Substrates for hydroponics

Substrates for hydroponics

The optimal supply of nutrients and oxygen to the roots is the main reason for faster and more vigorous plant growth in hydroponic systems compared to cultivation in soil. In Aeroponic cultivation systems, substrates are not used. They are highly efficient but also require optimal monitoring to avoid failures. In most cases, such as e.g. NFT, ebb and flood, or DWC, substrates are used.

Properties of substrates

There is a choice of inorganic or organic substrates with very favorable properties for plant growth:

  • higher porosity compared to soil
  • easily rootable, so that plants use little energy
  • easy access of nutrient solution to the roots
  • easy to drain, so that oxygen can penetrate from the air

Below are a few of the common substrate materials briefly described. With these we have carried out our own experiments. They differ in specific gravity, water absorption, drainability, influence e.g. on the pH value of the nutrient solution, the available grain size and the cost. We do not want to go into all the details, just give an overview.

Expanded clay balls

Clay balls are fired at high temperatures. This creates stable, porous balls that can partially float. The water storage is low but the air content of the bed and the drainability are very high. pH neutral types should be used. Clay balls are easy to use and can be rinsed and reused frequently.

Rock wool substrate

Produced from minerals at high temperatures, very light, with high porosity. Very cheap and therefore widely used. Disadvantages are fiber dusts during handling, uneven moisture in the substrate, no optimal supply of oxygen.

Lava stone, pumice substrate

It is a natural, lightweight, porous substrate material of volcanic origin. They differ in silicate content, purity and porosity. As a substrate, it is inert with low water storage capacity, but ensures good ventilation. The robustness is lower compared to expanded clay. Often they are used in substrate mixtures.

Perlite substrate

Perlite is also of volcanic origin, has been treated at high temperature and is therefore highly porous. Unfortunately, the disadvantage is that perlite floats and is less suitable as a substrate. When plants are grown from seeds, perlite has advantages, as it can be easily rinsed off the roots.

Ceramic substrate

Sintered, porous ceramic substrate has good water storage capacity, high air content in the bed, is well drainable and very well suited when microorganisms are desired in the system, e.g. in organic fertilizers. They are well populated. The ceramic substrates should not be too sharp, so as not to damage the delicate roots.

Plastic sponge substrate

Organic, but synthetically produced are plastic sponges. They are not compostable. Their advantage is the very low price and the large pore volume. They have a good water storage capacity, but do not condense when watering and work properly.

Eazy Plug® substrate

An easy-to-use, stable and clean substrate material is Eazy Plug. It consists of a special blend of organic materials. Eazy Plugs are sturdy, do not decompose, but are compostable. They have a very favorable water to air ratio, are equipped with a basic fertilizer and have a favorable pH. They are suitable for the most diverse hyproponic systems.

Peat substrate

Peat is an organic sediment that has developed extremely slowly in moors. Peat has a high spring and water storage capacity. The latter can lead to compaction when irrigated. Since peat is also very sour, it is only used in mixtures. Coconut and peat pots are often used for seed cultivation. Unfortunately, contamination of the hydroponic system can not be completely avoided.

Coconut fiber substrate

The coconut substrate is obtained as a by-product in the processing of coconut shells. Short fibers are dried and pressed into shaped bodies. This makes it very compact for transportation. Addition of water produces about 14 liters of coconut substrate from 1 kg of pressed material. A disadvantage is the often high and fluctuating salinity, which must be considered in hydroponic cultivation. As a substrate, it has been proven in many applications.