The importance of hygiene and disinfectants in hydroponics
A brief introduction to hydroponic systems and disinfectants in hydroponics
Plant breeding with hydroponics (hydroponic growing and hydroponic gardens) is not a new invention. Ever since the rise of agriculture, humanity has endeavoured to grow crops and medicinal plants using the optimal amount of water, fertiliser and nutrients so as to increase the yield per cultivated area.
This undertaking can only succeed by linking the plants, substrate and water or fertiliser as closely as possible. Breeding plants in this fashion has its pitfalls, however. Close proximity and shared nutrient solutions enable plant diseases to spread rapidly.
What is hydroponics? How do hydrocultures work?
Hydroponic systems are hydrocultures where the plant is fixed in a substrate (rock wool, coir or expanded clay, rarely soil) in pots or brackets and supplied with water and hydroponics nutrients or fertiliser at regular intervals.
There are active and passive systems.
In passive hydroponics systems, the plant is “suspended” above a pool/pipe with a nutrient solution, which is drawn up to the roots through a wick (made from fibreglass, for example) or absorbent substrate.
Passive hydrocultures are slightly less effective than active hydroponic systems, but very straightforward and not dependent on controls, electricity, pumps and so forth. They are therefore less prone to mistakes and disruption than the active hydroponic systems.
In contrast, active hydroponics systems use pumps to transport the nutrient solution to the plant roots.
Active hydroponic systems include:
• Flood trays (ebb and flow systems)
• Dripping systems / top feed (tube-based drip irrigation)
• NFT nutrient film (liquid film)
• DWC (deep water culture) hydroculture
• Aeroponic systems (roots are kept suspended in air and sprayed)
Ebb and flow (flood trays) hydroculture
The hydroponics plants are placed in pots with a substrate in a low basin, the flood tray. The substrate supports the plants and serves as a temporary depot for the nutrient solution. At regular intervals, a pump floods the trays with nutrient solution from a tank, and drains surplus water back into the reservoir.
It is a very straightforward hydroponic technique, however flood systems have a tendency to become contaminated with pathogens very quickly. Biolfilm develops rapidly as a result of the large surface and liquid/air boundary. Bacteria and fungi flourish. Root rot caused by fungi (pythium) occurs frequently in untreated systems. This is why it is so important to use disinfectants in hydroponics.
Drip hydroculture
This type is found frequently in hydroponics and comes in many varieties. In the simplest version, plants are placed in pots with an expanded clay aggregate. Small tubes connect each plant to the branching irrigation system and allow individual dosing of water and hydroponics nutrients.
Depending on the hydroponics system and hydroponics plants, surplus nutrient solution is drained back into a reservoir. Problems can occur with this hydroponics system particularly when high temperatures cause water oxygen levels in the thin tubes to drop, promoting root rot. In addition, the tubes tend to scale and attract biofilms. This can lead to blockages and crop failure.
NFT hydroponics (nutrient film)
NFT hydroponic systems are classic recirculation systems and similar to ebb and flow hydrocultures. The plants are placed in pots in a slanted trough, and the nutrient solution / water runs as a thin film from one side to the other and back into the reservoir. The nutrient solution is used multiple times and can be continuously monitored in the reservoir, and supplemented with required substances and oxygenated.
It is critical to cover it with opaque foil to prevent algae growth. Without adding Sanosil disinfectants in hydroponics to the nutrient solution, it will frequently need to be replaced entirely, as it tends to be a breeding ground for pathogens.
DWC hydroponic deep water culture
The semi-active deep water hydroculture is a special case.
Pots with the substrate and hydroponics plants are suspended in tanks flooded with nutrient solution, preferably only to the point that the nutrient solution just touches the expanded clay aggregate. The nutrient solution is aerated and oxygenated. The expanded clay aggregate draws up the nutrient solution, allowing the roots to thrive. Soon, the roots extend beyond the pots and into the water.
As the plants grow, the level of nutrient solution decreases. This exposes the roots more to the air, enabling them to absorb additional oxygen. The system does not require irrigation pumps, however air pumps for oxygenating the nutrient solution are a must.
Potential problems with hydroponic systems
Because hydroponic hydrocultures are installed in greenhouses and can therefore be fully isolated from the environment, there are far fewer problems due to pests than in conventional fields.
However, there are other difficulties: the often warm temperatures in greenhouses and (especially when using drip) the many thin tubes cause the water to heat up quickly. This makes it more difficult to bind oxygen and CO2.
Biofilms are another problem. Slimy formations of algae, protozoans and fungi which form rapidly. These plaques can block parts of the irrigation system and cause crop failure. In addition, biofilms are an excellent reservoir for bacteria and fungi which can harm the root systems of the plants. The best way to fight the majority of these problems is to use disinfectants in hydroponics.
Disinfecting the water with disinfectants in hydroponics to prevent root rot and other diseases
Dosing disinfectants in the nutrient solution to stabilise bacterial growth in hydroponic systems is not a new idea, however most effective disinfectant for hydroponics is also toxic to the plants inhabiting the hydroculture. Oxidising disinfectants in hydroponics such as chlorine break down relatively quickly, precluding any long-term effect and therefore making them unsuitable for use in hydroponics systems.
This becomes even clearer with systems such as ozonisation and UV radiation. They keep acute pathogen growth in the reservoir in check, but have no effect whatsoever on the tubes.
In contrast, treatment with the Sanosil 2-component system does both. The oxidising hydrogen peroxide breaks down into water and oxygen without leaving a residue that is harmful to plants. Tiny concentrations of silver remain, which have a long-term preservative effect and support the action of the hydrogen peroxide.
Sanosil disinfectants in hydroponics S015 and Super 25 are therefore the first choice for nutrient solutions in hydroponics systems — particularly as they can also be used to disinfect surfaces and treat certain plant diseases.
