nitrogen cycle defined in 1951 yearnitrogen cycle - nitrogen cycle;
nitrogen cycle - Circulation of nitrogen atoms brought about mainly by living things. In outline, inorganic nitrogen compounds (chiefly nitrates), are absorbed from soil or water and built up into organic compounds by autotrophic plants. These die or decay or are eaten by animals and the nitrogen, still as organic compounds, returns to soil or water in their excreta or by their death and decay. Bacteria then convert them to inorganic nitrogen compounds. Some nitrogen is lost to the atmosphere as gas, and some is extracted from the atmosphere by nitrogen-fixing bacteria and blue-green algae.
near nitrogen cycle in Knolik
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