Types of hydroponic systems
Hydroponic farming systems incorporate different soilless farming techniques to maximize production while saving on costs. There are six different hydroponic farming systems.
This is the most commonly used hydroponic system because of its simple and easily modifiable operation. The main operating principles are simple making easy to use. Vital plant nutrients are dissolved in a water tank which becomes the nutrient reservoir which is kept away from plants. The nutrient solution is then pumped through a network of drip irrigation pipes to individual plants.
The pump can be controlled by a timer – bypassing manual irrigation-hence making it possible to have a regular and timed irrigation of the plants. When an emitter is attached at the end of each irrigation pipe, you can control the timing and amount of nutrients to each plant. This means you can plant a range of crops on the same system.
There are two subtypes in the drip hydroponic systems:
- The recovery drip hydroponic system
- In recovery drip systems, there’s a provision for recycling excess nutrients. The excess nutrient solution drains back into the nutrient reservoir making the system for efficient. Recovery drip system requires regular inspection as concentrations of nutrients diminish over time as they are taken up by crops.
- Non-recovery drip hydroponic system.
- Non-recovery drip system does not recycle excess nutrient solution. This type requires less maintenance as ph and nutrient levels remain constant. Non-recovery drip system also minimizes disease spread throughout different plants.
Ebb and flow hydroponic system is also a popular hydroponic system due to its relative simplicity in setting up and operating. Just like the drip hydroponic system, flood and drain system uses a reservoir tank full of nutrient solution. The nutrient solution is pumped and flooded on the growing tray. After flooding, the pumped goes off and the solution in the growing tray trickles back into the nutrient reservoir.
A timer in the pump is set to activate the pump, periodically flooding the crops on the growing tray. The timer can be set to come on at different times depending on the type and size of plants, temperature and humidity and the type of growing medium used. Some growing medium such as gravel and perlite don’t hold water for long hence may need more frequent flooding than in other water holding media such as rock wool, vermiculite, and coconut fiber.
Since the runoff filters back into the reservoir, the hydroponic system is very low in maintenance and self-sufficient. On the downside, the nutrient solution in the reservoir tank needs a frequent inspection for optimal nutrient, oxygen, and ph levels.
This is the most basic type of hydroponic growing and is widely used in classroom instructional settings. This system uses a reservoir to hold the nutrient solution which is wicked up to the growing medium by capillary action. In this system, it’s important to use a good wicking (water sucking and holding) growing media such as vermiculite, rock wool, perlite, or coco coir.
In the wick system, the most critical component is the wick. For an efficient system, you need a good absorbent wick for optimal delivery of nutrients to the plants. The common materials used in the wick systems include propylene felt strips, fibrous rope, tiki torch wicks, rayon rope, wool felt, polyurethane yarn, nylon rope, cotton rope, or strips of fabric from old blankets.
The major downside with this system is that it doesn’t work for larger plants that require larger amounts of the nutrient solution since the wick can’t keep up with the delivery. The other con with the system is that it requires frequent flushing since excess nutrients might build up to toxic levels around the roots.
This is the oldest type of hydroponics and has been widely used for instructional purposes because of its technical simplicity. In hydroponic water culture systems, plants are suspended directly into the reservoir tank containing the nutrient solution. While the plants’ leaves are suspended above the floating Styrofoam, the roots are submerged into the nutrient solution.
Since the nutrient solution is stagnant in the reservoir, a pump is required to pump oxygen into the solution hence maintaining optimal oxygen levels.
There are four techniques used for aeration in this system:
- Air bubbles: An aquarium air pump and air stones are used to introduce air bubbles into the nutrient solution. The airstones are made of porous rock like material with the small pores creating many individual air bubbles which rise to the top of the nutrient solution near the roots.
- Falling water: In this version, falling water splashes hence incorporating oxygen. The higher the fall or the larger the volume of water, the bigger the splash which means more oxygen is incorporated and provided to the growing crops. This method of aeration is commonly used in commercial water culture where large amounts of water are used.
- Circulating water culture system: This is a variation of water culture system works on the same principle as flood and drain system only that the nutrient solution is never drained. Circulating water culture system allows utilization of falling water as an aeration source.
- Deep water culture (DWC): This is a variation of water culture system with the only difference being the depth of the nutrient solution. In true DWC, the nutrient solution depth is 8 to 10 inches deep. The depth of the solution is mostly determined by the size of the plant’s roots, nutrient and water requirement, or the type of container used.
Although water culture system is quite technically simple, it can be limited in the range of crops that can grow in this system. Since the roots are submerged in the nutrient solution, some plants die off due to excess nutrients and only water-loving plants such as lettuce do well in this system.
Although this system is popular with many hydroponic growers, it is only suited for growing quick-growing plants such as different types of green vegetables such as lettuce, baby greens, and other types of herbs.
In NFT system, the nutrient solution is continuously pumped into the growing table or pipe which gently slopes to allow a gentle flow of the thin nutrient film which collects and drains back into the reservoir. The plant’s roots are suspended in the space in the growing table or pipe. The flowing nutrient solution passes beneath the roots dampening and giving them an opportunity to absorb dissolved nutrients and water.
This system allows a continuous supply of nutrient solution to the growing plants hence eliminates the need for a timer and thus needs less attention in controlling the system.
In NFT system, the flow rate of the nutrient solution and the slope gradient of the growing table or growing tubes are major factors on nutrient delivery and overall efficiency of the system. The recommended slope of the growing table is 1:30 to 1:40 ratio, that means 1 inch in vertical drop for every 30 to 40 inches horizontal length. It’s recommended that in designing the system, the slope should be adjustable while plants are growing so as to keep up with the growing roots and avoid stagnation.
The recommended flow rate in NFT system is typically 1-2 liters per minute for each growing tube. The flow rate should be adjustable as younger delicate plants require lower flow rate compared to bigger maturing crops. Flow rates (higher or lower) are usually associated with nutrient deficiencies.
Nutrient film technique is highly associated with power outages hence regular pump and electric maintenance is essential to avoid system failures where the roots may dry out rapidly.
Although it is the most technical hydroponic system, aeroponic systems have been slated as the solution to future food shortages as it utilizes the least amount of water.
In this system, just like the NFT system, the plants’ roots are suspended in the air with their roots hanging in the air. The nutrient solution is pumped from the nutrient solution reservoir to high-pressure pump which is then sprayed as mist over the hanging roots. This system ensures maximum oxygen availability to the roots. Because the misting provides less amount of nutrients than in other systems hence the spraying takes place more frequently.
Due to the frequent circulation and spraying, the nutrient solution in this system is the most oxygenated resulting to faster growth and maturity rates of crops in the hydroponic aeroponic farming system.
This technology is looking promising for future food production because the system offers the possibility of growing crops vertically thereby maximizing production on a small area.
The major factor affecting aeroponic growing system is the size of the droplets. Roots sprayed with fine small droplets grow much faster and with larger surface area for absorption of nutrients than roots sprayed with large water droplets like in sprinkler heads.
There are three subtypes of aeroponic growing system categorized according to the water droplet size.
- Low-pressure aeroponic system (soakaponics): Although they aren’t the most efficient of aeroponics systems- because of large droplets-they are the most popular aeroponic systems because of their low cost and don’t require much in terms of special equipment. This system is usually uneconomical in large-scale growing.
- High-pressure aeroponic systems (true aeroponics): Although high-pressure systems are expensive and technically complicated, they are the most efficient aeroponic systems. In these systems, the nutrient solution is highly pressurized (60-90 psi) to atomize the solution into a fine mist with very small droplet size. In high-pressure systems, the roots get maximum oxygen and nutrients resulting in faster crop growth and maturity.
- Ultrasonic foggers: Ultrasonic foggers are used to generate mist. These foggers are usually used in creating visual displays on ponds or stage. Although they are capable of producing mist, there is very little actual moisture in the fog. The other downside with ultrasonic foggers is that the fog seems to drop to the bottom making it difficult to ensure the roots are covered by the mist at all times.