Types of substrates

All fans of gardening and horticulture are familiar to a greater or lesser extent with the term substrate. Substrates are a vital element when growing any type of plant and, although there are universal substrates that tend to work well with most plants, there are a large number of types of substrates in gardening. Substrate mixtures have very different properties and are more suitable for different plants, so it is worth studying them in greater depth to be much more successful with our crops, whether they are orchards or ornamental plants.

What is the substrate for plants

When we talk about substrates for plants , we refer to the land that we use to grow them , either in a pot or in the ground, when we prepare and add the mixture ourselves.

The substrate will almost always have properties that are very different from those of natural soil, and it is always prepared seeking to provide the crop with an optimal growth and development medium, taking care of aspects such as water and moisture retention, the amount of organic matter present, the degree of compaction or the pH level.

Types of substrates according to their properties

When we talk about substrates according to their properties, we divide them into chemically inert and chemically active.

  • The chemically inert substrates are substrates that simply support the plant, not intervening at all in providing nutrients or fixing. When using these substrates, the nutrients must be provided separately.
  • The chemically active substrates also act as a support but also provide nutrients or retaining, storing and releasing excess when the plant needs.
Types of substrates - Types of substrates according to their properties

Types of substrates according to the materials

If we look at the origin of the component material, we differentiate organic substrates of minerals or inorganic substrates .

  • There are several types of organic substrates , which are those of natural origin such as peat, synthetic ones such as expanded polystyrene and by-products or residues that, once composted, are valid for use, such as sawdust, pruning remains, water treatment sludge, etc.
  • There are also different types of inorganic substrates , depending on whether they are of natural origin such as sand and gravel, processed such as perlite and expanded clay, or, again, waste such as blast furnace slag.

Types of natural substrates

These are some of the most used natural substrates :

Water

The substrate for hydroponics is, in many cases, simple water. All plants need water to survive, but in the right facilities this can also be used as a substrate. 

Sands

Sands have a medium water retention capacity and compact over time, although they are highly durable. Due to their ideal grain size, between 0.5 and 2mm, they are commonly mixed with peat moss to prepare potting substrates .

Gravels

The gravels have a diameter of between 5 mm and 15 mm. The gravels most used as a substrate for plants are pumice and quartz. The substrate made with pumice or pumice stone is also known as tepojal. 

Volcanic earth

When using untreated volcanic material, we find porous substrates with slightly acidic pH, which provides great aeration and low water retention. They are difficult to work with due to their heterogeneity.

Mobs

Product of natural decomposition of plants over a long time, mobs are classified as black and blonde . The latter are richer in organic matter and have better aeration and water retention capacity, which is why the two are often mixed.

Pine bark

Coming mostly from the wood industry, it is a substrate that is used raw or composted, the latter being preferable. The substrate of pine bark is lightweight with high porosity and aeration, which tends to slightly acid.

Coconut fiber

Coconut fiber is one of the most used substrates for seedlings, especially when it is combined with peat and organic matter is added. It is very light and must be washed with salts before use. 

Types of artificial substrates

The most used artificial substrates are the following:

Perlite

Siliceous volcanic rock subjected to temperatures between 1,000 and 1,200 ºC, perlite is a low-density substrate, with an enormous water retention capacity. It is of limited durability and neutral pH, and tends to mix with other substrates such as peat to improve its properties.

Rock wool

It is obtained by melting basalt, calcareous and coke coal at a temperature of more than 1,600 ºC. A homogeneous, inert and easy-to-handle material is obtained, which provides good aeration and water retention, but with an even more limited durability than perlite: it lasts around 3 years.

Vermiculite

Similar to perlite, vermiculite is finer-grained and is obtained by exfoliating micas at more than 800ºC. It has a great capacity for aeration and water retention, but it tends to compact over time.

Expanded clay

When clay-type nodules are treated above 100 ºC, we obtain these balls of between 2 mm and 10 mm in diameter, with a hard exterior and great aeration capacity. It retains little water and tends to mix with peat to improve substrate drainage.

Expanded polystyrene

It is a plastic cut into lumps of between 4 mm and 12 mm and white in color. It is of extraordinarily low density and provides very good aeration as well as low water holding capacity. It is added to compact substrates such as peat to improve its aeration.

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