In this article you will learn why plants need phosphate, which phosphate fertilizer you can apply when and how - and why these fertilizers are problematic, especially when used in agriculture.

Phosphate fertilizers should be used with great caution

Table of Contents

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  1. the essentials in brief
  2. What is phosphate fertilizer?
  3. Effects and Effects
  4. Types of phosphate fertilizers
  5. correct application
  6. frequently asked Questions

    7. the essentials in brief

    • There are numerous phosphate fertilizers with different levels of phosphate between 5 and 52 percent.
    • They should only be used if there is a proven phosphate deficiency in the soil or plants.
    • Phosphate fertilizers contain heavy metals such as cadmium and chromium, which are deposited in plants, animals, soil and groundwater.
    • A soil analysis must be carried out before application, and the dosage can be reduced by adding stable manure.

    What is phosphate fertilizer?

    Phosphorus (P), together with nitrogen (N) and potassium (K), form the three main nutrients that are vital for plant growth and are therefore the most important components in every complete and NPK fertilizer. Sometimes there can be a lack of phosphorus, which significantly impairs flowering and fruiting as well as the healthy growth of ornamental and useful plants. In this case, a special phosphorus fertilizer can help.

    Phosphate fertilizers consist of the salts of phosphoric acid (H3PO4). Since pure phosphorus is poorly soluble in water, it must first be chemically processed before it can be used as a fertilizer. Various acids break down the required calcium phosphate. Only then are the nutrients available for plants.

    composition and properties

    "Globally, more uranium is extracted from phosphate mines than is used in nuclear reactors."

    Crude phosphorus is mined in huge mines

    The raw phosphorus required for phosphorus fertilizers is mostly obtained by mining from natural deposits that have formed from deposits of former marine animals millions of years old. Many of these deposits are located in the countries of North Africa, as well as in South Africa, Jordan, China and Russia. The world's largest phosphate producer is Saudi Arabia. Rock phosphate is also obtained from the remains of seabirds, the so-called guano.(121.99€)

    The plants take up the processed phosphorus through their roots, with the fertilizer being best available at a pH between 6 and 7. Various phosphorus foliar fertilizers are commercially available, but they only help in the short term - the lion's share of the nutrient is eventually absorbed by the roots.

    digression

    Thomas flour - an inexpensive, but problematic phosphate fertilizer

    So-called Thomas flour is a very cheap phosphate fertilizer which, however, should not be used due to its high proportion of the heavy metal chromium - the heavy metal accumulates in the soil and in the plants and also gets into the groundwater. Thomas flour is a waste product from iron ore smelting and is therefore highly contaminated.

    Effects and Effects

    Phosphorus is an important component of every plant cell. The element is essential for the functioning of the metabolism in all ornamental and useful plants. A phosphorus deficiency, detected either by growth depression in plants or, more commonly, by soil analysis, should therefore be corrected immediately. The use of a phosphorus fertilizer when applied correctly has the following effects:

    • Roots grow deeper, so the plants can be better supplied
    • the formation of buds and flowers is supported
    • Support of cell division and thus leaf and shoot growth
    • Supporting resistance to diseases and pests

    In order for the phosphorus fertilizer to work optimally, you should before using it

    • conduct a soil analysis
    • and apply the phosphorus fertilizer only if the analysis has revealed a deficiency
    • then do a pH test

    If the soil is too acidic (pH value below 5.5), it should first be brought into the optimal range between 6 and 6.5 by liming. If the result is more than 7, you better choose a water-soluble phosphate fertilizer.
    But be careful: phosphate fertilization not only affects the plants, but also directly affects the soil and groundwater. Too high a proportion of phosphate in water can be recognized by excessive algae growth, and aquatic plants and aquatic creatures such as fish, snails, mussels and crabs die due to the lack of oxygen. This effect can often be observed in water bodies located in heavily agricultural regions. Therefore, phosphate fertilization should only be carried out if it is really necessary.

    digression

    Caution, highly toxic!

    Phosphate fertilizers contain highly toxic components

    It is true that phosphate fertilizers are indispensable, especially in industrial agriculture, in order to achieve the highest possible yields. However, these fertilizers are also highly problematic, as they are heavily contaminated with toxic heavy metals, especially uranium and cadmium. By using such a fertilizer, these toxins inevitably get into our food via plants and animals. There is currently no legal maximum content of uranium in Germany, only a recommendation from the Federal Ministry of Food and Agriculture. The maximum value here is 50 milligrams of uranium per kilogram of phosphate fertilizer.

    Types of phosphate fertilizers

    Numerous phosphorus fertilizers are available on the market especially for home and hobby gardens. In addition to pure phosphorus fertilizers, you can also choose complex fertilizers with a high phosphorus content. Typical examples are universal or complete fertilizers as well as NPK fertilizers, because the three main nutrients nitrogen, phosphorus and potassium form the most important and therefore quantitatively largest components in these products.

    The following table provides you with an overview of common single and multi-component fertilizers.

    fertilizer type phosphate content Special properties price
    superphosphate 18 percent water-soluble granules, with NPK approx. EUR 1.10 per kilogram
    Superphosphate with Sulfur 18 percent water-soluble granulate, also contains sulphur approx. EUR 3.40 per kilogram
    Phosphate potash / Thomaspotash 8 percent Potassium fertilizer with a high proportion of phosphorus, as well as magnesium and other trace elements approx. EUR 2.10 per kilogram
    Dehner phosphate potash fertilizer with long-term effect 15 percent PK fertilizer with magnesium and sulfur approx. EUR 1.30 per kilogram
    P 20 liquid phosphate fertilizer 20 percent Concentrate to be diluted with water, also suitable for foliar application approx. 4 EUR per 100 milliliters
    Phosphorus Plus liquid fertilizer 7 percent Additional fertilizer with phosphorus and potassium for flowering plants approx. EUR 13.50 per liter
    Thomaskali 8 percent granulated PK fertilizer with magnesium approx. 0.90 cents per kilogram

    For home and hobby gardens, multi-component fertilizers that contain both phosphorus and other nutrients are usually perfectly adequate. Phosphate fertilizer with a very high phosphate content, for example

    • Diammonium phosphate (DAP) with 46 percent phosphate content
    • Monoammonium phosphate (MAP) with 52 percent phosphate content

    on the other hand, they are primarily used in agriculture. If you need a fertilizer with a high phosphate content for your home garden, it is better to choose what is known as superphosphate. This contains calcium phosphate and sulfuric acid, with the phosphate content varying between 16 and 22 percent depending on the manufacturer.

    correct application

    If the phosphate fertilizer is not used properly, it can have serious consequences

    Phosphate fertilizer requires proper handling in order to avoid possible overdoses and thus unnecessary exposure to heavy metals. It is not just a matter of the correct, needs-based dosage, but also the time and manner of application.

    time

    When you carry out the phosphate fertilization depends primarily on the specific product that you want to apply:

    • Water-soluble phosphate fertilizers: such as B. Superphosphate come as basic fertilizer in the spring on the ground. Choose granulated fertilizers as they release faster.
    • Phosphate fertilizer with a high proportion of rock phosphates: are applied in autumn. They are particularly suitable for acidic soils / soils with a low pH

    Liquid fertilizers containing phosphate are practical because you simply add them to the irrigation water and water the plants directly with them. You can also use these during the growing season.

    Dosage and Effects

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    Phosphate fertilizers should be applied as close as possible to the roots, as they only have an effect here. In contrast to nitrogen fertilization, however, you do not have to worry about damage to the roots. And this is how it is fertilized:

    • Follow the manufacturer's instructions regarding dosage and application.
    • However, the dosage also depends on the specific phosphate content of your garden soil.
    • About 30 to 60 milligrams of phosphate fertilizer per square meter are recommended for superphosphate.
    • Sprinkle the phosphate fertilizer directly onto the root disk of the plant to be fertilized.
    • Larger areas, such as lawns, fertilize evenly with the help of a spreader.
    • Work in the granules superficially.
    • Water vigorously to allow the fertilizer to dissolve and soak into the soil.

    Lower the dosage by applying organic fertilizer in the form of compost or manure at the same time. Stable manure in particular allows the amount of fertilizer to be reduced by up to 40 milligrams per square meter. When using compost, you need 15 milligrams less phosphate fertilizer per square meter.

    frequently asked Questions

    Are there alternatives to phosphate fertilizer?

    Manure is a great alternative to phosphate fertilizer

    Yes, fertilize your garden with manure. This contains a high proportion of natural phosphate (similar to sea bird manure), but some gardeners also need to get used to it. Please note that poultry manure in particular must be well rotted before you apply it! Otherwise, agronomists all over the world are researching to discover alternatives to mineral phosphorus fertilizers - this is about time, because the global phosphorus deposits are gradually coming to an end.

    Do you need special phosphorus fertilizers in the garden at all?

    No, the use of phosphorus fertilizers in home and hobby gardens is - with the exception of a deficiency confirmed by a soil sample - practically superfluous, especially if the garden is mainly fertilized with manure and compost. Many supposed signs of a lack of phosphorus in plants can also be traced back to other causes, which is why you should refrain from fertilizing if possible simply because of the high proportion of pollutants.

    How do I carry out a soil analysis?

    Since fertilization should not be carried out on suspicion if there is a suspected phosphorus deficiency, a soil analysis must be carried out beforehand. Of course, you don't do this yourself. You take soil samples from different places in your garden and send them to a specialized institute for soil analysis. You will then receive an evaluation and fertilizer information.

    tips

    If the growth of algae in the aquarium or garden pond gets out of hand, an excessively high phosphorus content could be to blame. You can easily determine this with a commercially available phosphate water test. If there is a phosphate load, a so-called "PhosphateMinus" product can help.

Category:

Vegetable garden