NPK fertilizers are considered an all-round talent when the vegetables in the garden are weak. Very few hobby gardeners know that they damage their plants and the soil in the long run. It is very important to understand how these fertilizers work. Organic alternatives are better.

NPK fertilizer provides plants with everything they need, but poses an environmental problem

Table of Contents

Show all
  1. the essentials in brief
  2. Explanation
  3. areas of application
  4. toxicity
  5. Self made
  6. correct dosage
  7. advantages and disadvantages
  8. frequently asked Questions

    9. the essentials in brief

    • NPK fertilizer consists of mineral salts. The main components are nitrogen, phosphorus and potassium. Plants need these nutrients for healthy growth.
    • When used properly, NPK fertilizer is not dangerous. Its toxic effect on humans, animals and the environment occurs when used improperly.
    • You can make your own NPK fertilizer, although organic alternatives make more sense. Due to their rapid availability, NPK fertilizers must be dosed precisely so that the advantages outweigh the disadvantages.

    What is NPK fertilizer?

    The core nutrients of a complete fertilizer are nitrogen, phosphate and potassium. Such compositions are also referred to as NPK fertilizers, which is derived from the symbols of the chemical elements. How high the concentration of the individual nutrients is is given in percentages.

    Contents on the NPK fertilizer: composition

    Information on the packaging of the NPK fertilizer such as 15-15-15 or 10 52 10 states that the fertilizer contains either 15 percent each of nitrogen, phosphate and potassium or 10 percent nitrogen, 52 percent phosphate and 10 percent potassium. If another number is listed, it indicates the magnesium content.

    What plants need:

    • nitrogen: promotes the growth of the green parts of the plant
    • phosphorus: supports the development of flowers and fruits
    • potassium: regulates the water balance and strengthens the plant tissue

    This is what an NPK fertilizer brings: application

    NPK stands for nitrogen (N), phosphorus (P) and potassium (K)

    The composition provides information about the possible uses of the fertilizer. They give the plant everything it needs to grow. The complete fertilizers can be used both for basic supply and for top-up fertilization. The mixtures are spread by hand or added to the irrigation water. An oversupply of individual components can adversely affect growth.

    nitrogen

    Plants need this element for healthy growth. Nitrogen is a component of the plant pigment chlorophyll and proteins. In a gaseous state, it makes up 78 percent of the air, whereby plants can only take up nitrogen in the form of nitrate or ammonium ions. This happens through the roots, which is why special fertilizers are administered to the soil. NPK fertilizers for lawns are nitrogen-rich and are mainly applied in the spring. A nitrogen deficiency is noticeable by light green leaves and an oversupply by blue-green leaf mass.

    phosphorus

    To prevent permanent irreversible plant damage, you should give your plants phosphorus. Phosphorus-rich fertilizers are used where the plants do not flower well or where the undersides of the leaves are reddish. They are mainly intended for beds and hedges with flowering ornamental plants and balcony flowers. However, the soil has an impact on how much phosphorus a plant can absorb. Plants have a harder time absorbing the element if the soil is too moist, compacted or the pH is too low. An overdose of phosphorus will result in poor growth.

    potassium

    If the leaves of your ornamental plants are hanging limp despite a good water supply, this may be due to a potassium deficiency. Reach for a high-potassium complete fertilizer. Herbs and green plants need more potassium and nitrogen. Their need for phosphorus is lower because flower development is not important for them. Heavy-growth vegetables produce higher yields when adequately supplied with potassium. Overfed plants often develop brown leaf edges.

    Can I use NPK fertilizer in the aquarium?

    Aquarium plants also need these nutrients for healthy growth. When choosing, you should make sure that the complete fertilizer is suitable for the aquarium. Which fertilizer you choose also depends on your water parameters. Often there are nutrients in the starting water that get into the water through feeding or stocking. Existing nutrients should no longer be administered.

    How to fertilize the aquarium:

    1. Measure water values such as iron, nitrate and phosphate
    2. Select complete fertilizer (NPK), mixed forms (PK, NP, NK) or individual components (N, P or K) according to the values
    3. Adjust nutrient concentration to the tank
    4. Bring other water parameters such as CO2 and light into the optimum range

    Is NPK fertilizer toxic?

    Heavy metals play a role in human health; they are absorbed from the soil by plants and thus enter the food chain. These elements are toxic in high concentrations, but plant organisms and humans both need essential trace elements for important metabolic processes. Some NPK fertilizers can contain additional trace elements in addition to the main nutrients, which is why you should pay attention to the exact composition.

    NPK fertilizer is toxic if used improperly.

    blue grain

    Blaukorn is also an NPK fertilizer

    These blue-colored beads also belong to the NPK fertilizers. In addition to the main nutrients, blue grain also contains magnesium and sulfur, with the concentrations of the individual substances varying depending on the recipe. This complete mineral fertilizer is chemically produced and, like comparable NPK fertilizers, can cause various problems.

    Toxic - for animals

    If pets accidentally eat the blue-colored grains from the bed, this can lead to health problems. Consumption leads to bloody diarrhea, salivation or vomiting as well as shortness of breath and tremors. The cycle can collapse, which in the worst case ends fatally.

    If you suspect your pet has eaten blueseed, you should monitor them and consult a veterinarian at the first symptoms. Be careful to keep the animal's airway open and do not attempt to induce vomiting. A possible treatment method is the administration of charcoal tablets to bind the toxins.

    Toxic - to humans

    The nitrate contained in NPK fertilizers is converted to nitrite in the plant or in the human body. In large quantities, this substance can lead to blue addiction. Small children in particular should not come into contact with the fertilizer. In blue addiction, there is an increased level of methemoglobin, which disrupts the oxygen supply. Drowsiness, confusion and headaches occur. In severe cases, coma-like states occur, which can be fatal. Blue addiction is treated with a blood transfusion.

    Toxic - for the environment

    Most garden soils are oversupplied with certain nutrients and do not need a complete fertilizer. Unused elements are washed out or accumulate in the soil. This affects the microorganisms in soil and water. Nitrogen is difficult to store in soil. If the element gets into the groundwater as nitrate, the way to drinking water is not far away.

    Consequences for agriculture:

    • Farming is concentrated on a few types of fruit, which are favored by mineral fertilizers
    • nitrogen-fixing legumes or undemanding crops are meaningless
    • further measures required to preserve the humus layer
    • less competitive plants and species from poor locations are pushed back
    • Biodiversity is lost

    Mix NPK fertilizer yourself

    Compost is a good alternative to NPK chemical fertilizers

    If you have a liquid fertilizer at home that does not offer the optimal nutrient concentration, you can mix it yourself with purchased individual components. However, it takes a bit of finesse to bring the individual substances into the desired ratio. Therefore, you should think about alternative organic fertilizers that are similar to an NPK fertilizer.

    tips

    Liquid fertilizers with a pH value that is too high can be neutralized with a dash of salad vinegar. Get a test strip to check the value.

    Produce organic fertilizers

    Such mixtures contain natural components that are decomposed by microorganisms in the soil. The nutrients are not immediately available to the plant, which reduces the risk of over-fertilization. Compost is an ideal fertilizer, the NPK concentration of which differs depending on the material being composted. Be careful what you throw into the compost and mix in animal substances if necessary.

    nitrogen phosphorus potassium Others
    banana peels - - x high content of magnesium
    nettles x - - Manure have a high pH value
    animal dung x x x in different concentrations depending on the animal species
    coffee grounds x x x contains minerals
    ash - x x has a strong alkaline effect

    Dose NPK fertilizer correctly

    How many nutrients a plant needs depends on the growth stage and soil conditions. Plants grown under controlled conditions in the greenhouse find it easier to achieve optimal nutrient levels than grown outdoors under fluctuating conditions. The following example shows which concentrations of NPK fertilizer the hemp needs in the individual growth phases.

    digression

    Hemp cultivation in Germany

    Cannabis can be legally purchased in Germany because it is considered a prescription drug for patients with chronic pain. However, the cultivation of hemp is illegal. The intoxicating herb can only be cultivated and harvested for a limited period with a special permit. Such special permits are issued for research purposes. Most of the medically used hemp products are imported. In the coming years, the demand for cannabis should be covered by German cultivation.

    vegetative phase

    Seedlings should only be given a small dose of NPK fertilizer

    Seedlings with one or two pairs of leaves require few nutrients. A concentration of 2-1-2 NPK is sufficient to stimulate plant growth. As the number of leaves increases, so does the need for nutrients. As soon as the young plants have developed five pairs of leaves, they are optimally supplied with a 4-2-3 fertilizer.

    The need for nitrogen then increases rapidly. Plants need a NPK concentration of 10-5-7 to promote vigorous growth. Only in the late vegetative phase does the nitrogen requirement drop by around 25 percent. Values of 7-7-7 are sufficient just before flowering.

    generative phase

    During the early flowering phase, hemp requires high levels of phosphorus, so NPK values of 5-10-7 are optimal. Subsequently, continuously increased concentrations ensure balanced growth, with the entire flowering phase being accompanied by a predominant proportion of phosphate. During the middle phase, concentrations of 6-15-10 are optimal. When the flowering period comes to an end, the nutrient requirement slowly reduces. NPK fertilizers with values 4-10-7 provide sufficient elements.

    advantages and disadvantages

    NPK fertilizers are convenient but harmful to the environment

    NPK fertilizers are extremely convenient. They ensure improved growth in the short term when deficiency symptoms occur. Therefore, such products are used not only in agriculture, but also in the private garden when growing vegetables. The plants are fully supplied and can absorb the nutrients directly from the soil without having to first make them available through microorganisms. Compared to organic alternatives, NPK fertilizers are cheap. Blaukorn costs between one and four euros per kilogram.

    Disadvantages of improper use:

    • Ecological damage: unused nutrients get into the groundwater through leaching and pollute the soil
    • short-term: in the long run, the fertility of the soil and crop yields decrease
    • growth disorders: imbalanced nutrient concentration leads to bolting and prevents flower development

    tips

    To reap the benefits of NPK fertilizers, you should first conduct a soil test. If necessary, administer individual components and do without complete fertilizers.

    frequently asked Questions

    What types of NPK fertilizers are there?

    A mineral NPK fertilizer consists of inorganic substances. This is mainly made from water-soluble salts that are of synthetic origin. Complete fertilizers contain additional trace elements. The salts are offered in liquid or solid form. Organic NPK fertilizers are not actually NPK fertilizers. Their nutrients come from plant or animal raw materials. There is also an intermediate form called an organo-mineral NPK fertilizer. These consist of synthetic materials to which organic substances such as horn meal have been added.

    How much NPK fertilizer on 1 ha of grassland?

    How high the nutrient requirement of grassland depends on the cutting intensity and the types of grass present. Intensively used areas on which high-quality grass mixtures thrive have a nitrogen requirement of 240 to 300 kilograms per hectare. However, there are regulations as to how much NPK fertilizer may be applied. A maximum of 170 kilograms of nitrogen may be used on grassland per hectare and year. A soil analysis provides information about how much NPK fertilizer is required and in what concentration.

    What are the prices of NPK fertilizers?

    Prices vary depending on manufacturer and composition. A basic price per kilogram of between 80 cents and two euros is usual, with this price falling for larger purchase quantities. This means that mineral NPK fertilizers are significantly cheaper than organic alternatives. Here the price per kilogram varies between three and five euros. A self-made fertilizer from organic waste is free of charge.

    Examples of prices:

    • 25 kg of NPK fertilizer (15-15-15): approx. 22 euros
    • 50 kg NPK fertilizer (10-6-18): approx. 42 euros
    • 100 kg NPK fertilizer (15-10-10): approx. 95 euros

    Are NPK fertilizers harmful to health?

    Mineral fertilizers available in Germany must not have any harmful effects on health or the environment. Proper use is therefore of great importance. If fertilizers are not abused, they are considered harmless.

    Since NPK fertilizers consist of soluble salts, the dust on the skin or in the eyes combined with water can cause irritation or dehydration. Improper use such as consumption can cause damage to health. In order to protect children or pets, the fertilizer should always be worked into the soil and never stored in the open.

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