Deep Water Culture System

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Deep Water Culture is not often discussed on many general growing websites as it’s not suitable for growing all types of plants,  it’s quite specific to what you can actually grow using this type of growing method but it is interesting and useful to understand the basics. Unlike other Hydroponic growing methods this type of growing system does not utilise any type of recirculation of the nutrients to help the plants grow. Instead of using pumps or gravity to feed the plants this system uses a tank full of a pre mixed nutrient solution and the plants simply float on the surface with the roots submerged in the actual solution using a raft of polystyrene and little plastic baskets to make it float. An air stone is often used to assist in oxygen delivery to the roots and to help keep the solution from becoming stagnant.

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The actual growing medium used in deep water hydroponics is a little different too, you can’t use soil or cocoa or any heavy medium, even rockwool is not ideal for this application. Most growers use clay pebbles for this as they are light and easy to work with. This method of growing is usually reserved for the likes of lettuce as it is easy to scale up commercially and lettuce is a fast growing plant especially when grown hydroponically and it is not an heavy plant when ready for harvesting.

How it works

The chosen plants, in this case lettuce, are usually grown from seed; the seeds will be propagated in a little plastic basket until they are established and ready to be grown on. The basket is then placed into the polystyrene raft ready to go into the nutrient solution and be grown under natural lights via poly tunnels.

The nutrient solution is simply housed in a tank or reservoir, commercial growers will have huge tanks with many rafts floating in a kind of production line where the fully grown lettuce are removed from one end as the newly planted ones are added to the other. An air stone is a vital component in this system as it keeps the solution oxygenated and stops it from becoming stagnant. Stagnant nutrient solution can harbour all sorts of unwanted enzymes and bacteria that can be harmful to plants.

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As with all hydroponics systems it is beneficial to change the solution periodically to refresh it and ensure good clean growth, the used nutrients from the tank will normally be used to feed other plants in pots or directly in the ground that don’t require recirculation, the solution will be full of beneficial nutrients so it would be a shame just to waste it. Because of the way the way water culture or deep water hydroponics works it would be impossible to grow most plants using this method, apart from the fact that many plants will be simply too heavy to float n polystyrene there is also no definite way to support the plant through its growth cycle which is why it’s mainly used for small light plants such as lettuce.

The video below will show you the basic set up of a deep water culture hydroponics system. The equipment used will vary but the basic principles are the same.

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