How to Choose the Best Fertilisers?

Are you going to start growing and don’t know how to choose the right fertilizers? There is no need for despair! Whether you want to grow indoors or outdoors, the following article will provide all necessary information on how and when to use fertilizers in your grow room or garden.

Plants are like people – they need nutrients to live and thrive. However, unlike humans, plants receive the nutrients through their roots from the soil or any other growing medium. In nature, nutrients travel from soil to the roots thanks to processes that require abundant microbial life. Fertilisers come into play when natural sources are insufficient or non-existent, for example in hydroponics (growing in nutrient solution). What is more, even when growing in nature we can help plants by carefully using the right types of fertilisers. The reward for us comes in the form of tastier harvests and higher yields. So the one million dollar question is: According to what parameters shall I choose the most convenient fertilisers?

Outdoor or indoor?

Do you grow plants in soil in your garden or under artificial lighting indoor? For outdoor cultivation, fertilisers in powdery or solid form are suitable, as they can be incorporated into the soil right before the seedlings are planted. If the situation requires, they can also be added later during the growing cycle. High-quality organic fertilisers from the brands such as Guanokalong and BioTabs are often the preferred choice of professionals. Not only will your plants grow wildly thanks to these products, but they are also ecological and sustainable.

Liquid fertilizers are not always suitable for outdoor growing because they spill easily into the surrounding environment. When you use them, at least choose from organic ranges. The advantage of organic fertilisers is that they are environmentally friendly and the soil in the growing area remains healthy and has a good quality.

Piece of advice: If the soil in your garden or greenhouse is depleted, you can enrich it with a good quality soil mix or vermicompost before the spring season commences.

Indoor growers usually work with water-soluble fertilisers. They are being added to water every time the grower irrigates their plants. The reason behind this is that there are barely enough nutrients in the small amount of potting soil to keep the plants thriving until the harvest. When growing indoors in soil, one can pick organic or mineral fertilizers, but it is important to note that mixing the two is a very bad idea. Mineral salts damage the microbial life in soil needed for organic fertilizers to work properly.

There is a very specific feature of hydroponic growing: the roots of the plants absorb nutrients directly from the water. Plants can be placed in one of the inert substrates created for hydroponic growing or they can have the roots submerged directly in water. In either case, the nutrient solution needs to be balanced and filled with the right amount of nutrients from fertilizers made for hydroponic growing (link) and you always need to maintain the correct EC and pH.

Related: EC and pH 

What fertilizers to choose for growth and flowering?

Plants can absorb 13 different elements from the soil or nutrient solution. However, three of them are absolutely crucial: nitrogen (N), phosphorus (P) and potassium (K). Plants need them in the greatest amount and thus they are called macronutrients. Labels on bottles or powder mixes indicate the content of these three elements by numbers in N-P-K order. For example, the numbers 4-3-6 for BioBizz Grow fertiliser indicate a proportion of 4% nitrogen, 3% phosphorus and 6% potassium.

The intake of NPK varies greatly during the life cycle of our plants. In the first part of their life, which we call the growth stage when plants are creating new branches and leaves, they need the most nitrogen. Thus, the appropriate NPK ratio for the growth period is 3:1:1.

Piece of advice: If you are growing in pre-fertilized substrate (link), it most likely already contains a substantial amount of nitrogen for just about the first four weeks of the growth phase. In such cases, apply carefully one of the lower nitrogen fertilizers (link) or do not use fertilizes during this period at all.

As plants enter the flowering stage, their nitrogen intake decreases and they start consuming more phosphorus and potassium. In the first part of the flowering phase, the appropriate NPK ratio of 1:3:2. As plants mature, we can skip nitrogen completely and choose one of the effective PK mixtures to stimulate rich flowering, such as PK 13/14. In the last two weeks before harvest, a number of experts recommend irrigating plants with clean water only. In recent years, however, there have been scientific studies suggesting that this practice is not necessary. Still, we may have to wait a few more years until there is scientifically confirmed conclusion regarding this method.

Piece of advice: When growing with fertilisers high in mineral salts, use a flushing solution in the last two weeks.