How to choose fertilisers for your marijuana crop

What's the role of mineral salts and trace elements?

1) The main mineral salts used in cannabis cultivation are: nitrogen, phosphor, potassium, magnesium, calcium and sulphur.

• Nitrogen (N): contributes directly to the development of plant material as it's crucial during the growth phase. It's important for the formation of a sturdy, well-developed plant structure with vigorous blade mass and thus also that of a healthy, powerful plant ready to produce great harvests.
• Phosphor (P): is an important element for the formation of roots, flowers and buds.
• Potassium (K): combined with phosphor, it boosts root formation, and together with nitrogen, it enhances the development of the plant's green tissue and of the flowers. It also considerably improves the plant's resistance to fungal diseases and frost.
• Magnesium (Mg): contributes efficiently to the production of chlorophyll, an essential element for photosynthesis and, consequently, for growth in general.
• Calcium (Ca): helps adjust the soil's pH and contributes to a good root growth.
• Sulphur (S): actively promotes the growth of different plant organs.

2) The necessary trace elements are: iron, zinc, manganese, boron and molybdenum.

• Iron (Fe): stimulates chlorophyll production and fixes the green colour on the leaves.
• Zinc (Zn): contributes to the production of the hormones responsible for the development of strong buds.
• Manganese (Mn): has an essential role in cell multiplication and facilitates nitrate assimilation.
• Boron (B): promotes water retention, which is necessary for the cells.
• Molybdenum (Mo): favours nitrate assimilation.

What's a mineral fertiliser?

Mineral fertilisers generally consist of elements of mineral origin that are mostly obtained by exploiting natural deposits. The majority of mineral fertilisers are produced chemically and contain the primary nutrients (NPK), i. e. nitrogen (N), phosphor (P) and potassium (K).

The formula varies from manufacturer to manufacturer, thus containing varying concentrations of nitrogen, phosphor and potassium. That is why each fertiliser meets the plant's nutritional needs in a different way.

So-called "mineral" manure is often concentrated, and its elements are chelated, which means they can be directly assimilated by the plant, offering immediate benefit. They work faster since they're designed to respond to an "urgent" need in marijuana cultivation. Organic fertilisers interact with the soil, so the reaction is much slower.

Mineral fertilizers could be described as a "ready-to-use" formula, and probably one of the easiest to use, but you have to use them responsibly. If you don't want to end up over-fertilising your plants, you'd better follow each manufacturer's instruction scales to the letter. As in many cases, observation is key, since it enables you to anticipate and avoid shortage or excess. It's necessary to find the adequate combination between the different nutrients to provide the right balance for your plants.

Examples of mineral fertilisers are B'Cuzz Soil Nutrition A and B'Cuzz Soil Nutrition B by Atami or Terra Vega and Terra Flores by Canna.

What's an organic fertiliser?

Organic fertilisers consist of organic waste of animal or vegetable origin, sometimes both. Those of vegetable origin often come from any type of green waste composting (grass, algae, fruit, vegetables, any kind of plants, etc.). You can also make compost teas, which are hugely effective and allow to activate or re-activate certain biological mechanisms in the soil. Vegetable solutions obtained through a maceration process, like nettle or consound tea, are excellent biological fertilisers too.

There are also fertilisers known as "green manure", i. e. plants grown and cropped on the growing area, then left to decompose or digged into the soil. Once they are decomposed, they provide minerals from deep soil layers, oxygenate and regulate nutrient surplus. There are two types of green manure; plants with a strong root system on one hand, such as rye and phacelia, and leguminous plants on the other hand, which provide nitrogen taken straight from the air, e. g. alfalfa and clover. The common effect all these "green fertilisers" share is to provide the necessary elements for a perfect development of your plants and to significantly improve soil life and structure.

Obviously, you should keep in mind that biological components don't act immediately. They first have to go through a process of decomposition and then interact with the micro-organisms in the soil. Only then will the synergy of the elements set free a wide range of mineral salts that will finally nourish your beloved plants.

Organic waste of animal origin can be made of dried bovine blood, horn meal, worm humus, seabird or bat guano, fish hydrolysate, etc. You may also use different by-products from animal breeding, such as different kinds of slurry, mostly composed of excrement and leaf litter. It is no direct organic animal material, but plants that have gone through a process of transformation in the digestive tract of different animals (dung, slurry, etc.).

Using this kind of organic manure in biological crops will take more time, since you'll need to acquire some previous knowledge first, but once you've overcome this obstacle, it's certainly a practicable, sustainable solution.

What's an organic-mineral fertiliser?

Organic-mineral fertilisers are simply a mixture between mineral and organic fertilisers. Nitrogenous organic matter usually represents about 25 or 50% of the whole product. The other components of the fertiliser, simple or mineral salts, i. e. N-P-K sources, are diluted in the organic matter.

Growers often notice that some liquid manure containing organic matter isn't stable anymore once it's mixed with mineral manure. This is due to the decompositions of organic matter, which causes a clogging of sewers and pipes of many automatic irrigation systems.

We therefore recommend using chelated mineral fertilisers to all growers working with these systems that don't want to get confronted with such problems.

Happy growing everybody!