Knowra Nitrogen cycle Nitrogen cycle The movement and transformation of nitrogen among the atmosphere, soil, water, and living organisms through biological, chemical, and geological processes.
Nitrification : The microbial oxidation of ammonia or ammonium to nitrite and then nitrate. This soil process converts reduced nitrogen into nitrate that plants can absorb or water can carry away.
Nitrogen : The chemical element with atomic number 7, abundant in the atmosphere and essential to life. Its changing chemical forms, rather than the element itself, drive the cycle’s transfers.
Haber–Bosch process : An industrial method for synthesizing ammonia from nitrogen and hydrogen under high pressure and temperature. It supplies fertilizer nitrogen at a scale that has substantially altered the global cycle.
Nitrogen deposition : The transfer of reactive nitrogen from the atmosphere to Earth’s surface through wet or dry processes. Emissions move cycle nitrogen into ecosystems far from its original source.
Global nitrogen cycle : The planetary-scale movement of nitrogen among the atmosphere, land, freshwater, and oceans. Global budgets reveal how human inputs have shifted nitrogen flows across Earth’s systems.
Assimilation (biology) : The incorporation of inorganic nutrients into organic molecules by organisms. Plants and microbes assimilate ammonium or nitrate into the organic nitrogen that moves through food webs.
Nitrogen fixation : The conversion of atmospheric nitrogen gas into chemically usable forms such as ammonia. Understanding fixation clarifies why organisms cannot directly use the atmosphere’s nitrogen gas.
Synthetic fertilizer : Manufactured plant nutrient material containing chemically available nitrogen, phosphorus, or potassium. Nitrogen fertilizer adds reactive nitrogen to fields beyond what biological fixation alone supplies.
Acid rain : Precipitation made unusually acidic by atmospheric pollutants, including nitrogen oxides and sulfur compounds. Nitrogen oxides formed during combustion can return to land and water as acidic deposition.
Nitrogen budget : An accounting of nitrogen inputs, outputs, and storage within a defined system and period. Uncertain measurements of sources and sinks limit precise estimates of cycle change.
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