Cropping with mapito, the suitable substrate for hydroponic plantations

Cropping with mapito, the suitable substrate for hydroponic plantations

Mapito is an increasingly popular substrate in hydroponic growing systems and stealth grow box ideas. It is a compact mixture of rock wool and polyethylene flakes, a more solid base than others used in hydroponics, but with the same moisture retention and higher oxygenation. A cannabis crop with mapito will not only grow faster, in about nine weeks of flowering, but will give high quality results if you adjust the electroconductivity (EC) and pH every week according to your needs. We tell you about it in this guide.

This curious growing substrate called mapito is a first cousin of rockwool, a fiber developed in the 20th century from an artificial process that mimics volcanic lava. Rock wool is highly valued in agriculture, especially in indoor cannabis cultivation. It is capable of retaining moisture well, which is essential in hydroponic cultivation, since here watery solutions take precedence over soil, and it is desirable to have a stable substrate that absorbs well.

However, rockwool is a fragile material that often tends to clump together, so a group of Dutch growers decided to mix it with polyethylene and give it a separate lump or flake shape. Therefore, the mapito presents the qualities of rock wool but in a more compact form, which not only helps to move it more freely but also facilitates the oxygenation of the roots through the small spaces left between its shavings.

The problem with rockwool slabs is that the plants must not move, as this could cause damage to both the plant and the roots. With the mapito this does not happen, we can transport it from one place to another without excessive concern thanks to its granular consistency, which on the other hand also helps to improve oxygenation and porosity, two very important characteristics for hydroponic pot cultivation.

But the products of this type of cultivation must also be careful that the mapito does not become caked and remains detached. If the substrate ends up very compressed, not only would it lose all the qualities mentioned above, but we would also be making it difficult for the roots to grow and risk the plant not growing well or even withering if they rot.

Start cultivation with mapito

Once we are clear about the qualities of the mapito, it is important to take into account that, just like rock wool, it must be stabilized and properly moistened before starting cultivation. The substrate must be cleaned to leave it free of salts or residues that it may bring as standard, as this would affect the EC levels later on. To do this, the whole mapito must be soaked in a container with water and check that the EC is as low as possible (around 0.3).

After cleaning the entire layer, check the pH levels and stabilize them to a range of 5.5. In short, it is necessary to start the crop with an EC as low as possible and with a stable pH so that the plants absorb nutrients properly from the beginning. It is also essential to keep the mapito moist once we add the seedling or cutting, so the ideal time to start planting would be when we remove the water from the wash.

When the mop absorbs water it is crushed a little, leaving a hole around it, so we will have to fill in the spaces left with more mop, as many times as necessary. The substrate will contract many times after watering it, so it is important to check it frequently and cover the holes in the pot.

When we put the previously germinated seed in the pot it will also be necessary to put a lid, with two small holes: one through which the stem of the plant will come out and another through which we will supply the drip from the hydroponic system. It is necessary to avoid at all costs that the roots come into contact with light, because this would ruin our culture, besides which it is a fairly effective method against algae that sometimes grow in the substrate.

During the first two weeks, when the roots grow more, it is convenient to rotate this lid so that the drip reaches all parts of the pot equally. To feed the plants during this phase it will be enough with two daily irrigations of about 60 ml, keeping the low levels of EC and the stable pH as we had indicated before. In the beginning we must provide the irrigation with nutrients such as those from the root stimulators; in this first phase we will not observe so much growth of the stem, since it is the root system that is developing inside the mapito.

Cannabis development in mapito

From here on, over the next two weeks we will gradually increase everything: EC levels will rise to 0.7-0.8, pH to 5.9 and watering to three a day. In this new phase it is important to control the temperature and that there are no sudden changes (of more than 4 ºC) between night and day; this will help the plants not to grow too much upwards and thus their flowering will be more abundant.

In the third and fourth week of growth the EC levels will reach 1.0 and the pH will remain at 6.0. We will start to notice how the buds grow in quantity and volume. It will be better to do a small root wash to remove any residues that may have been left in what we have been processing.

During the fifth and sixth week we will need to increase the EC to 1.2 points and keep the pH around 6.0. This time we will add one more irrigation per day and we will be very attentive to the temperature, which should be around 25 ºC, and the humidity, between 50% during the day and 60% at night. At the end of this stage it is advisable to wash the roots thoroughly, with 3 litres of water per pot to eliminate any salts left on the mapito. The seventh week of flowering will be the final one, and only the buds will be left to mature; here we will reach a maximum of 1.4 EC and 6.2 pH.

In the last two weeks you have to let the plant finish maturing the buds and give them more consistency than they have. In the eighth week you will reach the ceiling of the EC level by 1.6, but you will reduce the base food, so that you can already dedicate the ninth week to clean the plant of salts. While the trichomes are darkening and the leaves are losing color, it is necessary to make a wash like the one of the principle (with a minimum of EC and the stable pH in 6.0). Afterwards, all that remains is to harvest the results and prepare them for healing.

This is a quick and simple process, but it requires pH and EC meters to keep the mapito under control throughout the process. The root system developed in this substrate absorbs nutrients better than any other, so we will also need less fertilizer than if we use soil or other substrate. Undoubtedly, the mopito is the ideal substrate for hydroponic cultivation and every day more and more cannabis farmers are applying it in their indoor plantations.

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