Nitrogen fertilizer

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Nitrogen fertilizers are fertilizers that mainly provide the plants with their main nutrient element nitrogen . These fertilizers can be of natural origin (e.g. as potassium nitrate ) or manufactured by industry.

history

Traditionally, nitrogenous fertilizers such as liquid manure and manure are used in agriculture . After Justus von Liebig had discovered the importance of the chemical element nitrogen for yields in agriculture, the corresponding demand for fertilizers increased. Naturally occurring deposits contain potassium nitrate and sodium nitrate , for example in Chile (hence the common name Chilesalpeter ), and were mined mainly in the first half of the 19th century. The Haber-Bosch process , for which BASF applied for a patent in 1910 , succeeded in artificially producing ammonia as a starting material for the manufacture of fertilizers. The large-scale industrial production of mineral fertilizers made possible by this process made the immense growth of the world population in the 20th century and thus also modern society possible. However, the application of nitrogen fertilizers also increased mortality in butterflies . In addition, sewage sludge was used as a fertilizer in the 20th century , as it can contain up to five percent nitrogen in the dry matter .

term

Since nitrogen is considered the "engine of plant growth", it is the most important form of fertilizer. A distinction is made between mineral and organic forms of fertilizer. Plants mainly take up nitrogen as nitrate , ammonium and urea can also be taken up directly. Mineralization (breakdown of organic matter by microorganisms ) converts all nitrogen compounds in the soil into nitrate.

For reasons of environmental protection (nitrate leaching) and health (nitrate content), the principle of needs-based fertilization must apply to the nitrogen supply of crops. The necessary amount of nitrogen from fertilization is the difference between the nitrogen requirement of the respective crop minus the supply of the soil. The nitrogen supply is the supply of mineral nitrogen at the beginning of the cultivation - in the soil layer used by the cultivated plant - and the subsequent delivery during the cultivation period. Subsequent delivery takes place through organic matter ( humus and harvest residues) and natural nitrogen input (e.g. precipitation). It is therefore necessary to determine the nitrogen content at the beginning of a culture and possibly also during its course, but at least once a year as part of a soil survey .

use

Every year around 120 million tons of nitrogen are converted into reactive forms by fertilizers in intensive agriculture , more than is converted by the natural processes of the earth. These can get into water bodies and ecosystems and have a changing influence on them. If the nitrogen compounds are not bound to soil particles, they can quickly be leached into the groundwater or watercourses through precipitation. This is especially true for nitrate. Under reducing soil conditions (waterlogging), gaseous nitrogen losses can occur (N 2 , N 2 O, NO), at high pH values ​​also as ammonia (NH 3 ). In addition, part of the nitrogen fertilizer is converted into laughing gas, which is a powerful greenhouse gas that drives global warming . According to scientists, the acceptable limit for global ecosystems is 35 million tonnes of nitrogen input per year. The industrial production of nitrogen fertilizers takes place predominantly using fossil fuels and is responsible for 1.2% of global primary energy consumption .

The process of fertilizing

Calcium nitrate with 15.5% total nitrogen , of which 14.4% nitrate nitrogen and 1.1% ammonium nitrogen

Inorganic and organic nitrogen compounds from natural sources or from synthetic processes ("artificial fertilizers", see mineral fertilizers ) are used as fertilizers . The nitrogen content is given as the mass fraction of N (% N).

Some plants can use symbiotic microorganisms to extract and fix nitrogen from the air , for example legumes such as peas, beans, lupins with "nodule bacteria" ( Rhizobium leguminosarum ) living in the roots . Ammonia is formed from amino groups in the organic substance by hydrolysis . This reacts with water to form OH - and NH 4 + . The ammonium ion is oxidized to nitrite by the soil bacteria Nitrosomonas and further by Nitrobacter to nitrate .

With organic (“natural”) fertilizers, the nitrogen is gradually released through microbial degradation - depending on the soil temperature, humidity and grain size of the raw material. Mineral fertilizers, on the other hand, work faster because they can be absorbed directly by the plant roots as water-soluble compounds.

Examples of nitrogen fertilizers

See also

Individual evidence

  1. ↑ Jörg Albrecht: 100 years of the Haber-Bosch process: bread and wars from the air. In: Frankfurter Allgemeine Zeitung . FAZ.net, October 14, 2008, accessed on November 27, 2019 .
  2. ↑ Susanne Kurz, Thilo Heinken, Thomas Fartmann: Nitrogen enrichment in host plants increases the mortality of common Lepidoptera species . In: Oecologia . tape 188 , 2018, p. 1227-1237 , doi : 10.1007 / s00442-018-4266-4 .
  3. ↑ Rockström, J. et al., A safe operating space for humanity . In: Nature , 461 (7263), (2009), 472-475, doi : 10.1038 / 461472a .
  4. ↑ Tallaksen et al., Nitrogen fertilizers manufactured using wind power: greenhouse gas and energy balance of community-scale ammonia production . In: Journal of Cleaner Production 107, (2015), 626–635, doi : 10.1016 / j.jclepro.2015.05.130 .