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What does N-P-K mean?

Posted on May 13 2019

What does N-P-K mean?


No doubt you may have noticed the letters N-P-K, combined with some figures, on the packaging of fertilizer bags. What do these letters and figures stand for?

The meaning of N-P-K

The letters N-P-K are short for the scientific names of nutrients in fertilizers:

  • N stands for nitrogen
  • P stands for phosphor
  • K stands for potash (or potassium)


Important nutrients for plants

Nitrogen, phosphor and potash are the main nutrients for plants. Nitrogen is necessary for its growth and phosphor for the development of roots, buds and flowers. Potash is vital for sturdiness, flowering and fruiting, and a better resistance (as in protection from mould and diseases).


What exactly is ''N-P-K-value''?

The figures following the letters show the nutrients' proportions in that particular fertilizer. For instance, a fertilizer with the code N-P-K 12-10-18 contains 12 percent nitrogen, 10 percent phosphor and 18 percent potash.


How do I know what my plants need?

The amount of N-P-K and its proportions your plants need depend on the plant and also on the substrate it is growing in. Some substrates by nature contain more nutrients than others, whereas many substrates do not contain any N-P-K at all. So best of all choose a fertilizer that is tailored to meet the specific requirements of the substrate, for instance AWA Leaves A of B for hydrosubstrate, ATA Coco Max A of B for coir substrate or B'cuzz Soil Nutrition A of B for soil substrate..


Plants that need nitrogen (N)

Nitrogen promotes plant growth. So, primarily plants in their growing phase need this nutrient. Whilst in their growing phase plants develop all of their green parts growing above soil level, in other words: stems and leaves. As nitrogen partly ensures the development of chlorophyll it supports the process of photosynthesis. Of course, nitrogen is not only helpful in a plant's growing phase but also in other phases. Leafy vegetables such as lettuce, kale, cabbage and spinach, being genuine nitrogen lovers, particularly profit from it.

Symptoms of nitrogen deficiency
  • Leaves turning yellow
  • Lack of growth


Symptoms of excess of nitrogen

  • Sensitivity to moulds and plagues
  • Large but floppy plants; a profusion of stems and leaves but hardly any fruit


What does N-P-K mean?

Plants that need phosphor (P)

Phosphor stimulates good root development, so it is vital for any plant: the bigger and sturdier the root-ball is, the stronger and healthier the plant will be. But not all plants establish deep roots. In the kitchen garden, for instance, leafy plants need less phosphor than root vegetables do. Incidentally, phosphor also helps the photosynthesis process along by converting the sun's energy to usable energy for plants.

Symptoms of phosphor deficiency
  • Leaves turning blue or purple
  • Hampered growth


Symptoms of excessive phosphor

  • Should you offer too much phosphor to your plants, they will be unable to absorb it, causing phosphor to leach into the soil and thereby into nature. So while the plant does not really suffer, nature does. In other words, excesses of phosphor (particularly on a large scale) are bad for the environment and even affect our drinking water.


Plants that need potash (K)

Potash provides sturdiness, flowering and fruiting, and a better resistance to infections. So clearly this nutrient is as important to any plant as nitrogen and phosphor are, for don't we all wish for healthy, disease-resistant plants? Having said that, the proportions of N-P-K might vary as regards plants producing abundant flowers, for they will flourish on some extra potash, which helps them to develop their flowers. Potash also stimulates seed development, thereby promoting cultivating of all sorts of plants.

Symptoms of potash deficiency

  • Less large and well-formed flowers and less strong tubers and/or roots
  • Coloured spots and withered leaves, often starting from the leaf's edges


Symptoms of excessive potash

  • Plants and fruits contain a lot of water
  • Less absorption of magnesium (Mg)



Sometimes you'll find the letters ''Mg'' added to N-P-K, meaning that particular fertilizer contains some magnesium too. Magnesium produces chlorophyll, a key element in keeping plants healthy.