Best Characteristics of Fertilizers for Plants


Best Characteristics of Fertilizers for Plants

Characteristics of Fertilizers for Plants

NPK – what’s it all about?

You have surely seen the letters NPK written on the packaging or in specialist magazines,  but do you know what they mean?

NPK, the Basic Nutritive Elements

NPK fertilizers contain the three main nutritive elements needed by plants during their development stage. These elements are drawn from the substratum. They will be used up quicker in a pot or in a window box than in a garden, so they will need to be replaced regularly.

  • N stands for nitrogen, an element that helps the vegetative development of all parts of the plant above the ground. It is beneficial when planting, in Spring when vegetation begins, and for leafed vegetables. However it should be carefully dosed as too much of it may hinder the development of flowers, fruit, and bulbs. It can be found in dried blood, cut grass, and in nettle slurry.
  • P stands for phosphorus, a nutritive element that strengthens resistance in plants and helps root development. It can be found in bone powder and in bird droppings.
  • K stands for potassium, an element that contributes to blossoming and fruit development. It can be found in wood ash.

The letters NPK are followed by three figures on fertilizer for plants packages which correspond to the proportion of each of these elements in the product.  For example, a tomato fertilizer NPK 12.10.20 contains 120 grams of nitrogen per kilo.

Examples of NPK proportions for specific fertilizers for plants:

  • Fertilizer for citrus fruit: NPK 14.4.28
  • Fertilizer for lawns: NPK 20.10.10
  • Fertilizer for geraniums: NPK 4.6.8
  • Fertilizer for fruit trees: NPK 5.4.8

Other elements fertilizers

Other so-called ”secondary” elements are also essential for proper plant development such as calcium (Ca), sulfur (S), or magnesium (Mg).  Less of these are needed and often there is enough of these in the soil.

Trace elements also play a determining part in plant development, contributing to the formation of chlorophyll and healthy growth.

Nutrients or Fertilizing Agents

It is necessary to regularly fertilize your soil, especially if the plants are close together and in reduced spaces like window boxes or flower pots.

Different Fertilizers For Plants

General fertilizers (8% N, 8% P, 8% K), whose composition is balanced for all plants.

Compost from the decomposition of vegetable matter rich in nitrogen.

Manure is an organic fertilizer for plants rich in nitrogen and in trace elements.
There are different types of manure:

 fresh cow dung improves light soils Fresh

  • horse dung and donkey dung, with their drying powers, improve heavy soils Fresh
  • sheep- and goat dung are good for heavy soils. They are the richest in organic material.
  • Poultry dung is good for heavy soils.
  • Composted dung is usually well-balanced and doesn’t require pre-composting like the aforementioned fresh dung.

Specific fertilizers for tomatoes, strawberries, vegetables, fruit trees, and roses….are adapted to a given plant or type of plant.

Roasted horn is a fertilizer for plants composed of organic nitrogen.  It’s a fertilizer that decomposes very slowly.

You can also find different organic fertilizing seeds like mustard, which can be sown in parts of your patch temporarily not in use.  You just need to turn the soil over before you plant flowers. Spinach is a natural fertilizer for plants in that it captures the nitrogen in the air. At the time of harvesting, cut it at the soil level and leave the roots.

Read More: What are the Benefits of Organic Fertilizer?

Organic fertilizers are decomposed slowly by the micro-organisms contained in the soil and will feed the plants little by little.  For a thorough treatment, they should be introduced into the soil in Autumn, so that they can start their slow decomposition in order to be ready for the return of Spring,  helped by the heat.

To guide you, here are the main basic ingredients that can be found in the composition of all commercialized fertilizers.


Nitrogen (N)

Nitrogen is the most important element for healthy leaf growth.  Bad growth and yellow leaves are a sign of a lack of nitrogen.

Phosphorous (P)

Phosphorous is a tonic that brings sturdiness and resistance.

Potassium (K)

Potassium helps flowering and improves the taste of fruit and vegetables.

Magnesium (Mg)

Magnesium is an element of chlorophyll.  Stains on the leaves are a sign of a lack of magnesium.

Iron (Fe)

Along with other trace elements, iron is vital to the construction of the vegetal parts of the plant.  Yellow leaves mean there’s a lack of iron.
Other elements, although in smaller quantities, are also important in the proper development of plants.

Using fertilizers for Plants

Besides dung, fertilizers exist in different forms to feed plants and vegetables but you should you some water or select liquid fertilizers:

  • Pellets, liquids, in stick or soluble forms.
  • Choose according to your needs – rapid action or long-term action.

Spring and Autumn are the best times to fertilize but follow carefully the instructions on the packet, as often fertilizer numbers can burn the plant.  You mustn’t put it directly on the leaves (except for leaf fertilizer), and fertilize on wet days or on days when the soil is wet so as not to burn the roots.  Avoid fertilizing very young plants, which are quite fragile.

It is essential to store fertilizer numbers out of the reach of children and domestic animals.

Ecological fertilizers

The technique of ecological fertilizing consists of putting leguminous or forage plants into the land which is left unused between two plantings.   They are then buried in the soil  – this captures the nitrogen in them and then feeds your plants.

This technique is used by gardeners who want to put a bit of new life back into the soil.

The leguminous and fodder plants are grown on a parcel of land left fallow between two plantings. They are then buried in the soil after flowering. The dense foliage, once buried, rapidly ferments and naturally increases the amount of organic material in the soil (humus and nitrogen).

This technique not only puts nitrogen into the soil, but it also improves the drainage of the soil and keeps the earth in place, preventing it from eroding, as the dense root system of the buried plants keeps the soil in place. The structure of the soil is thus improved physically, chemically, and biologically. Another advantage of this method is that it stops weeds from invading the area.  Sowing is usually done in Spring before the first plantings or in Autumn after harvesting.

Many different plants are used as ecological fertilizers. Which ones depend on the type of soil and on the needs of the plants to be grown? Generally, fodder and leguminous plants are used, like clover and burclover, or non-leguminous plants like mustard, phacelia, or vetches. Other plants like rape, buckwheat, rye, cabbage, ryegrass, and white lupin are also used.

Choose the type of ecological fertilizer for plants that best suits your soil :

white mustard, for example, grows quickly and is a natural insecticide.  Phacelia is also an efficient insecticide as well as being a good retainer of nitrogen – its dense, thin roots smother the weeds.  Fodder rape is nitrogen-rich but its strong roots make it difficult to bury.  Ryegrass (Italian or English) is ideal for fallow land as it protects the soil from erosion (though it tends to attract damaging insects).  Clover (crimson or red) is ideal for cruciferous plants like cabbage, turnips, and rape, as it is rich in nitrogen.


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