Types of Hydroponics

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The types of hydroponics systems

Kratky Method

The Kratky Method uses a static nutrient solution, similar to the Wick System and is one of the most basic forms of hydroponics. Plants are grown in containers such as buckets or Mason jars, and the simplicity of the grow means many setups are homemade with limited equipment. No electricity is used and so no air pump is fitted. The plant's roots can be suspended slightly above the nutrient solution for access to an oxygen supply.

A hole is cut for each plant into the shelf or container lid sitting above the waterline and there can be as many plants in the setup as the reservoir will allow as

Homemade nutrient solution cultures are created with plastic tubs or glass jars. If glass jars are used, it’s important to block the light reaching the nutrient solution to minimise algal growth. Light blocking equipment can be as basic as kitchen foil or baking paper.

The benefit of growing with The Kratky Method is not having to add a fresh supply of nutrient solution at regular intervals - there's no harm in doing it, but the idea is that it's a low maintenance system. Alternatively, as with all systems, you can check the concentration of the nutrient supply with an electrical conductivity meter and pH meter.

As the volume of water decreases, air fills in the space. The exposed roots can then take in the additional oxygen they need as they grow larger. If you decide to add an airstone to guarantee optimal oxygen absorption, you're moving into the realms of a more advanced but more efficient system - The Deep Water Culture.

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Nutrient Film Technique

In the Nutrient Film Technique, NFT, a shallow stream of nutrient solution is passed across a thick bed of roots that develops. The upper side of the root bed is exposed to the air so plants receive sufficient oxygen for growth but, if necessary, extra oxygen supply can be added to the nutrient solution through air pumps that sit in the reservoir.

The concentration of the nutrient solution is adjusted in the reservoir and pumped up to a channel which sits on an incline. Gravity pulls the nutrient solution down and causes it to flow around and across the plant roots where it's absorbed. Once it reaches the bottom of the channel a drainage opening takes it back to the reservoir and it's recirculated again.

To maximise growth yield, the length and the incline of the slope, which dictates the flow rate, are precisely measured. Slopes with too much gradient will cause water to pool at certain points within the root mesh as it can’t pour through the gaps fast enough. At the other end of the spectrum, too shallower an incline will mean the roots near the beginning of the channel will have access to the majority of the nutrients, leaving nothing for those at the bottom. Optimal flow rates range from 0.5L/min to 2L/min - outside this may cause nutritional deficiencies for some plants. Similarly, if the length of the channel’s too long there may be nitrogen depletion. Thus, channel length shouldn’t exceed 10-15 meters unless an additional nutrient supply is being provided halfway down the track.

When done correctly, the NFT makes it easier to provide plants with their preferred concentrations of water, nutrients, and oxygen compared to other setups. The main disadvantage of this technique is pump failure. If there's no speedy resolution, the plants won't have access to the nutrients they need to survive and will quickly die.

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Passive Sub-irrigation

Passive sub-irrigation is also referred to as semi-hydroponics and uses chemically inactive, porous material to transport nutrient solution via capillary action. A reservoir holds the nutrient solution which is then sucked up through a very absorbent wick into the growing container housing the plants and inert potting material. The wick transfers the nutrient solution to the potting material by capillary action and eventually soaks the whole volume of the container.

The growing medium the plants sit in has many pockets and spaces between the grains that fill with air, and so a large amount of oxygen is available to the root system as well as letting them dry out enough to avoid root rot. Certain species of plant, such as orchids, have exposed roots in their natural environment and increased airspaces are beneficial for you getting big, juicy orchid flowers. It's important to note that increased humidity in the system from evaporation means plants preferring drier conditions are less suitable to grow here.

Passive sub-irrigation maintenance is relatively easy and cultivating a larger number of plants can be done at reduced with minimal work.

You need to read about the different type of potting material used in the Passive Sub-irrigation system. Some examples include perlite, vermiculite, and charcoal.

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Ebb And Flow

Also known as Flood and Drain, Ebb and Flow setups rely on a pumps flooding of the growing tray with nutrient solution and allowing it to drain out again into the reservoir. It’s a very reliable system and, although usually low in costs, can end up complicated in its design. A major disadvantage is relying entirely on a pump and, if this stops working, will cause your plants to die quickly without access nutrients.

Allowing gravity to naturally drain the nutrient solution away by placing the reservoir under the growth medium reduces the reliance on technology without compromising productivity, but you still have to pump it back into the grow tray regardless. Flooding lasts for a short period of time, approximately five to ten minutes, however, this method isn’t popular among commercial hydroponic farmers.

If not controlled properly, the Ebb and Flow system will lead to higher incidence of root disease seen and regular cleaning of the nutrient solution necessary. This is managed by draining the water after no longer than 30 minutes in the grow tray to allow sufficient oxygen to reach the roots and removing anaerobic conditions from the root system.

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Drip System

The Deep Water Culture is a system where plant roots are suspended into an oxygenated nutrient solution while the main plant sits above the reservoir. It's a highly oxygenated method and results in fast growth with high yield.

The Drip System is the same, the plants are suspended above the waterline and the roots sit in the oxygenated nutrient solution. The difference is, simultaneously, a water pump is spraying nutrient solution from the reservoir directly onto the exposed root system 24/7. This is where the name's derived.

During the first few weeks post-planting, the roots grow downwards to reach the nutrient solution. This method means the root system gets a constant supply of oxygenated nutrient solution and is intended to speed up the early growth phase. Once the plants have grown enough to reach the water level, they don’t really need any more assistance, and thus a standard deep water culture setup is sufficient.