There are many phosphate fertilizers on the market. We will explain why a plant needs phosphate, what phosphate fertilizers are available and how they work.
Phosphates are the s alts of phosphoric acid (H3PO4) and are used for phosphorus fertilization. Phosphorus is vital for our plants and essential for the maintenance of many functions in the plants.
We know phosphorus from complex fertilizers, which usually contain phosphorus, but there are also pure phosphorus fertilizers. You can find out what our plants need phosphorus for and the differences in phosphate fertilizers in our article.
What do plants need phosphate for?
Phosphorus is mostly obtained from plants in the form of phosphate (H2PO4-and HPO42-) and required for various functions in the plant. This nutrient is essential and vital for your green darlings.
The main functions of phosphorus in plants are as follows:
- Forms important cell component
- Component of carbohydrates
- Component of DNA and RNA
- Important in building enzymes
How do you recognize a phosphate deficiency?
If the plant lacks phosphorus, this leads to various deficiency symptoms. Such deficiency symptoms usually appear first on the older leaves. These include the following symptoms:
- Inhibition and standstill of plant growth
- Rigid reed position, hence the name "rigid garb"
- Poor growth
- Dark to blue-green matte coloring
- Leathery and dirty green appearance
- Red discoloration of stems and veins
- Leaf fall and bare shoots
- Deficiency symptoms are often difficult to classify
Since the nutrient magnesium is also required for the transport and absorption of phosphate from the soil, a magnesium deficiency in the soil often results in a phosphate deficiency as well.
Also inhibit inacidic soils iron and aluminum absorb phosphate. If the soil is rich in lime, the calcium it contains leads to the precipitation of phosphates. Calcium phosphates are then formed, which are difficult to dissolve and can no longer be absorbed by plants.
Properties of phosphate fertilizer
Phosphate fertilizers supply plants mainly with the main nutrient phosphorus (P) in the form of s alts of phosphoric acid. Pure phosphorus is not very soluble in water, which is why it must first be processed before it can be used as a fertilizer. In the process, insoluble calcium phosphate is broken down with the help of various acids, making the nutrients available to the plants.
Phosphorus is mainly taken up by the plants via the roots, i.e. via the soil solution. Therefore, phosphate foliar fertilization is only suitable for covering short-term peaks in demand. At a pH between 6.0 and 7.0, the phosphate in the soil is most available to plants and most easily absorbed.
Effect of phosphate fertilizer
The phosphate fertilizer not only supplies plants with the nutrient phosphorus and thus prevents deficiency symptoms, it also has an effect on the soil.
If phosphate fertilization is too high, the nutrient can be leached into groundwater and bodies of water, causing impacts.
In the event that nutrients such as phosphorus accumulate in water, there is increased growth of aquatic plants and algae - this process is called eutrophication. When these aquatic plants die, they sink to the bottom of the water body and are microbially degraded there. However, this degradation requires a lot of oxygen and can lead to a lack of oxygen in the water. In addition, toxins can build up and the lack of oxygen can kill fish and other creatures in the water.
So be careful with phosphate fertilization, because garden soils in Germany are generally sufficiently supplied with phosphorus. However, if you want to be on the safe side, have a soil test carried out. This allows you to determine the nutrient content in your soil. In a soil analysis, different content classes of the soil are determined. The following values are found for phosphorus:
- A (low): 0 to 5 mg of phosphorus per 100 g of soil
- B (medium): 6 to 14 mgPhosphorus per 100g of soil
- C (high): 15 to 25 mg of phosphorus per 100 g of soil
- D (very high): 26 to 40 mg of phosphorus per 100 g of soil
- E (particularly high): over 40 mg phosphorus per 100 g of soil
Use and use of phosphate fertilizers in universal fertilizers
In universal fertilizers or complex fertilizers, phosphorus must not be missing, it is also a component of NPK fertilizers. There the phosphorus is present together with nitrogen and potassium.
Fertilizer with phosphate content
As already mentioned, the well-known mineral NPK fertilizers contain nitrogen, phosphorus and potassium. They differ in composition and in the proportions of the individual components. The phosphate content of these complex fertilizers is usually between 5 and 15% phosphorus.
There are also special dual-nutrient fertilizers that usually contain two of the nutrients nitrogen, phosphorus and potassium. A nitrogen phosphate fertilizer, also called NP fertilizer, contains around 20% phosphate. Another dual nutrient fertilizer is Thomasphosphat-Kali, which contains 10% phosphates. Thomas flour is also a phosphate fertilizer that consists of 15% phosphate and is a by-product of steel and iron production.
Fertilisers with a predominant phosphate content
Fertilisers with a predominant phosphate content are mainly used in agriculture. There is usually already enough phosphorus in our garden soil and such large doses are not necessary.
An example of a phosphate fertilizer with a high phosphate content is diammonium phosphate (DAP). This consists of nitrogen and phosphorus and forms light brown granules. DAP contains 46% highly concentrated phosphate, 41.5% of this phosphorus is water soluble. DAP is easy to store and transport because the fertilizer does not absorb water and therefore does not clump.
Monoammonium phosphate (MAP) is another granular fertilizer composed of nitrogen and phosphate. MAP can also be dissolved in water and contains approximately 52% phosphate. MAP can also be stored optimally and also does not tend to clump.
A well-known group of phosphate fertilizers are the superphosphates, which differ in their phosphate content and composition. Calcium phosphate and sulfuric acid are used to produce superphosphate. The resulting fertilizer contains 16 to 22% phosphate. However, there is also double superphosphate, which contains 35% phosphate, andTriple superphosphate that even contains 46% phosphate.
Phosphate in NPK Organic Fertilizers
In addition to nitrogen and potassium, organic compound fertilizers also contain phosphorus. Of course, the phosphate content in organic fertilizers is lower than in mineral ones. Nevertheless, one should not overdo it with phosphate fertilization and use this nutrient responsibly. Our Plantura organic fertilizers also belong to the complex fertilizers, which mainly consist of plant-based raw materials.
In addition to components such as vinasse or wheat gluten flour, Plantura organic fertilizers also contain rock phosphate, which ensures a long-term supply of phosphorus to plants and soil. Our Plantura organic tomato fertilizer and our organic universal fertilizer contain 3% phosphorus, while Plantura's organic flower fertilizer contains 2% phosphorus. Plantura's organic lawn fertilizer and our Plantura autumn lawn fertilizer contain 1% phosphorus. So if you rely on the organic fertilizers from Plantura, then you also rely on a deliberately chosen lower phosphate content, which is completely sufficient. In this way you activate soil life and promote nutrient availability in the soil.
Phosphate in mineral NPK fertilizers
In the mineral complex fertilizers you can of course also find phosphorus. The advantage of such fertilizers is that the nutrient concentration is precisely known and the phosphorus is available more quickly than in organic fertilizers. Unfortunately, the mineral fertilizers contain too much phosphate compared to the amount required. Finally, as mentioned earlier, overdosing on mineral fertilizers always carries the risk of pollution and eutrophication of water bodies. Therefore, you should always follow the manufacturer's dosage instructions meticulously. You should also take care of your own he alth when using mineral fertilizers, as they can cause he alth problems such as skin irritation. You should therefore always make sure that you have the necessary personal protective equipment when using mineral fertilizers.
Are you unsure which fertilizer is the right one for your garden? We'll help you decide.