Choosing the best substrate for hydroponic growing
The substrate - or growing medium - is the substance in which plants are sown and grown.
In hydroponic cultivation, although it is not a soil as such, it is the place where the root system of the plants will expand. The substrate itself does not contain any nutrients and - for this reason - is called an inert substrate. Because of this specific characteristic - which differentiates it from normal growing soil or potting compost - it becomes necessary to irrigate it, either continuously or at intervals, with nutrient solution.
It should be noted, however, that for many varieties of plants the use of a substrate is not necessary because they can be grown directly in the nutrient solution.
In hydroponic cultivation, the general approach is to use highly efficient substrates which can be recovered, either for use in several cultivation cycles or for recycling: for example, when they no longer perform their function, they can be inserted and reused in the industrial or construction market.
Here you will find all hydroponic substrates for sale online.
Which substrates are suitable for hydroponic growing? Here are the best
Rockwool Root Riot Peat Expanded Clay Perlite and Vermiculite
The best substrates for amateur and professional hydroponic cultivation are described below:
Rockwool and Grodan
Rockwool is a soft, very permeable material and therefore has a low water retention capacity while having a high capacity to circulate a lot of oxygen. This material is not biodegradable and is sold in cubes (Rockwool cubes) or slabs (Rockwool slabs). It is possible to use rockwool in various hydroponic growing techniques, such as bag culture, or in active drip hydroponic systems. More often than not in professional hydroponic cultivation, rockwool is used for germinating seeds in hydroponic seedbeds. Seeds can be sown in slabs or cubes of rockwool as long as it is placed in a container in the bottom of which one or two centimetres of nutrient solution remain constantly. This substrate is very convenient for moving newly hatched plants from the germination area to the growth area: just gently move the whole cube with the roots and place it directly into the hydroponic system. To re-use the rockwool, simply wash it with bleach or lysoform in a 4:1 ratio, i.e. four parts water to one part bleach or lysoform, then rinse and leave to dry.
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Root Riot Organic Cubes
Root Riot cubes are made of composted organic material. These cubes have a very spongy consistency and maintain the ideal oxygen/water ratio that plants need in hydroponic cultivation. This material is used in the same way as traditional rockwool and is suitable for both cuttings and germinating seeds.. Generally, biodegradable sponge cubes are pre-fertilised (slightly) to improve the success rate of seed germination and cuttings propagation.
Peat
Peat is a soft, fluffy organic substance that gets on very well with plant roots. It is often mixed with vermiculite, perlite (or agri-perlite) and sand. Peat for hydroponics should not be confused with peat for potting soil. The colour of dry peat used in hydroponic cultivation is light brown, that of compost is generally black. A shortcoming of peat in hydroponics is that it becomes impermeable to water when dry, so it is best to keep it moist even when not in use. A good way to do this is to put it in a tightly sealed plastic bag. To obtain a softer, more draining substrate it is advisable to follow one of the following formulas:
- 10 litres peat + 4 litres perlite
- 10 litres of peat + 4 litres of vermiculite
- 10 litres of peat + 4 litres of polystyrene foam in small pieces
Expanded Clay for Horticulture
Expanded clay is an inert, non-organic, fairly light material that is widely used in hydroponics because of its properties: the expanded clay balls do not fit together, leaving ample space for oxygen to accumulate. Expanded clay has very good water retention and can absorb 30% of water, as well as having formidable draining properties. It is reusable for many crops, sterilises easily and is recyclable. These qualities, combined with the fact that it is economically viable, have made it a perfect substrate for indoor hydroponic growing.
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Perlite and Vermiculite
Perlite - or Agriperlite - and vermiculite are inorganic and inert materials. They are often used to lighten more compact substrates in order to make them more airy and draining. In hydroponics they are sometimes used alone or combined with portions of sand. They are light materials, usually packaged in bags in the form of granules or balls.
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