What fertilizers to use? Part 2


In the previous issue of ROOTS magazine, we talked about the broader division of fertilizers that are available in grow shops, and we discussed in detail the basic organic fertilizers and additives. In this part we will focus on the second option from the basic group of fertilizers, which are mineral fertilizers.

Mineral (synthetic) fertilizers are often neglected by growers because they are produced artificially using chemical elements and their compounds produced in laboratories. However, the fear of using these fertilizers is not entirely justified in terms of their use for cannabis cultivation.

Cannabis plants are currently used due to their strong ability to pull heavy metals out of the soil, which suggests that these plants are able to hold a large number of elements that are not needed for cannabis for the growth or flowering phase.

The use of cannabis plants for soil cleaning is currently being considered, for example, in Chernobyl, for which the Czech association TRAWA is most committed, but that is a different story…

These elements are then either used by the plant and consumed for their benefit, or stored in it. Only certified fertilizers that do not contain heavy metals and contain only elements that can be fully utilized and consumed by the plant are on the shelves of grow shops.

In any case, when using mineral fertilizers, it is recommended to stop fertilizing the plants before organic fertilizers, so that the plant can fully consume all the nutrients and thus achieve the best taste of the product grown. However, this also depends, among other things, on the medium in which the plants are planted.

When using mineral fertilizers in earthy substrates that have the property of storing nutrients (non-inert media), it is recommended to stop fertilizing 2-3 weeks before harvest to get the best taste of the crop.

Some growers stop fertilizing even earlier, but it always depends on the type of fertilizer, the amount of additives, the length of the plant's flowering cycle and, of course, whether the plants are planted in a pot or loose in the soil.

Occasionally, there may be a problem where the grower stops fertilizing the plants too soon, and the plant does not have the necessary elements for the proper development of inflorescences. This can cause small harvests, non-compact inflorescences and, in extreme cases, plant death.

If a number of fertilizers also have higher amounts of additive-based products, there may also be a problem with the deficits that begin to manifest on the plant. At a time when plants have a large number of elements available to them, which are supplied to them at regular intervals, it can be said that they will get used to the supply of these elements and will miss them after planting basic fertilizers and additives.

Another factor for the timely interruption of fertilization is whether the plants are planted in a pot or loose in the soil. In the pot, it is possible to shed the plants and thus get rid of the accumulated mineral salts from the pot. Plants planted loose in the soil have a higher amount of nutrients accumulated around them, which cannot be washed away, so it is good to stop fertilizing the plants a little earlier so that all the elements are consumed.

Last but not least, it is also important to find out in advance about the length of flowering of a certain species of plant, either on the Internet or from the mother from whom you have clones. Most likely, they will not share this information with you in any seedshop, as cannabis seeds are sold here only for collecting purposes.

When grown in inert media such as coconut, rockwool, mapito, phytocell, expanded clay / hydroton and perlite, it is possible to fertilize a little longer because these media have a certain absorbency, although small, so they can minimize nutrients in themselves or indoors. keep flower pots. Therefore, it is recommended to stop fertilizing 2 weeks before harvest.

It is a little different when growing in DWC, NFT or aeroponic systems. In these systems, the plants are not planted in any medium that should retain the required amount of nutrients. Therefore, when replacing the nutrient tank with clean water too soon, the plants will very quickly start to lack the necessary elements. Plants are also able to consume all the nutrients stored in them faster, so we should not stop dosing fertilizers into these systems earlier than 10 days to one week before harvest.

If the grower is not sure whether the plants are properly cleaned, do not naturally turn yellow and are deep green, or fertilized for a long time and the resin glands of the plant are already ripe, it is possible to use products that are generally referred to as "flush". These preparations dissolve the accumulated salts in the medium and the plant is able to absorb and utilize existing nutrients faster. These products can also be used in the event of plant fertilization.


Another way to prevent the accumulation of salts or over-fertilization is to continuously supply the plants with enzymatic components at regular intervals. Enzymes dissolve salts, destroy dead roots and cleanse healthy roots, thus boosting nutrient intake.

When using mineral fertilizers, it is also good to occasionally plant fertilization and water the plants only with water, enzymes, or fertilizers that are not based on NPK. Most schemes that determine the dosage of fertilizers from different manufacturers do not indicate whether the fertilizers should be supplied with each dressing or, for example, only once a week. In any case, you will never make a mistake if you omit the fertilizer once in a while during manual watering - you avoid over-fertilization or oversalting of the soil, which is manifested by white crystals on the surface of the substrate.

In systems where plants spice up water, but keep in mind that there are always fertilizers needed.

When choosing mineral fertilizers, find out their composition. Some fertilizers are composed only of raw elements and some of the elements that are bound by a certain chelate.

Simply put, a chelated element (most often EDTA) is more readily available to the plant and can be more easily absorbed by the plant even if no pH correction has been made. Thus, the more a basic fertilizer or additive has chelated elements, the better.

As for the pH correction itself, it is really better to adjust the pH in the case of mineral fertilizers. Some elements are available to the plant only at a certain pH value. In the case of organic fertilizers, we have said that these fertilizers are taken in directly by the plant, so it is not so necessary to adjust the pH here. However, for mineral fertilizers that are composed of salts, this is recommended because plants simply do not reach certain elements when the pH is wrong.

Exceptions are fertilizers, which have an automatic pH correction, which, when properly dosed and adding all the necessary components and additives, will create the conditions for the plant to receive all the necessary nutrients.

As for the structure of mineral fertilizers, they are mainly liquid fertilizers and powder fertilizers.

Liquid fertilizers are most often represented because there is more emphasis on the distribution of elements that are separated into multiple bottles, so the grower can intervene more quickly in case of deficits. However, dosing is a bit more complicated when used in recirculation systems. This is because the grower supplies all the individual components of the product line in the quantity specified by the manufacturer in order to reach a certain EC value, but if he constantly replenishes his nutrition tank and does not change the tank, he never
it cannot know exactly which element, or component, is added to the tank, so in most cases the pH values fluctuate.

Another problem that can occur with insufficient tank replacement is that some of the components begin to settle at the bottom of the tank, form mucus or precipitate, and may become clogged with capillaries, needles, or spray valves when mixed.

As for powder fertilizers, they have smaller product lines and most often consist of a basic fertilizer for growth, for flowers and possibly 2-3 additives, so dosing is much easier. Powdered fertilizers that are currently available have higher NPK values than liquid ones. Their advantage is that they can be dissolved in water longer than liquid fertilizers and the tank does not have to be changed as often.

However, the disadvantage is the solution of deficits, because powder fertilizers contain a number of elements, so if the grower wants to solve the deficit and can use only a few products, it may happen that although the deficit is solved, there may be an excess or blockage of another element and fertilize the plant.

In the next part of this series on fertilizers, we will analyze organo-mineral fertilizers and talk about the division and use of different types of additives. So fist well and again next time!

"When grown in inert media, it is possible to fertilize a little longer"

"As regards the structure of mineral fertilizers, they are mainly liquid fertilizers and powder fertilizers"