1.5 The Nitrogen Cycle

Nitrogen Fixation

- Process of N2 gas being converted into biologically available NH3 (ammonia) or NO3 (nitrate)
- Three types: Abiotic, Bacterial, Synthetic

Bacterial Fixation

- Certain bacteria that live in the soil, or in a symbiotic relationship with plant root nodules convert N2 into NH3 (ammonia)

Synthetic Fixation

- Humans combust FFs to convert N2 gas into NO3
- NO3 added to fertilizers and used in agriculture

Abiotic Fixation

- Lightning strikes can turn N2 into the biologically available NO3 and NH3

Assimilation

- Plants and animals take N in and incorporate it into their body
- Plants: Roots take in NO3 of NH3 from the soil
- Animals: Eat plants or other animals

Ammonification

- Soil bacteria, microbes, and decomposers convert waste and dead biomass back into NH3 and return it to the soil

Nitrification

- The conversion of NH4 into NO2 (nitrite) and NO3 (nitrate) by soil bacteria

Denitrification

- The conversion of soil N into nitrous oxide (N2O) gas which returns to the atmosphere

Ammonia Volatilization

- Excess fertilizer use can lead to NH3 gas entering the atmosphere
- Creates acid rain + respirator illness in humans and animals

Nitrous Oxide (N2O)

- Greenhouse gas that warms up earth's climate
- Produced by denitrification of nitrate in agricultural soils

Eutrophication & Leaching

- Synthetic fertilizer use leads to NO3 leaching, or being carried out of soil by water