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Hydroponics systems use substrates. A wide range of both familiar and new substrates are being produced and promoted. There are organic and inorganic types and naturally occurring and artificial types. Of the naturally occurring substrates, some are used in their natural form and some are processed. There are also a number based on recycled materials.
Some recycled media have proved to be phytotoxic to plants, due to toxic products among the source materials. An example is nursery potting mixes made from sewage sludge. Early batches of this medium had excessive levels of toxic elements and compensation of many million dollars was paid to growers whose plants died as a result.
The main medium used for hydroponics has been rockwool. Another medium used extensively is peat, although most of this is used in the nursery pot plant industry.
A much wider range of substrates are being used commercially. These include plastic foam, processed wood substrates, perlite, pumice, peat, coconut peat, and glasswool.
Different plant species are best grown with different support systems
Plants need air as well as water around the roots. They need a healthy root environment.
Plant roots do work and so consume oxygen which they must take
in from their local environment. A root environment devoid of
oxygen will damage/kill the plant. The roots of plants have mechanisms
for getting from the water in their vicinity the dissolved ions
of all the nutrients a plant needs. The plant can only obtain
the nutrients that are actually dissolved in water. Each mechanism
has its own different efficiency. This means that the optimum
nutrient solution is different from the level of ions inside the
plant root. Each plant variety have different performances and
so require their own optimized solution for optimum growth.
The differences between different media affecting plants are the
Small plants such as lettuce or herbs are best grown using aeroponic chamber (growing with a cloud) or NFT system (Nutrient Flow technique).
Bigger plants like tomatoes are best grown in a support media.
Media and systems are:
Reference: How to grow 86 different plants in hydroponics by John
Prepared by Trevor Croll,
42 Pearse Street, Keperra, Queensland Australia, 4054.
Phone 61 7 3855 1115