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 ?
Galloway JN, Leach AM, Bleeker A, Erisman JW (2013) A chronology of human understanding of the nitrogen cycle.
Keeney DR, Hatfield JL (2008) The nitrogen cycle, historical perspective, and current and potential future concerns.
A fuller picture of how humans interacted with the nitrogen cycle began to emerge.
Not surprisingly, the nitrogen cycle has received a good portion of that scrutiny, with researchers analyzing flows of nitrogen at a variety of different scales, from the level of streams and forests to oceans and continents (Mosier et al.
The story of N: A social history of the nitrogen cycle and the challenge of sustainability.
Considering the importance of the nitrogen cycle to human wellbeing and the fact that the most rapid changes in ecosystems are taking place in developing countries (MEA, 2005), this paper will assess the anthropogenic nitrogen cycle in the Brazilian La Plata Basin (BLPB)--which is one of the most important watersheds in Brazil because of its large agricultural area and growing population in urban centres, such as the city of Sao Paulo.
Measuring anthropogenic influence on nitrogen cycle in BLPB
et al 2003 Human health effects of a changing global nitrogen cycle The Ecological Society of America 1: 240-246.
2007 Microbiology/ Biochemistry of the Nitrogen Cycle Innovative Process Applications Moving forward wastewater biosolids sustainability: technical, managerial, and public synergy GMSC, New Brunswick, pp 277-285.
Indeed, it has been predicted that humans will double the turnover rates of the terrestrial nitrogen cycle.
The manifold consequences of anthropogenic influences over the planetary nitrogen cycle have been investigated by many regional and international research groups.