Phosphorus (P) ranks right after nitrogen (N) and even before potassium (K) as one of the vital elements for the growth of plants. Therefore, NPK complete fertilizers mainly contain these 3 elements to supply your ornamental and useful plants. If nitrogen and potassium are available in sufficient quantities while there is a lack of phosphorus, a special phosphate fertilizer solves the problem. This information illuminates in detail what the suppliers use to produce the single nutrient fertilizer, which types are available for purchase and which prices are charged. You can find out what effect you can achieve with phosphate fertilization here.


Anyone who cultivates their home garden in harmony with nature will not buy a phosphate fertilizer ad hoc on the basis of melodious promises made by the manufacturer. Rather, the main questions are which ingredients the suppliers use to manufacture the special fertilizer, whether they are toxic or harmless to human health. We looked over the shoulders of the producers and gained the following information about the composition:

The main nutrient, phosphorus, cannot be directly absorbed by the plants. In nature, the vital element is mainly contained in the salts of phosphoric acid, the phosphates. Raw phosphates have formed in different parts of the world over the course of many millions of years, as huge amounts of phosphorus-containing marine animals have been deposited there. Furthermore, phosphates are contained in the excrement of sea birds. Thus, phosphate fertilizer is essentially a natural product. Central deposits are in North Africa, Jordan, Russia, China, South Africa and the United States. The world’s largest producer of phosphate is Saudi Arabia.

The phosphate-containing Thomas meal that occurs during iron ore smelting is viewed very critically as a fertilizer. Due to the high exposure to the heavy metal chromium, environmentally and health-conscious hobby gardeners no longer buy the fertilizer, regardless of the low prices.

Symptoms of Phosphorus Deficiency

In principle, good garden soil contains a natural amount of phosphorus that is completely sufficient for the supply of your plants. However, plant availability can be impaired under the influence of various soil factors. The main factors to be mentioned here are moisture content, crumb structure, pH value and temperature. If there is an imbalance here, this inhibits the absorption of phosphorus. The following symptoms indicate a deficiency in this nutrient:

  • Inhibition of growth up to a complete standstill
  • Reduced flowering and fruiting
  • Roots no longer grow in depth, but in width
  • Reddish to purple discoloration and death of the older leaves
  • Typically a rigid attitude of the shoots and leaves (rigid costume)

First of all, it is the older leaves that show the symptoms. Fatally, at the same time, the young leaves take on a deep green color, which suggests an optimal supply of nutrients. Overall, the plants are subject to an unmistakable growth depression that leads to death if the deficiency in phosphorus is not compensated for.

Only rarely are growth depressions clearly due to an insufficient supply of phosphate. Only a professional soil analysis provides proof that the administration of phosphate fertilizer actually eliminates the problem.


The element phosphorus is part of every plant cell, stabilizes the DNA and plays an important role in the metabolism. The nutrient is therefore indispensable for the control of all life processes in your ornamental and useful plants. If you have identified the need for phosphate fertilization based on the symptoms mentioned or based on a soil analysis, the fertilizer has the following effects:

  • Strengthening the root growth in depth
  • Supports bud and flower formation
  • Forcing cell division and thus the growth of leaves and shoots
  • Improving disease resistance

The effect of phosphorus fertilization depends largely on the pH value in the soil. Plants are optimally available at a pH of 6.0 to 6.5. It is therefore advisable to carry out a pH value test before using the fertilizer. If the result indicates an acidic soil value of less than 5.5, first establish the ideal value with liming and only then apply the phosphate fertilizer. With a slightly acidic, neutral to slightly alkaline pH value greater than 7.0, buy a water-soluble phosphorus fertilizer.

Toxic by nature

When used properly, phosphate fertilizer is indispensable for promoting plant growth and achieving the desired yields. In this context, however, it should not be overlooked that mineral phosphorus fertilizers consist of contaminated rock phosphates. In addition to the desired nutrients, it also contains toxic heavy metals, primarily cadmium and uranium. The natural phosphate deposits were often initially used to break down these highly toxic heavy metals.
Numerous industrialized countries have now set a limit value for cadmium in phosphate fertilizers of 50 milligrams per kilogram of fertilizer, which is rarely fallen below. With regard to uranium, the Federal Ministry of Food and Agriculture currently has a recommendation to limit the limit to 50 milligrams per kilogram of phosphate fertilizer. With intensive fertilization, the heavy metals enter our food chain via plants and animals.

Varieties and prices

The market is well stocked with phosphate fertilizers for home gardeners, organic gardeners and farmers. As our short excursion into the effects of these special fertilizers shows, the pH value in the soil primarily determines which product variant is recommended. The following selection would like to give you a better overview:

  • Superphosphate with NPK 0-18-0 as water-soluble granules at a price of 8.95 euros per kg
  • Phosphorus liquid fertilizer with NPK 2.5-10-2.5 for watering and spraying at a price of 6.95 euros per 250 ml
  • Eco DCM phosphorus fertilizer with NPK 4-23-0 at a price of 1.93 euros per kg
  • Vivos phosphorus fertilizer for lawns and golf courses with NPK 4-30-0 at a price of 1.77 euros per kg
  • Hesi phosphorus fertilizer for flowering plants with NPK 0-7-5 at a price of 4.90 euros per liter
  • Diammon phosphate with NPK 18-46-0 in water-soluble form at a price of 4.11 euros per kg
  • Dolophos rock phosphate with NPK 0-15-0 (+2 magnesium) at a price of 4.52 euros per kg

Then there is a sensible alternative to mineral phosphorus fertilizers. The innovative Phosphatovite consists of natural silicate bacteria that make all the phosphate reserves in the soil available for your plants within 30 days. With a price of 65 euros per liter, the ecological product appears to be quite expensive at first glance. However, 0.5 liters are sufficient for 1 hectare.

Tips for proper use

Although producers make phosphate fertilizers from natural products, an overdose can be toxic to your ornamental and useful plants due to the heavy metal load. In contrast to organic fertilizers such as compost and plant manure, the focus is on the competent use of the special mineral fertilizer in an appropriate amount. The right time plays a role so that the desired benefits for plant growth take full effect. The following tips aim to draw your attention to relevant aspects:


In garden centers and hardware stores there are usually water-soluble phosphate fertilizers on the shelves, as they can be used in this form on almost all normal garden soils. Granulated, the surface is smaller than conventional fertilizer grains, which counteracts a too rapid release. Common products such as superphosphate or Vivos phosphate fertilizer are ideally applied in spring as basic fertilization in order to develop their potential in proportion to growth. In contrast, preparations that are difficult to dissolve, such as rock phosphate, hit the ground in autumn, which guarantees sufficient digestion until the next vegetation period, especially in acidic soil.

Dosage and application

Phosphate fertilization has the advantage that it can be applied in close proximity to the roots. In contrast to nitrogen fertilizers, there is no significant risk of damage from salts. How to do it right:

  • In spring, sprinkle the phosphate fertilizer directly onto the root disc on slightly moist soil
  • A dosage of 30 to 60 mg per square meter z. B. with superphosphate is recommended
  • Work in the granules on the surface and pour in

You can significantly lower the recommended dosage by administering an organic fertilizer at the same time. The addition of compost reduces the amount by 15 mg per square meter, while manure allows you to reduce the phosphate fertilizer by up to 40 mg per square meter.

Alternatives are in the starting blocks

The natural phosphate stocks are running out. Before there is no longer any oil, all sources of phosphorus will have dried up. Producing the nutrient synthetically, as is possible with nitrogen, cannot be realized. Scientists around the world are trying to find a way out of this mess. A symbiosis of plants and fungi, such as is common in orchids, for example, has now moved into the center of interest. After all, around 80 percent of all land plants can enter into such a ‘marriage’.

Mycorrhizal fungi that grow underground socialize with a plant by absorbing the phosphates hidden in the soil and passing them on to the roots. For this service, the plants reward them with sugar, which is available during photosynthesis. The researchers now want to find out whether the profitable community produces the same effects on all plants. These findings have already flowed into special mycorrhizal products that are being tested in organic farming. The future will show to what extent the symbiosis can play a role in the supply of nutrients to all crops and thus ensure the nutrition of the world population.

Home gardeners rarely see themselves prompted to buy a special phosphate fertilizer. This measure can only be considered if a professional soil analysis or unmistakable symptoms indicate a lack of phosphate. If the nutrient deficit is compensated for, growth depressions are resolved in no time at all, flowers unfold in all their splendor and the harvest once again meets all expectations. The downside in this interaction is that although phosphate fertilizers are natural products, they are contaminated with heavy metals. Cadmium and uranium cannot be eliminated during manufacture and, if overdosed, enter the food chain via the plants.

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