most popular hydroponic methods on the market. A DWC system suspends net pots containing plants above a deep reservoir of oxygen-rich nutrient solution. The plants' roots are submerged in the solution, giving them constant access to nutrients, water, and oxygen. Some consider deep water culture the purest form of hydroponics.
Because the root system is constantly in water, properly oxygenating the water is vital to the plant's survival. If the plant's roots are not supplied with enough oxygen, it will drown in the solution. Add an air stone connected to an air pump at the bottom of the reservoir to oxygenate the entire system. The bubbles from the air stone will also help circulate the nutrient solution.
It is very easy to assemble a deep water culture system at home without expensive hydroponic equipment. You can use a clean bucket or an old aquarium to hold the solution and place a floating surface such as polystyrene on top to support the net pots. In DWC systems, only the plants' roots should be submerged in the solution. No part of the stem or foliage should be under water. You can even leave about one and a half centimetres of the roots above the waterline. The air-stone bubbles will break at the surface and splash the exposed roots, so they will not be at risk of drying out.
What are the advantages of deep water culture systems?
Low maintenance: Once a deep water culture system has been set up, it requires very little maintenance. Simply top up the nutrient solution when necessary and make sure your pump is supplying oxygen to the air stone. The nutrient solution generally needs to be replenished only every 2–3 weeks, although this depends on the size of your plants.
What are the disadvantages of deep water culture systems?
Limitations: Deep water culture systems are well suited to growing herbs and lettuce, but struggle with larger, slow-growing plants. Deep water culture systems are not ideal for everything that flowers. With some extra work, however, you can grow plants such as tomatoes, peppers, and courgettes in a DWC system.
Temperature control: It is important that the temperature of the water solution does not exceed 20°C or fall below 15.5°C. The water in a DWC system is static and does not circulate, so temperature can be more difficult to regulate.
2. Wick systems
In a wick system, plants are placed in a growing medium on a tray positioned above a reservoir. This reservoir contains a water-based solution with dissolved nutrients. Wicks run from the reservoir into the growing medium. Water and nutrients travel up the wick and saturate the growing medium around the plants' root systems. The wicks can be made from ordinary materials such as rope, string, or felt. Wick systems are the simplest form of hydroponics. They are passive hydroponic systems, meaning that they require no mechanical parts such as pumps to operate. This makes them ideal in situations where electricity is unreliable or unavailable.
Wick systems work through a process called capillary action. The wick absorbs the water in which it is immersed like a sponge and transfers the nutrient solution when it comes into contact with the porous growing medium. Wick-system hydroponics works only with a growing medium capable of facilitating the transfer of nutrients and water. Coconut coir, made from the outer husks of coconuts, retains moisture exceptionally well and has the added advantage of being pH-neutral. Perlite is also pH-neutral and extremely porous, making it ideal for wick systems. Vermiculite is likewise highly porous and also has a high cation-exchange capacity. This means it can store nutrients for later use. These three growing media are best suited to hydroponic wick systems.
Wick systems operate considerably more slowly than other hydroponic systems, which limits what can practically be grown in them. Make sure that each plant in the growing tray has at least one wick running from the reservoir. These wicks should be positioned close to the plant's root system. Although wick systems can function without aeration, many people choose to add an air stone and air pump to the reservoir. This supplies the hydroponic system with additional oxygen.
What are the advantages of a wick system?
Simplicity: Anyone can set up a wick system, and it requires little attention once it is running. The wicks continuously supply your plants with water, so there is no risk of them drying out. Plants such as lettuce will also thrive in a wick system, providing an excellent return on your investment.
Efficient use of space: Wick systems are unobtrusive and can be installed anywhere because they do not require electricity. This is an ideal system for teachers, beginners, or anyone interested in hydroponics.
What are the disadvantages of a wick system?
Limitations: Lettuce and herbs such as rosemary, mint, and basil grow quickly and do not require large amounts of water. Tomatoes, on the other hand, will struggle in a wick system because of their high nutrient and water requirements. Other plants cannot thrive in a constantly moist environment. Root vegetables such as carrots and turnips will not develop successfully in a wick system.
Susceptible to rot: A hydroponic wick system is always damp and wet. This creates a risk of fungal outbreaks and rot in the organic growing medium and on plant roots.
3. Nutrient film technique systems
Nutrient film technique (NFT) systems suspend plants above a stream of continuously flowing nutrient solution that washes over the tips of their root systems. The channels holding the plants are tilted, allowing water to flow down the length of the growing tray before draining into the reservoir below. The water in the reservoir is then aerated with air stones. A submersible pump sends the nutrient-rich water from the reservoir back to the top of the channel. The nutrient film technique is a recirculating hydroponic system.
Unlike deep water culture hydroponics, the roots of plants in an NFT system are not submerged in water. Instead, the stream, or "film", passes only over the tips of their roots. The root tips draw moisture up into the plant, while the exposed root system has ample access to oxygen. The bottoms of the channels are grooved so that the shallow film passes easily over the root tips. This also prevents water from pooling or becoming trapped around the root system.
Although nutrient film technique systems continuously recycle water, it is wise to drain the reservoir and replenish the nutrient solution every week. This ensures that your plants receive enough nourishment. NFT channels must be set at a gentle angle. If the slope is too steep, the water will rush down the channel without feeding the plants properly. If too much water is pumped through the channel, the system will overflow and the plants may drown. NFT hydroponics is a popular commercial system because each channel can support several plants and the system is easy to scale for mass production. Nutrient film technique systems are best suited to lightweight plants such as mustard greens, kale, lettuce, and spinach, as well as fruits such as strawberries. Heavier fruiting plants such as tomatoes and cucumbers require trellises to support their additional weight.
What are the advantages of a nutrient film technique system?
Low consumption: Because NFT hydroponics recirculates water, it does not require large quantities of water or nutrients to operate. The constant flow also makes it difficult for salts to accumulate on plant roots. Nutrient film technique systems do not require a growing medium either, saving you the cost of buying media and the inconvenience of replacing them.
Modular design: Nutrient film systems are ideal for large-scale and commercial operations. Once you have established a functioning channel, it is very easy to expand. You can fill your greenhouse with multiple channels supporting different crops. It is a good idea to supply each channel from a separate reservoir. That way, if a pump fails or a disease spreads through the water, you will not lose your entire crop.
What are the disadvantages of a nutrient film technique system?
Pump failure: If the pump fails and the channel stops circulating the nutrient film, your plants will dry out. Your entire crop can die within a few hours if it is not supplied with water. Maintaining an NFT hydroponic system requires vigilance. You will need to monitor the operation of your pump carefully.
Overcrowding: If plants are spaced too closely or root growth becomes too vigorous, the channel can become clogged. If roots block the channel, water will be unable to flow and your plants will starve. This is especially true for plants at the lower end of the channel. If the plants at the end ever appear to be underperforming compared with the rest of the channel, consider removing some plants or switching to a smaller unit.
4. Ebb and flow systems
Ebb and flow hydroponics works by flooding the growing bed with nutrient solution from a reservoir below. The submersible pump in the reservoir is fitted with a timer. When the timer starts, the pump fills the growing bed with water and nutrients. When the timer stops, gravity slowly drains the water from the bed back into the reservoir. The system has an overflow tube to ensure that flooding does not rise above a certain level and damage the plants' stems and fruit. Unlike the previously mentioned systems, plants in an ebb and flow system are not constantly exposed to water. While the bed is flooded, plants absorb the nutrient solution through their root systems. When the water drains away and the bed empties, the roots dry out. The dry roots are then oxygenated during the interval before the next flood. The duration of the interval between floods is determined by the size of the bed and the size of the plants.
Ebb and flow systems, also called flood and drain systems, are among the most popular hydroponic growing methods. The abundance of oxygen and nutrients supplied to the plants encourages rapid, vigorous growth. An ebb and flow system is highly adaptable and versatile. The growing bed can be filled with an assortment of net pots and a variety of fruits and vegetables. Perhaps more than any other hydroponic system, ebb and flow allows you to experiment with plants and growing media.
Ebb and flow systems can accommodate almost any kind of plant. Your main limitation is the size and depth of your growing tray. Root vegetables will require a much deeper bed than lettuce or strawberries. Tomatoes, peas, beans, cucumbers, carrots, and peppers are popular crops grown in ebb and flow systems. You can even attach trellises directly to the growing bed. Growstones and expanded clay pebbles, also called hydroton, are among the most popular growing media for ebb and flow hydroponics. They can be cleaned and reused, are lightweight, and drain well even though they retain moisture. This is an important quality in ebb and flow systems.
What are the advantages of an ebb and flow system?
Versatility: With an ebb and flow system, you can grow much larger plants than in most other hydroponic systems. Fruits, flowers, and vegetables respond very well to ebb and flow hydroponics. If you provide your plants with a suitably sized bed and the right nutrition, you will enjoy an abundant harvest.
DIY: There are hundreds of ways to build your own ebb and flow hydroponic system at home. A visit to a hardware shop and pet shop will provide all the supplies you need to build one. Although they are more expensive to set up than other DIY systems such as wick and deep water culture systems, ebb and flow systems support a far broader range of plant species.
What are the disadvantages of an ebb and flow system?
Pump failure: As with any hydroponic system that relies on a pump, your plants will die if the pump stops working. You must monitor your ebb and flow system to ensure that its operation does not endanger your plants' health. If water flows in and out too quickly, your plants will not receive enough water and nutrients.
Rot and disease: Sanitation and maintenance are essential for an ebb and flow system. If the bed does not drain properly, root diseases and rot may develop. A dirty ebb and flow system can grow mould and attract insects. If you neglect cleanliness, your crop will suffer. In addition, some plants do not respond well to the rapid change in pH caused by extreme flooding and draining.
5. Drip systems
In a hydroponic drip system, an aerated, nutrient-rich reservoir pumps solution through a network of tubes to individual plants. This solution drips slowly into the growing medium around the root system, keeping the plants moist and well nourished. Drip systems are the most popular and widespread hydroponic method, especially among commercial growers. They can serve individual plants or massive irrigation operations.
Hydroponic drip systems have two configurations: recovery and non-recovery. In recovery systems, which are more popular among smaller home growers, excess water drains from the growing bed back into the reservoir to be recirculated during the next drip cycle. In non-recovery systems, excess water drains from the growing medium and runs to waste. This method is more popular among commercial growers. Although non-recovery drip systems may sound wasteful, large growers are very conservative with their water use. These drip systems are designed to deliver exactly the amount of solution needed to keep the growing medium around the plant moist. Non-recovery drip systems use sophisticated timers and feeding schedules to minimise waste.
If you grow plants with a recovery drip system, you need to account for changes in the pH of the nutrient solution. This applies to any system in which runoff circulates back into the reservoir. Plants deplete the nutrients in the solution and alter its pH balance, so the grower must monitor and adjust the solution reservoir more often than with a non-recovery system. Growing media can also become oversaturated with nutrients and will therefore need to be flushed and replaced periodically.
What are the advantages of a drip system?
Wide choice of plants: A drip system can support much larger plants than most other hydroponic systems. This is one reason why it is so attractive to commercial growers. Melons, pumpkins, onions, and courgettes can be adequately supported by a properly sized drip system. Drip systems contain larger quantities of growing medium than other systems, enabling them to support these plants' larger root systems. Drip systems work best with slow-draining media such as rockwool, coconut coir, and peat moss.
Scale: Drip systems can easily support large-scale hydroponic operations. If a grower wants to add more plants, new tubes can be connected to the reservoir to carry solution to the new vegetation. New crops can be introduced into an existing drip system by adding extra reservoirs with different timer schedules tailored to the needs of the new plants. This is another factor that makes drip systems popular in commercial hydroponics.
What are the disadvantages of a drip system?
Maintenance: Growing plants at home with a non-recovery drip system requires considerable maintenance. You will need to monitor the solution's pH and nutrient levels constantly, draining and replacing it when necessary. The lines in recovery systems can also become clogged with debris and plant matter, so you will need to wash and flush the delivery lines regularly.
Complexity: Drip systems can easily become complex and elaborate undertakings. This matters less in professional hydroponics, but it is not the most suitable system for home growers. There are much simpler systems, such as ebb and flow, that are better suited to home hydroponics.
6. Aeroponics
Aeroponic systems suspend plants in the air and expose their bare roots to a nutrient-rich mist. Aeroponic systems are enclosed structures, such as cubes or towers, that can hold multiple plants at once. Water and nutrients are stored in a reservoir and then pumped to a nozzle, which atomises the solution and distributes it as a fine mist. The mist is usually released from the top of the tower so that it can cascade down through the chamber. Some aeroponic systems continuously mist the plant roots, much like NFT systems expose roots to the nutrient film at all times. Others function more like an ebb and flow system, spraying the roots with mist at set intervals. Aeroponic plants do not need a substrate medium to survive. The roots' constant exposure to air allows them to absorb oxygen and grow at an accelerated rate.
Aeroponic systems use less water than any other form of hydroponics. In fact, growing a crop aeroponically requires 95% less water than growing it in an irrigated field. Their vertical structure is designed to occupy minimal space and allows multiple towers to be placed in one location. Aeroponics can produce large yields even in confined spaces. Moreover, because of their maximum exposure to oxygen, aeroponic plants grow faster than other hydroponically grown plants.
Aeroponics makes year-round harvesting easy. Vining and nightshade plants such as tomatoes, peppers, and aubergines do well in an aeroponic environment. Lettuce, baby greens, herbs, watermelons, strawberries, and ginger also thrive. Fruit trees, however, are too large and heavy to grow aeroponically, while underground plants with extensive root systems, such as carrots and potatoes, cannot be grown this way.
What are the advantages of an aeroponic system?
Abundant oxygen: The abundance of oxygen absorbed by the bare roots accelerates plant growth. Aeroponics is not only the most environmentally friendly hydroponic system, but also one of the most efficient. Aeroponic systems are versatile and adaptable, reliably producing high-quality results.
Mobility: Aeroponic towers and trays can easily be moved from one place to another without interrupting plant growth. During transport, you will need to mist the roots by hand to prevent them from drying out. Aeroponic systems are also designed to be ergonomic and make maximum use of space. Aeroponics allows you to grow plants at a higher density than other hydroponic systems.
What are the disadvantages of an aeroponic system?
Expensive: An aeroponic system has a higher initial cost than other hydroponic systems. Building a fully functional system with reservoirs, timers, and pumps can cost thousands of dollars. It is possible to build a DIY aeroponic system for much less, but this is a far more difficult undertaking than building your own deep water culture or wick system.
Maintenance: Aeroponic systems maintain a delicate balance, and if that balance is disrupted, the consequences for your plants are catastrophic. If your timer fails to activate or the pump breaks down, you risk losing your entire crop unless you mist the roots by hand. You will need to clean the root chamber regularly to prevent root diseases from developing. Overall, aeroponic systems require more technical expertise to operate successfully than other systems.
Reverse osmosis and hydroponics
The revitalising power of water lies at the heart of hydroponics. Water floods your hydroponic garden with nutrients, bringing the plants to life and encouraging their vigorous growth. If you are truly invested in the health of your plants, you must also care about the purity of the water that sustains them. Unfortunately, most water is full of contaminants. Municipal water suppliers disinfect water reserves with chlorine. According to the United States Geological Survey, 85% of water in the United States is hard, meaning that it contains elevated levels of calcium and magnesium. Industrial spills, agricultural runoff, and landfill waste can cause chemicals and volatile organic compounds (VOCs) to leach into groundwater.
Reverse osmosis, also called RO, removes 98% of all impurities from water by passing it through a semipermeable membrane. Reverse osmosis removes heavy metals, salts, bacteria, and total dissolved solids (TDS) from water. The result is water of remarkable purity. Using reverse-osmosis water for hydroponics ensures that your plants take up only the nutrients you want them to receive. Most commercial hydroponic operations use RO water to sustain their crops. Just as hydroponics shows that there is a better way to grow plants, reverse osmosis shows that there is a better way to support that growth.
Why should I use RO water for hydroponics?
Reverse-osmosis water allows you to start with pure water and add precise levels of nutrients, boosters, and pH adjusters. From this neutral base, you can create the ideal nutrient solution. For example, if you live in a hard-water area, your water will already contain high levels of calcium. Many hydroponic nutrient blends contain calcium because it promotes plant growth. Adding a calcium-rich solution to hard water, however, will create a nutrient imbalance. It is also much more difficult to measure nutrient levels in water with a high TDS level. Most manufacturers' instructions for nutrient solutions are based on RO water. So, if you are trying to bring your water to 800ppm of nutrients when it already has a TDS of 200ppm, you will have to estimate. The results will inevitably be inaccurate. Reverse-osmosis water also has a lower pH. Plants prefer acidic water, and using reverse-osmosis water to hydrate your crops will reduce the amount of pH adjustment you need to perform as a grower.
Controlling the nutrient balance and pH level of the water is integral to the success of your hydroponic operation. If your plants do not receive the right nutrition, it does not matter how well your hydroponic system works. A reverse-osmosis system ensures that your plants absorb only the appropriate nutrients, dissolved in water of the highest purity.
