A fertilizer is an inorganic salt

Fertilizers are substances that are added to crops and promote their growth. The German chemist Justus von Liebig found out in the 19th century that the growth of plants is directly dependent on the supply of mineral salts. Liebig carried out a legendary experiment: he glowed plant remains in a porcelain crucible until only their ashes were left. When examining the ashes, the chemist found residues of salts of these trace elements: nitrogen, phosphorus, potassium, sodium, calcium, magnesium, iron and copper.

Salts, which contain nitrogen, phosphorus and potassium atoms, are particularly important for the growth of plants. Plants need these for their metabolism to build up proteins, enzymes or chlorophyll.

Many soils today are poor in nitrogen and therefore have to be fertilized with nitrogen-containing salts. Fertilized plants grow faster and give greater crop yields. Nitrates such as ammonium nitrate, which can be obtained from ammonia and nitric acid, are particularly suitable as fertilizers because they contain chemically bound nitrogen. The Haber-Bosch process is the most important process for producing fertilizers. The use of fertilizers can significantly increase the harvest yield per hectare of land.
However, if the fertilizer is used too intensively, there is a risk of over-fertilization of the soil. This leads to an accumulation of nitrates and phosphates in vegetables and in the groundwater. Since the algae in the waters also need nitrogen and phosphorus salts as nutrients, it can lead to an excessive multiplication of algae, an eutrophication, the water is deprived of oxygen due to an acceleration of the putrefaction processes and it tips over. The excessive supply of nutrients in a body of water leads to it only to temporary growth and ultimately to species extinction. Through the targeted use of fertilizers and above all through the consistent implementation of organic farming, the pollution of the waters can be reduced considerably.
The inorganic Mineral fertilizers are divided into different groups based on their ingredients and their area of ​​application. The trace elements that are most frequently taken in are nitrogen, phosphorus and potassium.
Nitrogen fertilizerLime ammonium nitrate (mixture of lime and ammonium nitrate); Calcium cyanamide (with calcium cyanamide) or urea
Phosphate fertilizer“Superphosphate” (mixture of calcium dihydrogen phosphate and calcium sulfate); "Thomas flour" (phosphate-containing mixture occurring during steel production)
Potash fertilizerKainite (potassium salt), potassium chloride, potassium sulfate
Lime and magnesium fertilizersCalcium carbonate, calcium oxide, dolomite, magnesium sulfate
Compound fertilizerComplete fertilizer with a combination of nutrients, example: The word Nitrophoska is made up of the words Nitrogenium (Latin: nitrogen), phosphorus and potassium
Organic fertilizer are made from vegetable and animal waste. Soil animals and microorganisms form the nutrient-rich humus from this waste. In the compost heap, the waste is converted into humus-rich fertilizer in a rotting process within a year. Compost and organic fertilizers contain significantly fewer trace elements compared to mineral fertilizers. The harvest yield for a hobby gardener is therefore not as large as with the use of mineral fertilizers, but the soil is loosened and the fertilization has a lasting effect. In addition, there are fewer residues in vegetables in organic farming.
The dried excrement of seabirds used as nitrogen fertilizer is called guano. Guano was already used as a fertilizer by the Peruvian Indians. He first came to Europe in 1804. Well known in agriculture slurry consists mainly of liquid animal excrement. It is particularly suitable as a fertilizer because of its urea content. Manure is a mixture of droppings and straw. The waste is not only suitable as a fertilizer, but is also used to generate energy in biogas plants.
additional Information
How a biogas plant works
Eutrophication of a body of water