nitrogen cycle


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ni·tro·gen cy·cle

the series of events in which the nitrogen of the atmosphere is fixed, thus made available for plant and animal life, and is then returned to the atmosphere: nitrifying bacteria convert N2 and O2 to NO2- and NO3-, the latter being absorbed by plants and converted to protein; if plants decay, the nitrogen is in part given up to the atmosphere and the remainder is converted by microorganisms to ammonia, nitrites, and nitrates; if the plants are eaten, the animals' excreta or bacterial decay return the nitrogen to the soil and air.

nitrogen cycle

n.
The circulation of nitrogen in nature, consisting of a cycle of chemical reactions in which nitrogen from the atmosphere is fixed in compounds in soil or water, assimilated by plants and animals, released to the soil and water through decomposition, and returned to the atmosphere through denitrification.

ni·tro·gen cy·cle

(nī'trŏ-jĕn sī'kĕl)
The series of events in which the nitrogen of the atmosphere is fixed, thus made available for plant and animal life, and is then returned to the atmosphere: nitrifying bacteria convert N2 and O2 to NO2- and NO3-, the latter being absorbed by plants and converted to protein; if plants decay, the nitrogen is in part given up to the atmosphere and the remainder is converted by microorganisms to ammonia, nitrites, and nitrates; if the plants are eaten, the animals' excreta or bacterial decay return the nitrogen to the soil and air.
Nitrogen cycleclick for a larger image
Fig. 229 Nitrogen cycle .

nitrogen cycle

the circulation of nitrogen in the environment as a result of the activity of living organisms. 80% of the atmosphere is made up of nitrogen and this is maintained by the balancing action of the cycle.
References in periodicals archive ?
For more information on the nitrogen cycle, especially N fixation, see: <http://helios.bto.ed.ac.uk/bto/microbes/nitrogen.htm>.
Human interference on the nitrogen cycle in BLPB is related to a growing economy and its population--approximately 60 million inhabitants--that demands food, raw material and energy.
"The nitrogen cycle is a terrific example of that."
The nitrogen cycle goes like this: Alfalfa is planted as a forage for animals.
"We were really shocked; everything we've ever thought about the nitrogen cycle and all of the textbook theories have been turned on their heads by these data," said Professor Benjamin Houlton, a biogeochemist and one of the study's co-authors.
In doing so, we are altering the global nitrogen cycle, causing possible grave impacts on biodiversity, global warming, water quality, human health, and even the rate of population growth in developing nations.
For my own purposes, the chapters by Hsiao and Jackson (on water stress) and Hungate (on feed-backs through the nitrogen cycle) are particularly good resources.
Or perhaps tall whitetop somehow disrupts the nitrogen cycle in the soil, making it impossible for other plants to flourish, says Robert R.
The fact that soil emits HONO is not just locally, but also globally significant for air quality and the nitrogen cycle.