nitrogen cycle

noun

1. the continuous sequence of events by which atmospheric nitrogen and nitrogenous compounds in the soil are converted, as by nitrification and nitrogen fixation, into substances that can be utilized by green plants, the substances returning to the air and soil as a result of the decay of the plants and denitrification.

nitrogen cycle

noun

1. the natural circulation of nitrogen by living organisms. Nitrates in the soil, derived from dead organic matter by bacterial action, are absorbed and synthesized into complex organic compounds by plants and reduced to nitrates again when the plants and the animals feeding on them die and decay See nitrification nitrogen fixation

nitrogen cycle

1. The continuous process by which nitrogen is exchanged between organisms and the environment. Nitrogen is an essential nutrient, needed to make amino acids and other important organic compounds, but most organisms cannot use free nitrogen, which is abundant as a gas in the atmosphere. Gaseous nitrogen is broken apart and fixed (converted to stable, biologically assimilable inorganic compounds) in the process of nitrogen fixation . Some atmospheric nitrogen is fixed naturally during lightning strikes and some by industrial processes. Cyanobacteria and certain other species of bacteria, especially those living as symbionts in the roots of legumes, fix atmospheric nitrogen biologically in ammonium ions. Ammonia and ammonium ions are also produced by the ongoing decay of organic materials. Ammonia can be absorbed directly by plant cells, and certain bacteria living in soil and water convert ammonia and ammonium ions into nitrites and nitrates in the process known as nitrification . The nitrates are easily absorbed by plant roots. In this way, nitrogen is passed into the food chain and ultimately returned to the soil, water, and atmosphere by the metabolism and decay of plants and animals.

Word History and Origins

Origin of nitrogen cycle¹

First recorded in 1905–10

Example Sentences

"We wanted to know more about the role these different sulfur bacteria play in the nitrogen cycle."

From Science Daily

Knowing more about the plant and soil nitrogen cycle can affect emissions of N2O, a gas that accounts for 6% of all greenhouse gas emissions in the United States.

From Science Daily

"There is a major blind spot in the nitrogen cycle," Margenot said.

From Science Daily

And it could directly leak fugitive ammonia emissions into the environment, also forming air pollutants, impacting water quality, and stressing ecosystems by disturbing the global nitrogen cycle.

From Science Daily

"If you can understand the genetic mechanisms that control nitrate uptake and signaling, as well as how plants can better use nitrate, it's advantageous for agriculture, soil, water, fertilizer application and the entire nitrogen cycle."

From Science Daily