What does N-P-K mean on fertilizers?

What does N-P-K mean on fertilizers?

What does N-P-K mean on fertilizers?
Fertilization (N-P-K-Mg-etc.)

What does it mean, what is it, what does it do, what happens if you have too much or too little of NPK?

Take a look at any bag/package of fertilizer or compost. They are all nutrients that your plants, whether they are flowers, vegetables, trees or weeds, need to grow or flourish. A bit like needing food. We have the five-disc. And plants, of any kind, also have sort of their own disc of nutrients that they need in certain amounts. And just like with people, there are substances that make you happy or sick when you get too much or too little.

So, to start with the letters:

    Carbon = C
    Hydrogen = H
    Oxygen = O
    Nitrogen = N
    Phosphorus = P
    Potassium = K
    Magnesium = Mg
    Calcium = Ca
    Sulfur = S

Well, that's quite a few letters. And then there are the essential trace elements:

    Iron = Fe
    Manganese = Mn
    Zinc = Zn
    Drill = B
    Molybdenum = Mo
    Copper = Cu

And then some trace elements of which it is not yet completely clear (or at least not scientifically proven) that they are useful for plants:

    Silicon = Si
    Cobalt = Co
    Sodium = Na
    Chlorine = Cl
    Iodium = I
    Aluminum = Al

All of these nutrients are absorbed by the plant and have a certain function. The following describes what these substances are and what they do or do not do to a plant. It may be useful later to find a good fertilizer, in general, or for example if you notice a disease or lack in a plant (e.g. yellow leaves, poor growth, etc.) Some specific. Because maybe that plant is missing an essential substance, or maybe the plant has received too much of a certain substance (let's call it overfeeding), also unhealthy.

Carbon, hydrogen and oxygen (C, H and O).

These are the 3 easiest elements. They are the 3 essential building blocks of the plant that you don't have to do anything about. A plant is primarily made up of these 3 elements. So it's carbon and oxygen, which is present in the air. And water, which comes down by itself.

The only thing you have to do to make sure that the plants can absorb these substances through the roots, is to make sure that the plant is planted in soil, that it is not smothered by plastic or other non-permeable material, and give them water when it does not fall from the air by itself to a sufficient extent (and make sure there is good drainage so that in case of too much rain the water can drain sufficiently)

Nitrogen (N)

What does it do?
- Nitrogen is a component of chlorophyll, the substance that gives leaves and stems their green color. Nitrogen promotes plant growth: stems and leaves, so-called vegetative growth. It also produces plant proteins in the plant.

What happens when there is too little nitrogen
- Leaves turn yellow, the plant does not grow well.

What happens if there is too much nitrogen
- Large but weak plants with many watery stems and leaves.
- Plants become susceptible to fungi, pests and diseases.
- More susceptible to frost
- Slower flower and/or fruit formation - Less easy to store after harvest - Increased uptake of the poisonous substance nitrate (converts to nitrite = harmful to humans!).

Sources with relatively high nitrogen content
- animal manure
- blood meal

Phosphorus (P)

What does it do?
- Plays an important role in plant respiration and energy supply
- Promotes root development of young plant roots
- Promotes flowering, seed formation, and maturation
- Promotes crop life
- Promotes tuber formation in vegetable tubers

What happens when there is too little phosphorus
- Abnormal bluish leaf color and/or purple discoloration of leaves.
- Poor lateral root growth and development
- Phosphorus deficiency is common in a wet spring, when soil life cannot make phosphorus available to the plant.

What happens when too much phosphorus
- There is no direct adverse effect of too high a phosphorus content, but it can indirectly cause a shortage of Zinc and Iron.
- If large amounts of phosphorus are administered each year, the phosphorus will no longer be absorbed by plants and soil and will be washed away (with consequences for nature).

Sources with a relatively high phosphorus content
First of all: give enough phosphorus to young plants, which absorb 75% of the total phosphorus in the first part of their lives.
- Farmyard manure
- bone meal
- Natural phosphate

Potassium (K) (they are called Kalium too)

What does it do?
- Necessary for water and carbohydrate transport
- Promotes plant firmness
- Promotes root and tuber formation
- Promotes fruit and flower formation
- Reduces drought and frost sensitivity
- Increases resistance to fungal diseases
- Promotes flavor and crop shelf life

What happens when there is not enough potassium
- Gives color spots and leaf wilting, starting at the leaf edge
- Fewer large and poor quality flowers, buds or fruits
- Reduced tuber and root formation
- More sensitive to changing climatic conditions

What happens if there is too much potassium
- Plants (and therefore also the vegetable crop) hold more water
- Impedes the uptake of Magnesium and Boron by the plant.

Sources with a relatively high potassium content
- Farmyard manure
- Stone meal
- Vinassekali
- Bonemeal

Magnesium (Mg)

What does it do?
- Plays a role in photosynthesis (absorption of sunlight and conversion of light into energy).
- Plays a role in different chemical reactions in the plant.

What happens when there is too little magnesium
- Leaf discoloration where the leaf mass turns yellow and the leaf veins remain noticeably green.
- Magnesium uptake in spring is limited by low temperatures.
- The risk of magnesium deficiency is higher in sandy soils than in loamy and small soils.
- At low Ph, magnesium is less easily absorbed and its leaching is higher.

What happens when there is too much magnesium
- This is rare and, as far as we know, can do no harm.

Sources with a relatively high magnesium content
- Dolomite lime / seaweed lime
- Farmyard manure
- Kieserite

Calcium (Ca)

What does it do?
- Plays a role in nutrient uptake and various chemical reactions in the plant (e.g. acidic compound)
- Improves soil structure
- Promotes nutrient uptake, especially in acidic soils

What happens when there is too little calcium
- Long-term impoverishment of soils and reduction of humus content, especially in acidic soils

What happens when there is too much calcium
- Too high Ph in the long term with important consequences for plant food supply.

Sources with relatively high calcium content
- Rocks; e.g., limestone marl, dolomite lime
- Seaweed lime
- Agricultural lime
- Chicken manure

Trace elements

Trace elements, are only needed in very small quantities but those small amounts are indispensable for the plant. In a well-maintained organic garden you will rarely see a shortage of trace elements because all trace elements are found in compost, farmyard manure and other organic materials used in organic gardening.

Trace elements that have been shown to serve a useful function for a plant:

Iron (Fe): important in chlorophyll production and for plant respiration. When missing, fine colored spots of young shoots and leaves are seen, veins remain green. It is sometimes confused with magnesium deficiency, which causes the same deficiency symptoms. A surplus of iron fixes phosphate in a form not absorbable by the plant. Manganese (Mn): plays a role in cell division, photosynthesis and metabolism. Lack of manganese causes discolored yellow spots on shoots and between the veins of older leaves, which therefore do not develop well. The taste of vegetables can be deviated due to manganese breakdown. In case of manganese breakage, add seaweed lime, farmyard manure or compost. An excess of manganese is poisonous to the plant. Boron (B): also called Boron, plays a role in the transport of nutrients in the plant. Boron deficiency is recognized by black spots on young leaves and the disappearance of the growing point. Boron deficiency occurs mainly in sandy soils, after liming, when there is too much nitrogen and/or potassium and when there is drought. In case of Boron deficiency it is usually too late for the plant, provide a preventive treatment by adding seaweed lime, farmyard manure or compost to the soil every year. Molybdenum (Mo): plays a role in nitrogen supply. Molybdenum deficiency is recognized by discoloration of leaf margins. Molybdenum deficiency actually only occurs in acid soils and the best remedy is to increase the Ph (with lime). Silicon (Si): makes plants firmer and increases their resistance to fungi. Silicon deficiency is recognized by growth inhibition and weak and pathetic plants. An infusion of horsetail contains silicon.

In addition, there are a number of trace elements that have not yet been scientifically proven to have a function for a plant, but have been found as a substance in plants. Examples are cobalt, sodium, chlorine, nickel, chromium, selenium and iodine. An excess of these substances usually has a harmful and/or toxic effect on the plant.


If you have read the above and added it all up, you will undoubtedly see that there is usually no single defect, no single solution. Sometimes you may think that a plant is getting too little nitrogen, but then there is too little nitrogen in the soil, or it is there but the plant cannot absorb it, due to a lack of another element, for example? It takes a while, but you have to know your own soil, learn what a certain Cannabis or vegetable needs (e.g. leeks don't grow without enough nitrogen), learn what a plant doesn't want (e.g. beans get big and mushy and get sick with too much nitrogen).

So you need to make sure that your soil is in order, adding a good content of humus. Because of all the compost and old farmyard manure there is a lot of humus, a lot of life in the soil, more aeration, a lot of necessary trace elements. And that's the best base for the indoor and outdoor garden. It ensures that when we use fertilizers, they can be absorbed by the plants. And remember: too little nutrition is not good, but too much nutrition is not good either, you will have to find the right balance in your garden yourself.

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