Last updated: August 7, 2021

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Welcome to our big NPK fertiliser test 2019. Here we present all NPK fertilisers that we have tested in detail. We have compiled detailed background information and also added a summary of customer reviews on the web.

We would like to make your purchase decision easier and help you find the best NPK fertiliser for you. You will also find answers to frequently asked questions in our guide. If available, we also offer interesting test videos. Furthermore, you will also find some important information on this page that you should definitely pay attention to if you want to buy NPK fertiliser.




Summary

  • NPK fertiliser takes its name from the three main nutrients it contains: nitrogen, phosphorus and potassium.
  • In general, a distinction is made between organic and mineral NPK fertiliser, as well as between NPK fertiliser in liquid form or as granules.
  • When deciding which NPK fertiliser is the right one, the composition of the three nutrients is the most important factor.

The Best NPK Fertiliser: Our Choices

Guide: Questions you should ask yourself before buying NPK fertiliser

Not all fertilisers are the same. In our guide you will find answers to basic questions about NPK fertiliser.

What is NPK fertiliser?

NPK fertiliser is also called complete fertiliser or compound fertiliser. It contains all the nutrients that plants need for balanced growth: nitrogen, phosphorus and potassium.

Eine Blumenwiese

With the right NPK fertiliser it is not difficult to make your flowers bloom so beautifully. (Image source: unsplash.com / Corina Ardeleanu)

It is available in different compositions of the three main nutrients. This means that fertiliser can be applied individually according to the needs of the different plants.

NPK fertiliser is available both as a liquid fertiliser and in the form of fertiliser pellets. Each fertiliser bead contains the same concentration of nutrients, depending on the composition of the three substances. This means that fertiliser is applied evenly with both types of fertiliser.

What does NPK fertiliser consist of?

The main components of NPK fertiliser are nitrogen, phosphorus and potassium, as these are needed by the plants in larger quantities. Other components of NPK fertiliser are calcium, magnesium, sulphur and trace elements.

Nitrogen is mainly needed for plant growth. In particular, the green pigment, which is responsible for growth, is not sufficiently formed without the right supply of nitrogen, so that the plants only grow slowly.

Verdorrte Blumen

Without enough nitrogen, the growth of plants slows down and they dry out. (Image source: unsplash.com / Annie Spratt)

As a result, the leaves are smaller, lighter or even yellowish. In acute deficiency, they dry out and fall off. Fruit formation is limited and yield and quality are reduced.

Phosphorus is essential for photosynthesis.

Phosphorus is primarily responsible for flower and fruit formation and thus also essential for photosynthesis. It promotes shoot and root formation and accelerates the development and maturation of the plant. Furthermore, it increases drought resistance and winter hardiness.

A phosphorus deficiency, on the other hand, delays the growth and maturation of the plant. It can be recognised by the fact that the leaves change colour and the plant remains small overall because the roots hardly grow.

Potassium strengthens the cell walls.

Potassium strengthens the cell walls and thus increases the plant's resistance. This also results in a lower susceptibility to diseases. Furthermore, potassium is responsible for maintaining the necessary water balance of the plants.

A potassium deficiency is indicated by brown leaf edges and tips. The formation of fruits and buds is inhibited, as only little water is absorbed and root formation is impaired.

Where can I buy NPK fertiliser?

You can buy NPK fertiliser in any conventional garden centre or florist's shop. NPK fertilisers are also available seasonally from discount stores, but only in a limited range.

Pay attention to the concentration of the fertiliser.

If you buy NPK fertiliser in a shop, you have the advantage that you can get advice on the spot. When buying, you should pay particular attention to the right concentration of NPK fertiliser for your plants.

Of course, you can also buy NPK fertiliser online. A good address for this is Amazon or Ebay or the manufacturer's online shop.

What does NPK fertiliser cost?

Since there are many different NPK fertilisers from many different manufacturers, it is difficult to compare prices. In the following table we have compiled examples of fertiliser prices for different types of plants.

Use Quantity Price
Lawn 25 kg 28€
Green plants 1 litre 8,99€
Universal 1 litre 9.99€
Bio Universal 1,5 kg 9.99€

It should be noted, however, that prices can vary greatly depending on the composition of the fertiliser. Stronger doses of fertiliser must of course be used in small quantities and will therefore last for a longer period.

What alternatives are there to NPK fertiliser?

An alternative to the complete fertiliser is the straight fertiliser. As the name suggests, this consists of only one nutrient rather than several. This is mainly used in case of acute deficiency of a nutrient.

There are also two-substance fertilisers. A distinction is made here between NP fertiliser, NK fertiliser and PK fertiliser.

Decision: What types of NPK fertiliser are there for the balcony and which is the right one for you?

There are basically three different types of NPK fertiliser:

  • organic NPK fertiliser
  • mineral NPK fertiliser
  • organic-mineral NPK fertiliser

In the following sections we present the different product types in more detail and also list their advantages and disadvantages. In this way we would like to help you find the perfect NPK fertiliser for you.

What distinguishes organic NPK fertiliser and what are its advantages and disadvantages?

Organic NPK fertilisers are "natural fertilisers". The nutrients are not present in their raw form, but have to be "extracted" from an organic structure by the plant or the soil. Before that, they cannot be absorbed by the roots.

Since many chemical reactions in the soil are involved in this process, it takes longer for organic NPK fertilisers to take effect. They therefore tend to have a long-term effect, over several weeks or months.

Advantages
  • Long-term effect
  • Natural fertilisation
  • Improving the soil
Disadvantages
  • Takes time to take effect
  • Not suitable for acute nutrient deficiencies

Organic NPK fertilisers contain many natural, organic substances from which humus can be formed. If they are applied regularly, they improve the soil.

What distinguishes mineral NPK fertilisers and what are their advantages and disadvantages?

Mineral NPK fertilisers contain the plant nutrients as "nutrient salt", i.e. in its pure, mineral form. They do not have an organic origin, as they are extracted from fossil deposits. They are therefore based on chemical substances.

As a result, mineral NPK fertilisers work much faster than organic fertilisers. They therefore release the nutrients more quickly. Therefore, they can be used particularly well as a starting fertiliser or in case of acute nutrient deficiency.

Advantages
  • Fast effect
  • Very effective in case of acute nutrient deficiency
  • Usually cheaper than organic fertiliser
Disadvantages
  • Danger of overfertilisation
  • Short-term effect
  • Partially toxic

Mineral NPK fertilisers are available either as granules, for large-scale application in agriculture, or as liquid fertilisers. The latter is administered via the irrigation water and is used especially in private households.

What distinguishes organic-mineral NPK fertiliser and what are its advantages and disadvantages?

Organic-mineral NPK fertilisers combine the advantages of organic and mineral NPK fertilisers to benefit from different rates of action and properties.

The differences between the different fertiliser types are summarised in the following video.

Buying criteria: You can use these factors to compare and evaluate NPK fertilisers

In the following we will show you which aspects you can use to decide between the many possible NPK fertilisers.

The criteria you can use to compare NPK fertilisers with each other include:

  • Composition
  • Suitability
  • Consistency

In the following paragraphs we will explain what is important in the individual criteria.

Composition

The composition of NPK fertilisers can be found in the figures on the packaging. They tell you what percentage of the nutrients nitrogen, phosphorus and potassium are contained in each case.

For the normal hobby gardener, the composition of the fertiliser for green and flowering plants is probably the most interesting.

Suitability

Depending on how the nutrients are distributed in the NPK fertiliser, it is suitable for different types of plants, flowers or crops.

In the following table we have compiled the nutrient composition for some plant species as an example. It should give you an idea of how much of the three nutrients your plants need.

Use Proportion of nitrogen Proportion of phosphorus Proportion of potassium
Green plants 14 8 20
Flowering plants 7 8 6
Turf 15 15 15
Tomato 110 25 150
Pepper 270 50 28
Onion 80 40 100
Cucumber 50 40 80
Carrot 95 40 150
Lettuce 55 25 110
Parsley 24 23 76

However, it also always depends on the yield that is to be achieved and how many nutrients are already contained in the soil anyway. In commercial cultivation, as in agriculture, much higher yields are naturally to be achieved than in private cultivation.

Consistency

Solid NPK fertiliser is mostly used for gardens and large areas. It can be spread evenly over the entire soil surface without being incorporated. This is a surface fertilisation.

Eine landwirtschaftliche Maschine auf einem Feld

NPK fertiliser in the form of granules is mostly used for large-scale fertilisation in agriculture. (Image source: pixabay.com / Barskefranck)

Moreover, solid NPK fertiliser is effective over a long period of time because it releases its nutrients only slowly. Even when it rains, it is not washed out of the soil so quickly.

Liquid fertiliser, on the other hand, is more commonly used for tub and pot plants. It is added to the soil via the irrigation water. This means that it can be quickly absorbed by the plants, but is also quickly washed out of the soil again.

Interesting facts about NPK fertiliser

You want to know more about fertiliser? In our trivia section you will not only find interesting background information, but also all kinds of useful tips and tricks about fertilising.

Is NPK fertiliser toxic?

Mineral NPK fertilisers do not contain organic substances, only chemical substances. Mineral fertilisers are therefore naturally not suitable for consumption. An example of a mineral fertiliser is blue grain.

Mineral fertilisers are "only" really dangerous if too much is consumed, but it is difficult to check what exactly too much means.

You should therefore be especially careful if animals and children could come into contact with the fertiliser.

If you want to be on the safe side, you should choose an organic fertiliser that is made exclusively from natural raw materials and does not contain any chemical substances.

Is NPK fertiliser vegan?

Vegan fertiliser is nothing other than fertiliser made from plant materials. This is the case with most organic NPK fertilisers.

In the meantime, however, there are of course manufacturers who have specialised exclusively in vegan fertilisers and advertise them separately. Here, however, the prices are usually much higher than for conventional organic fertiliser.

When should I use NPK fertiliser?

Generally, fertiliser should be applied in spring, in preparation for the vegetation phase. In midsummer, you can also fertilise again.

The last fertilisation should not take place later than July or August so that the new shoots do not freeze in winter. Balcony plants can also be fertilised in September.

The following table shows you which plants you should fertilise at which time.

Plant type Time of first fertilisation Time of second fertilisation
Lawns March/April August/September
Fruit trees and berry bushes March/April none
Roses and perennials March/April July/August
Strawberries April July/August
Balcony and pot plants May September
Tomato, pumpkin,cucumber,zuccini May July
Rhododendron,heather,azaleas March June
Conifers and firs March/April none
Climbing plants March/April none

Tips for the correct application of NPK fertiliser

If you are fertilising your plants for the first time, you should know that there are a few things to bear in mind. We have summarised the most important points for you briefly and concisely below.

  • Fertiliser should only be applied during the growing season.
  • So that the nutrients can be better absorbed, watering should be done after fertilising.
  • Fertiliser should not be applied in direct sunlight.
  • The soil should not be too dry before fertilising.
  • Fertiliser should not be applied directly to the leaves, flowers or roots.
  • Care should be taken to apply the right amount of fertiliser, as over-fertilising is bad for the plants.

Can I make NPK fertiliser myself?

There are several ways to make your own organic fertiliser. One very simple way is to simply mix coffee grounds into the potting soil. This is rich in nitrogen, phosphorus and potassium and therefore perfect to use as a natural fertiliser.

Kaffee wird aufgebrüht

Are you annoyed because you produce so much waste with your morning coffee? Why not do something good for your plants? (Image source: pixabay.com / Free-Photos)

If you prefer to use liquid fertiliser, you can simply mix the coffee grounds with water and give it to your plants in the water.

Image source: unsplash.com / Daniel Hjalmarsson
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