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What is the difference between seedling substrate and universal substrate?
The seedling substrate has a finer, sifted texture, with uniform granulometry so that young roots penetrate without resistance, a Specific pH (5,5–6,5) y low electrical conductivity (EC) to avoid salt stress. The universal substrate is designed for already developed plants, with more fertilization and coarser particles, so it can become compacted and too "strong" for sensitive seedlings. You can learn more about different types of substrate in our article on the universal substrate and its applications.
Does the seedling substrate contain fertilizer?
Yes, most professional models include one. gentle and balanced initial fertilization, enough to cover the first few weeks without adding external nutrients. This load is deliberately low to protect the radicle; later, after the pricking, the nutrition is increased. You can also read our article on how to make seedbeds suitable for children best practices for fertilizing seedbeds.
How long can the substrate be used once opened?
It is recommended to use it within a period of 6 to 12 months after opening, keeping it closed, in dry and shady placeOver time, it may lose structure, aeration, and microbiological activity; if it smells fermented or is caked, discard it for fine sowingsTo learn how to reuse and improve old substrate, you may be interested in our article on reuse old soil in your crops.
Can I sow directly into this substrate?
Yes. Professional substrates are ready to use in trays, containers, or cells. Before sowing, moisten slightly the mixture; fill without compacting, sow and cover just 2–3 times the diameter of the seed. Keep fine temperature and irrigation (nebulization or capillary irrigation) to avoid damaging the surface. If you'd like to learn more about how to do this, read our article on seedbeds for different plants you will be able to find useful information.
Which is better: peat, coconut fiber or mix?
It depends on the crop and the climate. Blond peat: great water retention, useful in dry environments. Coir: very good ventilation in humid climates. Peat + coconut mix: a balance between retention and oxygenation for demanding seedbeds. For a more in-depth look at the best substrates, visit our article on protected seedbeds and their care.
Key parameters of seedling substrate
- slightly acid pH (approx. 5,5–6,5) which favors the availability of nutrients without risk of toxicities.
- Low CE (low saline content) to avoid dehydration of the radicle and burns.
- Fine and homogeneous texture (sieving) for optimal seed-substrate contact and uniform emergence.
- High porosity with good retention water: air/water balance that supports germination and initial development.
- Clean mix, free of weed seeds and common pathogens; store properly after opening.
The ingredients of the seedling substrate
Compost
The first ingredient in our seedbed mix is going to be compost. Some people think of it as fertilizer, but In reality, compost has a very low concentration of necessary nutrients.What does interest us about compost is that It provides very good structure, water retention and drainage capacity, as well as many microorganisms. that will be helping our plant from the start. For seedbeds, make sure it is very ripe and well sifted to avoid lumps that prevent uniform emergence. In our article on How to make your own substrate at home you can learn how to make it correctly.
Blond peat
Is blond peat less sustainable than coconut fiber?
Peat is the product that It is extracted from peat bogs, which is a very special ecosystem which occurs only in some places in the world where there is high humidity, the water layer is very shallow and a large amount of organic matter from annual plants is generated.
With the arrival of cold weather, these plants die and begin to decompose, but the first frosts quickly arrive and this decomposition stops. Since there are fewer microorganisms due to these low temperatures, and this is repeated year after year, layers form, one on top of the other, causing the soil level to rise, forming peat. To learn more about the sustainability of substrates, you may be interested in our article on Why create seedbeds and how to do it sustainably?.
There are different types of peat, depending on the plants that make up the ecosystem and also where it is extracted from.
Commercially, we will differentiate between two types of peat: blond and black.
In any case, it's still an alteration of an ecosystem that grows very slowly. A peatland increases its ground level by about 50 centimeters every 100 years at most. So the exploitation of these areas must be controlled. Therefore, if peatland is exploited, it must be done slowly and in a very well-planned manner. In any case, 86% of the world's peatlands are still untouched and less than 1% of the product extracted from them is used for horticulture..
We fully agree that we should respect peatlands more., but perhaps this isn't the sector where the focus should be on that purpose, but rather on the many other uses currently being given to this ingredient. Coconut fiber is said to be more sustainable, especially because it's a byproduct, but requires intensive processing and washing to adjust salts and pH; the final decision may be technical and ethical balance.
Vermicompost or worm humus
The next ingredient is vermicompost, better known as worm humusVermicompost has tons of nutrients. I want to emphasize that It has a lot of fulvic acid and a lot of humic acid These are two molecules that act as hormonal regulators in plants and are extremely important in these initial stages, in addition to being a great inoculum of microorganisms for our substrate. If you want to expand your knowledge, you can also consult our article on how to reproduce plants through leaves.
Perlite
Now the next thing we'll add is perlite. Perlite is a stone that expands and becomes very porous when subjected to high temperatures. It provides aeration and lightness, avoiding waterlogging. Combined with coconut fiber or blond peat, it achieves a percentage of porosity ideal for young roots.
Sometimes It's good to have a support containerBecause mixing can sometimes be a bit tricky since the box gets so full, we take out a bit of substrate, mix it, and put it back in the box. In the end, doing it this way makes the task much easier.
Phosphate rock flour
This step is optional, but we really like doing it.
Is add a source of phosphorus to the seedling substrate mixThis macronutrient is normally present in sufficient concentrations in virtually all natural soils. It's not something you usually need to worry about unless you know for certain that your soil is deficient. This doesn't happen in many cases, but it could.
One of the best options we have for adding phosphorus is phosphate rock. Phosphate rock flour has a small amount of available phosphorus, but a significant reserve of a form of phosphorus that microorganisms will gradually release. You can learn more in our article on phosphorus. seedbeds in summer and their care.
Seaweed extract
Another ingredient we really like in our seedling substrate is seaweed extract. We use the Cultivers brand, which is Ascophyllum nodosum, which is the best of the algae we can use.
On many occasions, algae extracts are sold as if they were fertilizers, but this is not true, because the amount of nutrients they have is quite poor. They are used as biostimulants to improve vigor and stress tolerance. If you'd like to learn more about its use, we recommend our article on .
I recommend you to If you are going to use an algae extract, do so in solid form. Because at the end of the day, if we use liquid forms, all we are doing is transporting water from one place to another, and that is not very sustainable.
compost tea
We've practically finished our substrate, now we just need to moisten it a little. You can give it a light watering with water, but for us We much prefer to use a compost tea or vermicompost tea.. Moisten until, when you take a handful and squeeze it, does not drip and crumbleThis way, you avoid compacting the alveoli. This method helps keep the substrate in optimal conditions for germination, while also enhancing beneficial microbiology.
A substrate is any solid material, other than natural soil, used to grow plants, providing them with an optimal environment for development. It is the foundation on which plants will grow. In addition to supporting plants, substrates are responsible for providing crops with the nutrients they need. micronutrients and macronutrients necessary for their proper development. Therefore, choosing the most appropriate substrate for each plant is essential to ensure maximum growth. You can find more information in our article on .
El BATLLE Seedbed Substrate It is ideal for providing optimal germination conditions for seeds. It contains an exact blend of perlite and vermiculite which provide ideal water and nutrient retention. For more details on the composition, see our article on .
• Technical Features:
· Organic matter over dry matter: 58%
· pH: 7
· Apparent density compacted in laboratory: 0,33 Kg/l
· Dry Matter: 40%
· Electrical Conductivity (EC): 25 mS/m
· Nutrient content: 1,1% Nitrogen, 0,4% Phosphorus, 0,8% Potassium.
In reality, there's no set rule for determining the best substrate for seedbeds. Most substrates on the market, such as organic seedbed substrates, are composed of peat as the main ingredient, with other materials such as perlite, coconut fiber, sand, or vermiculite often added to modify the water retention, aeration, and drainage properties. Also learn how to achieve better results.
Types of substrates used in seedbeds
To create the best seedling substrate, it is necessary to address the specific germination needs of the seeds. In general, specific conditions are required. temperature, humidity and oxygenationTo achieve this, the ideal is to combine several substrates in different proportions, ensuring that each contributes its own distinct properties to the final substrate. The most commonly used substrates for this purpose are blond and black peat, coconut fiber, and universal substrate.
Black peat
When we think about using black peat to create a good substrate for seedbeds, we have to keep in mind that this substrate is composed of a highly decomposed organic matter which offers great water retention capacity, but not much aeration. On the other hand, it contains few nitrogenous nutrients, although it provides humic substances and precursors of beneficial microorganisms for the root. If you want to learn more about choosing the right substrate, we recommend reading our article on diseases in seedbeds.
Blond peat
White peat comes from the upper layers of bogs, like the different types of mosses of the Sphagnum genus. Therefore, it is a substrate very rich in organic matter. It has a coarse and grainy texture It provides high levels of aeration, which also promotes root formation, and acidifies the substrate, so it can be beneficial if our substrate is too alkaline. To learn more about its sustainability and use, check out our article on .
Coir
Coconut fiber is a 100% organic material. It provides a substrate with a high degree of porosity which promotes root development. It has a high content of lignin, which enhances the proliferation of microorganisms beneficial to plant roots and is ideal for solving substrate compaction problems. In seedbeds, it helps stabilize humidity without suffocating. You can learn more about this in our article about .
Universal substrate
Universal substrate is defined as a substrate suitable for the vast majority of crops, as each manufacturer creates its own mix of different substrates using different substrates such as peat, vermiculite, perlite, and coconut fiber, among others. Since, in general, each of them usually responds quite well to a wide spectrum of plants and purposes, it is usually quite well known and used. For seedbeds, it is advisable that your CE is not high and that texture is very fine if you're going to use it as is. You can learn more in our article about .
Which seedling substrate should I choose?
To create our special substrate for seedbeds we must imagine the final result and visualize in our minds a practically perfect substrate. inert and poorly fertilized, very well aerated and with a high water retention capacity. With this in mind, we will choose peat as the base of our substrate. Fine-fiber, slightly decomposed peat is preferable so that aeration is compatible with moisture. To achieve this, We mix blond and black peat 50%From the black we will obtain fine particles and water retention, while from the blond we will obtain less decomposed matter and improved aeration. Finally, we will add coconut fiber to increase oxygenation while stabilizing the pH of the mixture. With this simple recipe, we'll achieve spectacular results.
Before planting, pre-moisten the mixture; fill the alveoli without compacting, sow at the appropriate depth and water with fine mist or capillary action. Keep the Low CE until the first transplant; when the second true leaves appear, begin gentle feeding. You can also learn more in our article about how to customize it to your needs.
With a balanced substrate, adequate pH and adjusted watering, your seedlings will germinate successfully. homogeneous and vigorous, reducing losses and shortening the time to transplant.
