Hydroponic growing media or pure nutrient solution, which is better for hydroponics?

Hydroponics takes many forms: while some techniques require the use of special substrates, others allow plants to be grown solely in a nutrient solution. Are you interested in which of these methods is more advantageous for your plants? In the following article, we compare the advantages and disadvantages of both methods so that you can better decide which is best for your hydroponic cultivation.

Hydroponics is an innovative soilless growing method in which plants are fed with a nutrient-rich solution. In hydroponic cultivation, plants can grow either in an inert (chemically inactive) substrate or be placed in special hydroponic systems with roots freely immersed in a nutrient solution. Compared with growing in soil, hydroponics is somewhat more demanding for beginners to master, but it allows faster and more efficient plant cultivation.

Hydroponic growing media

Just like soil, hydroponic growing substrates serve as support for root anchorage and retain water (nutrient solution), which plants absorb. Unlike soil, however, most hydroponic media are made from inorganic materials and do not contain plant nutrients. The most common substrates for hydroponics include:

• Rockwool

Mineral wool made from basalt rock is one of the most widely used hydroponic media. Rockwool can be easily shaped into cubes or mats, which makes it a versatile growing medium for a wide range of hydroponic systems, and you can use it not only for growing itself, but also for germination or propagation. Mineral wool has excellent retention properties and dries evenly, which makes rockwool easy to use with automatic irrigation systems (drip, run-to-waste, spinners, flood trays). Rockwool is not suitable for growing in pots or for hand watering.

• Coconut fibres

Hydroponic media made from coconut fibres and husks combine the advantages of inert substrates (rockwool, expanded clay, perlite) and soil mixes containing earth. They have better retention properties than soil while not being completely inorganic, and they allow beneficial microorganisms to grow. Coconut substrates are suitable for beginners and growers who want to use organic fertilisers in hydroponics. Coco can be used for growing in pots (plastic, fabric and Auto-Pot) with hand watering as well as in self-watering systems.

• Expanded clay

Expanded clay, also known as LECA, is a porous material made from clay heated to a high temperature. It takes the form of small pebbles, most often used in hydroponic systems (run-to-waste, DWC, NFT, ebb-and-flow) and in aeroponics as a medium for anchoring plants. Expanded clay dries out quickly and is therefore not suitable for growing in pots with hand watering.

• Perlite

Perlite is a growing substrate made by heating rock to a high temperature, which looks like a light white granulate. Like expanded clay, perlite retains a small amount of water and allows good access of air to the roots. Due to its fine structure, perlite easily clogs irrigation systems, and as a standalone hydroponic medium it can only be used when growing in flood trays (Dutch bucket).

Would you like to learn more about growing substrates? Read our Guide to Growing Substrates.

Advantages of growing in hydroponic substrates

• Support for the root system: Hydroponic media provide plants with sufficient support and are more suitable for large plants than NFT, DWC and other hydroponic systems.
• Water retention: Growing substrates maintain a stable level of moisture even with occasional watering and do not require a constant supply of nutrient solution.
• Aeration: Compared with soil, hydroponic media ensure better access of oxygen to the roots and reduce the risk of plants being affected by mould.
• Ease of use: Compared with fully hydroponic systems, substrate methods are less prone to faults and grower errors.

Soilless hydroponic systems

Some hydroponic systems do not require plants to be placed in a substrate, but allow the roots to be immersed directly in a nutrient solution. The main advantages of this method are that the roots have a constant supply of water, nutrients and oxygen. Plants therefore grow faster and the risk of soil pests multiplying is eliminated. On the other hand, “clean” hydroponics requires constant monitoring of nutrient content and pH of the nutrient solution and does not allow even the slightest mistake on the grower’s part. Commonly used soilless hydroponic systems include:

• NFT (Nutrient Film Technique)

In NFT hydroponic systems, the roots of the plant are placed in a slightly inclined channel or tray where a thin stream of water flows over them. Plants are usually placed in perforated hydroponic baskets in openings along the entire length of the channel. The nutrient solution flows into a reservoir from where it is pumped back to the top of the channel, creating a recirculation system. NFT systems are very efficient. They do not waste water or fertilisers and offer sufficient oxygenation of the nutrient solution, which prevents root rot. NFT is suitable for smaller plants with a shorter vegetative cycle, but perennials can also be grown in them.

• DWC (Deep Water Culture)

The older hydroponic technique abbreviated as DWC consists of immersing plants in a tank or bucket with an oxygenated solution. As with NFT, the plants are placed in perforated pots in an opening in the lid of the growing tank. Aeration of the nutrient solution in DWC is provided by a pump and an air stone. Compared with other fully hydroponic systems, DWC is a relatively simple and inexpensive option. On the other hand, this method carries a greater risk of poor oxygenation and root rot. DWC can be used both for growing plants with a short vegetative cycle and for perennials and shrubs.

• Kratky method

At first glance, this simple hydroponic technique developed by Bernard Kratky is characterised by growing plants in separate closed containers, where they are suspended in a nutrient solution while part of the roots remains exposed to air. As the plants grow and gradually draw down the nutrient solution, the level in the container drops, which stimulates the development of new roots in the plants. Although this is a very inexpensive hydroponic solution, the Kratky method is relatively demanding to master and not very efficient.

• Aeroponics

Aeroponic systems deserve their own category, but in a broader sense they can be included among other hydroponic techniques. In aeroponics, plant roots are suspended in the air and regularly misted with a fine nutrient solution spray. The advantage of aeroponics is the huge amount of oxygen the plants receive, which supports rapid development of the root system. On the other hand, aeroponics requires specialised equipment, and if it breaks down, plants have only a minimal chance of survival. A great use for aeroponics is in propagation units, where this method speeds up the formation of new roots by up to a week.

Advantages of growing in nutrient solution

• Rapid nutrient uptake: Plants with roots immersed in a nutrient solution have a constant supply of nutrients, resulting in faster growth and higher yields.
• Lower risk of pathogens: When growing in purely hydroponic systems, soil pests do not oc