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Blue grain as fertilizer

Blue grain is probably one of the most popular types of fertilizer for our gardens and lawns. The chemical agent helps the plants with the supply of nutrients, which promotes growth. However, the use of blue grain is controversial because it is an industrial fertilizer and therefore has no place in an ecological garden. Especially gardens that are roamed by children or pets should not be fertilized with the nitrate-containing substance. But what is blue grain made of? How is it used to fertilize lawns and is it actually toxic? We give the important answers in our article on the topic.

blue grain

Blue grain as a panacea

Blue grain causes growth and is therefore an important helper for the hobby gardener. Many soils in our regions cannot provide the plants with enough nutrients for lush growth. For this reason, fertilizer is used in many places and the plants are supplied directly with nutrients.

Each gardener must decide for themselves whether blue-seed is necessary, as this depends heavily on the soil conditions. If there are no problems with the formation of flowers and the plants are lush green, fertilization is actually not necessary. In such a case, the chemical club can be dispensed with in the interest of the environment.

Ideally, a soil sample is taken and sent to a laboratory:

  • Take a soil sample in autumn
  • Dig holes in approximate places in the lawn
  • depth to the roots
  • Take samples, place in bucket and mix
  • Bottle 500 g and send to laboratory
  • Obtain information on shipping from the Chamber of Agriculture

The laboratory checks the soil for its nutrient content, so that the hobby gardener then knows whether he needs to support with blue grain or not.


Special suitability for evergreen plants

However, if the garden comes in rather pale tones and without flowers, blue grain can counteract this. The fertilizer contains minerals and trace elements that are directly absorbed by the plants through their roots. Due to the high concentration of nutrients, Blaukorn can only be used outdoors.

Use on potted plants indoors is only necessary and possible in exceptional cases, since the high dosage would destroy the sensitive root system of the potted plants. In the garden, however, the industrial fertilizer works wonders when it comes to growth and robustness. Evergreen plants in particular benefit from the nutrients, which is especially true for the lawn.

Evergreen plants include:

  • rhododendron
  • boxwood
  • laurel
  • yew


The lawn in focus

Since this article deals in particular with the treatment of the lawn with blue grain, we will take a closer look at the lush green at this point. In our regions, a lawn is considered beautiful if it shines in a lush green and is free of bare brown spots.

In addition, moss and weeds should not have a chance to disturb the growth of the fine blades of grass. For all these properties, Blaukorn is the perfect fertilizer straight from the lab. It is inexpensive to produce and takes effect after just a few days, so the gardener does not have to wait long for good results.

not affect soil properties

However, care must be taken to ensure correct application, as the floor changes its properties completely if the treatment is too long. In such a case, fertilizing is rather harmful, since weeds can then thrive perfectly on the nutrient-poor soil.

However, over-fertilization would also be problematic with organic fertilizer: Up to 400 earthworms can quickly romp about on a square meter of over-fertilized lawn with organic fertilizer, which feed perfectly on the plant remains in the fertilizer and then destroy the lawn roots. When it comes to blue grain, the motto "less is more" clearly applies, as we describe in detail in the section on correct use.


Fertilizer from the laboratory

A distinction is made between mineral and organic fertilizers. The blue grain is clearly a mineral fertilizer, as it is produced in the laboratory and contains no plant substances. Industrial fertilizer has the advantage that the concentration of nutrients is very high and results can therefore be achieved quickly. However, the disadvantage is the dosage.

If you fertilize too much, it will damage the lawn rather than help it. Blue grain is produced in the laboratory and has a bluish tint, hence the name. Half of it consists of pure nutrients, which further underlines the concentrated composition. The fertilizer can be bought in sacks by the kilo price.

The costs for the product can be staggered as follows:

  • 3 kilograms: 5 to 7 EUR
  • 15 kilograms: 20 to 30 EUR
  • cheap no-name products for less than 1 EUR per kilogram


The blue grain is also referred to as NPK fertilizer.

This is due to the ingredients of the fertilizer:

  • nitrogen (N)
  • Phosphorus (P)
  • Potassium (K)
  • if necessary magnesium (Mg) and sulfur (S)

However, the composition of the respective nutrients varies depending on the provider and variant. The standard product comes in the variants 12% nitrogen (as nitrate nitrogen and ammonium nitrogen), 12% phosphate and 17% potassium. In addition, 2% magnesium is part of the mixture.

Other combinations are therefore in the ratio 14+7+17+2 or 21+5+10+3+6. The latter product has an admixture of sulfur of 6%. Depending on the soil conditions, the hobby gardener should choose one of the variants in order to find the perfect additional fertilizer for the lawn.


Nutrient action on the lawn

Hobby gardeners will ask themselves what the three main components nitrogen (N), phosphorus (P) and potassium (K) actually stand for. Each of these nutrients has a unique effect on the lawn. Nitrogen, for example, serves as a growth engine and thus allows the grass to grow stronger. It is also responsible for a rich green color.

Nitrogen is the most important substance for appearances and a quick recovery from the outside. The phosphorus, on the other hand, takes care of the roots of the lawn. The phosphorus promotes root growth and tangles and provides energy for the lawn. The third nutrient, potassium, strengthens the lawn. It makes the blades of grass more resilient and strengthens them against diseases, cold or drought.

fertilizer time

The best time for fertilizing

The possible time for fertilizing extends over a period from March to October. However, it makes sense to supply the lawn with nutrients, especially in spring.

  • Fertilize the lawn from March to mid-May
  • look out for moderate weather
  • do not fertilize in the heat
  • Rain carries nutrients into the soil

If the lawn needs fertilizer in summer or autumn, you should definitely wait for a week with little sun, otherwise the lawn would burn. In addition, the evening hours during this time are chosen sensibly and sufficient watering afterwards is important.

apply fertilizer

We come back to the motto “less is more”. With the high concentration of blue grain, care must be taken to ensure a healthy dosage when applying. Due to the high salt content, it quickly happened that the soil became acidic and the roots of the lawn died off. Inexperienced gardeners can use a spreader so that a suitable dosage can be achieved without any problems.

This can be adjusted to spread fertilizer evenly across the lawn. The amount depends on the product and should be taken from the packaging. It is important that the fertilizing takes place on a dry lawn, which, however, must not be dried out. Then you should pay attention to rain or an alternative irrigation, so that the blue grain slowly dissolves and can seep into the ground.

Blue grain liquid

If you don't have a spreader at hand and don't dare to fertilize manually, liquid blue grain is recommended. This bottled remedy is diluted with water for use. The mixing ratios can be found in the respective product description. The liquid blue grain has advantages but also disadvantages compared to the granules.


  • better dosage
  • smaller storage area
  • cannot be picked by birds


  • mix before use
  • seeps in very quickly
  • more expensive

Rapid infiltration is certainly the biggest problem. It can happen that the important nutrients in the groundwater disappear without the root system of the lawn being able to benefit from it. This is the same reason why the granules should not be applied to wet lawns or during heavy rain. Too much moisture can cause problems.

Remove thatch

Sensible fertilization can only take place if the lawn has been completely freed from thatch. Thatch is a layer of dead grass or old clippings. This layer can be several centimeters high and prevents the fertilizer from seeping into the soil. In addition to the fertilizer, no air and only a little water can penetrate through the felt layer.

It is therefore important that the thatch is removed. This is done by scarifying. This work should be done once a year in March or April. A scarifier cuts the thatch out of the ground, but care must be taken not to attack the turf itself. The scarifier can easily be borrowed from a hardware store.

Do the lawn good

In addition to fertilizing with blue grain, the hobby gardener can also do something good for his lawn in other ways. The alternatives are briefly presented here. The simplest form is watering. Lawn grass consists of 90% water and therefore this is essential for life. Gardeners make sure there is sufficient moisture around the root system.

To do this, water the lawn regularly in the mornings and evenings during hot and dry phases. Another option is ventilation. Certain devices comb through the blades of grass and thus ensure that they do not get caught with each other. A third option is to regularly remove weeds. Hobby gardeners are doing their lawn a favor by constantly removing weeds as soon as they start to spread.

Blue corn is poisonous

danger to humans?

Finally, we have to deal with an aspect that critics of blue grain rightly raise again and again: Is the fertilizer from the chemical laboratory poisonous or not? In short, the blue grain is a chemical club that contains no natural substances. It consists of high doses of nutrients that the human body does not need.

  • Nitrogen nitrate causes irritation of the stomach and intestines in the body
  • The consequences are vomiting and diarrhea
  • Nitrate can be converted into nitrite
  • nitrite binds less oxygen to the red blood cells, which means that the whole body is undersupplied

Ultimately, however, only the quantity is decisive. A grain of granules will by no means cause the symptoms described above. However, problems can also arise with small quantities and should be observed.

Protect children and pets

Since children and pets have a significantly smaller physique, even smaller amounts are dangerous for them. Blaukorn should therefore under no circumstances get close to these vulnerable people. It should not be used in the garden if there are children or pets there. If they eat blue grain, a doctor should be consulted in an emergency.

The problems that can arise from nitrite poisoning should not be underestimated. The environment can also suffer from blue grain, since soils become acidic as a result. It is therefore important to ensure that not too much fertilizer is used. Acidic soil burns plants and destroys vegetation.

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