As I understand the food supply chain, organic compounds have to be created from a unlimited source (air, water...).

For instance, I figure that plants transform CO2 from air to organic carbon compounds, mainly carbohydrates, which are then the main source for most other life forms.

But I never heard about a plant turning atmospheric N2 to nitrogen compounds.

Where nitrogen compounds come from, and from which source ?


There are nitrogen fixing bacteria who turn N2 into NH3. Some are free-living in soil, others live symbiotically with plants.


  • 1
    $\begingroup$ Also some is fixed by inorganic processes, e.g. lightning converting nitrogen into various oxides. $\endgroup$ – jamesqf Jul 2 '18 at 18:51

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