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.

nitrogen cycle

Etymology: Gk, nitron, soda, genein, to produce, kyklos, circle
the circulation of nitrogen through natural processes in either of two ways: from the soil to organisms that excrete nitrogen products back into the soil or by bacterial fixation of atmospheric nitrogen through other organisms that decay and release the element back into the atmosphere.

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 ?
Although this process is crucial for the nitrogen cycle, especially in tropical forests, very few estimates are available (Cleveland et al.
2006), this paper aims to evaluate the level of human interference on BLPB's nitrogen cycle due to biological nitrogen fixation (BNF) in cropland and pastures, use of fertiliser in agriculture and anthropogenic depositions (N[O.
1 N2O, which is emitted throughout the nitrogen cycle, has 298 times the global warming potential of carbon dioxide (CO2) over a one hundred year period.
Cabello P, Dolores Roldan M, Moreno-Vivian C (2004) Nitrate reduction and the nitrogen cycle in archaea.
Most of the manure nitrogen can be returned to the soil, thereby completing the nitrogen cycle.
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.
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.
The book is likely to be sought after in and by the libraries of agricultural universities, but is unlikely to become a standard on the shelves of research scientists working on trace gas emissions or the nitrogen cycle.
x]) than scientists expected, suggesting they had overemphasized the importance of the nitrogen cycle.