Some plants fix atmospheric nitrogen and transform it into nitrogen compounds that are suitable for organisms. Such plants include pulse, clovers, vetchs and alfalfa. Most of these plants live in a symbiosis with a specific bacteria, for example Rhizobium in the case of leguminous plants or Frankia in the case of alder. Also cyanobacteria in soil, in the Baltic Sea or in symbiosis with fungi forming lichens fix nitrogen, as do some specific soil bacteria even without a symbiont plant.
Nitrogen fixation is crucial for life. Nitrogen compounds are needed to form, for example, amino and nucleic acids (including DNA) and proteins.Agriculture benefits from using nitrogen fixing plants such as pulse or clover in order to increase the nitrogen concentration of the fields and thus fertility of the soil. This is usually done as part of crop-rotation. Nitrogen-fixing plants are left to the fields as green manure and less synthetic nitrogen is needed the following year. Nevertheless, most of the nitrogen in agricultural soils is synthetic.
- Updated (20.01.2015)