How to Fertilise: A Complete Guide to Buying Plant Nutrition
How to Choose Fertilisers: A Complete Guide to Buying Nutrition for Your Plants
On the market, you will find dozens of brands and hundreds of different types of fertilisers – in liquid, powder and solid form, organic and mineral, for different growth stages and cultivation methods. How do you make sense of it all and avoid mistakes? We have prepared an overview of the basic types of fertilisers and practical advice to help you choose the right nutrition for your plants.
Basic Types of Fertilisers by Growing Medium
There is a difference between fertilisers for growing in soil, coco, inert substrates or hydroponics. Before you start buying fertiliser, make sure which substrate and which growing method you want to use. Only then can you choose the right type of nutrition.
- Fertilisers for soil: These are suitable for growing in open ground (in beds) or in pots.
- Fertilisers for coco substrates: Growing substrates made from coconut fibres do not contain nutrients on their own and require special fertilisation. Coco substrates are usually used for indoor growing or in greenhouses.
- Fertilisers for hydroponics: These are intended for preparing a nutrient solution for substrate-free systems or when growing in inert media such as rockwool.
You may also be interested in: Guide to Growing Substrates
Choosing Fertiliser According to the Growth Stage
From germination to harvest, plants go through several growth stages, and their nutrient requirements change accordingly. During the first weeks of life, they need little or no fertiliser; during the vegetative growth stage, it is important to provide enough nitrogen, and during flowering it is suitable to use fertilisers with a higher content of potassium and phosphorus.
- Starter fertilisers-Start: These contain a small amount of nutrients and often also substances that support root growth and beneficial microorganisms, such as mycorrhizal fungi or soil bacteria.
- Fertilisers for the growth stage-Grow: These contain an increased amount of nitrogen, which plants need for the formation of leaves and stems. Nitrogen fertilisers can be purely organic, mineral or combined, and the nitrogen in them may be present in the form of nitrates (NO₃-) or ammonium (NH₄+), which affects the absorption rate and influences pH fluctuations in the substrate.
- Fertilisers for flowering-Bloom: These contain larger amounts of phosphorus and potassium to support the formation of flowers and fruits, and like other types of fertilisers they can be organic, mineral or combined.
- Fertilisers for the pre-harvest period-Flush: Especially when growing medicinal plants, some growers stop fertilising several weeks before harvest and replace it with clean water or special flushing fertilisers or finishers. The aim is better aroma and taste of the resulting product.
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Organic vs. Mineral Fertilisers
Although it makes no difference to plants which source the nutrients absorbed by the roots come from, the difference between organic and mineral fertilisers is significant in cultivation. Organic fertilisers are effective only in the presence of soil microorganisms and are therefore suitable only for growing in soil-based (organic) substrates or in beds. Synthetic fertilisers contain mineral salts that plants can absorb directly from water and can be used for growing in coco, inert substrates and in hydroponics.
- Organic fertilisers: These are made from natural raw materials such as compost, manure, bone meal, guano, fish, seaweed or plant extracts. When using organic fertilisers, keep in mind that it takes some time before they start to work.
- Mineral fertilisers: These contain nutrients in the form of mineral salts, which are obtained from phosphates, ammonia and the synthesis of nitrogen from the air. They work immediately and carry a risk of over-fertilisation. Therefore, always follow the dosage tables and measure the pH and EC of the nutrient solution.
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Fertiliser Form: Liquid, Solid or Powder?
Fertilisers can come in several forms – from fully liquid to loose to solid with slow release. Each form has its advantages; it depends on where and how you grow. Different forms can include organic, mineral or combined types of fertilisers.
- Liquid fertilisers: Concentrated fertiliser solutions for preparing nutrient solution are the most user-friendly. They work quickly, are easy to handle and have a long shelf life.
- Dry fertilisers: Water-soluble fertilisers in powder or granule form can be used to prepare a nutrient solution or applied directly to the substrate (if they are designed for that purpose).
- Solid slow-release fertilisers: Fertilisers in the form of pellets or granules with slow release are suitable for outdoor growing because they leach from the soil more slowly and supply nutrients to plants gradually. The disadvantage is that they are more difficult to dose.
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Complete Nutrition: Multi-Component vs. Single-Component Fertilisers
Especially with fertilisers for hydroponic growing, it is common to use multi-component fertilisers that are mixed in a ratio to create the ideal nutrient solution for a given occasion (for example, more nitrogen during the growth stage or more phosphorus and potassium during the flowering period). On the other hand, there are single-component fertilisers, which contain a given ratio of nutrients, usually for a specific growth stage (veg/flower).
Nutrition Additives and Stimulators
In addition to basic fertilisers, which contain the macro- and micronutrients essential for plant growth, you will also find a range of supplementary nutrition and growth stimulators on growers’ shop shelves. These additives are not usually essential for cultivation, but many growers use them to bring their plants to perfection.
- Root stimulators: These speed up root formation and are used during germination, taking cuttings or transplanting plants.
- Growth and flowering boosters: These stimulate plants to form leaves or flowers.
- Vitalisers and enzymes: Various types of additives for protecting plants from stress and supporting microbial life.
You may also be interested in: When and How to Use Root Stimulators
You should now be ready to buy the appropriate fertilisers for your plants. Before we leave you, however, we would like to add a few final tips.