1.5 The Nitrogen Cycle

Nitrogen Cycle

Movement of nitrogen (N) molecules between sources and sinks, involving processes like nitrogen fixation, assimilation, ammonification, nitrification, and denitrification.

Nitrogen Fixation

Process of converting N2 gas into biologically available forms such as NH3 (ammonia) or NO3- (nitrate).

NH3

Ammonia, a colorless gas produced in the nitrogen cycle that is highly soluble in water.

Nitrification

Conversion of NH4 (ammonium) into NO2- (nitrite) and then NO3- (nitrate) by soil bacteria.

Denitrification

Process through which soil nitrate (NO3) is converted into nitrous oxide (N2O) gas, returning nitrogen to the atmosphere.

Sources of Nitrogen

Reservoirs that release nitrogen into the atmosphere, including plants, soil, and the atmosphere itself.

Sinks of Nitrogen

Reservoirs that absorb nitrogen from the atmosphere, primarily plants and soil.

NO3-

Nitrate, a form of nitrogen that plants assimilate for growth and is formed during nitrification.

Ammonification

Conversion of waste and dead biomass into ammonia (NH3) by soil bacteria and decomposers.

N2

Nitrogen gas, the most abundant form of nitrogen in the atmosphere, which is not directly usable by most organisms.

Human Impacts on Nitrogen Cycle

Excess fertilizer use leads to ammonia volatilization and nitrate leaching, contributing to climate change and eutrophication.

N2O

Nitrous oxide, a greenhouse gas produced by denitrification that contributes to climate change.