1.5 Nitrogen Cycle

What is the nitrogen cycle?

The movement of nitrogen containing molecules between sources and sinks/reservoirs

What are nitrogen sources?

things that release nitrogen into the atmosphere

What are nitrogen sinks

things that take in nitrogen from the atmosphere in big amounts

what is significant about Nitrogen reservoirs compared to carbon reservoirs

reservoirs hold N for relatively SHORT periods of time compared to Carbon reservoirs

• N reservoirs include:

  • plants, soil, atmos

Why is N important to plants and animals?

It is an important nutrient as it is a building block for DNA and amino acids

Nitrogen fixation

process of N₂ gas (unusable to plants and animals) being converted into biologically available NH₃ (ammonia) and NO₃^- (nitrate)

How can N fixation happen naturally?

bacterial fixation, lightning

Bacterial fixation

when certain bacteria that live in the soil and have a symbiotic relationship with plant roots to convert N₂ into NH₃

• bacteria known as rhizobacteria live in root nodules of legumes and fix N for plants in exchange for amino acids from the plant

how does N fixation occur synthetically?

humans combus FFs into N₂ gas into NO₃^- to help create synthetic fertilizers

Assimiliation

plants and animals take N in and incorporate it into their body

• plant roots take in NO₃^-/NH₃ from soil and then the animals eat the plant or other animals who have already assimilated with N

Ammonification

where soil bacteria, microbes, and decomposers convert waste/dead biomass into NH₃ and return it to the soil

Nitrification

where NH₄ gets converted into NO₂^- (nitrite) and then into NO₃ (nitrate) by soil bacteria

Denitrification

conversion of soil N (NO₃) into nitrous oxide (N₂O) and returns it to the atmosphere

what is the significance of ammonifcation and assimilation

they are the reserve of each other. Assimilation is when N is absorbed and ammonification is when it is released back into the environment

How does excess N lead to climate change?

N₂O = greenhouse gas. more of it leads to a warmer earth’s climate

• N₂O is produced by the denitrification of nitrate in overwatered agricultural soils

Ammonia volatization

where excess fertilizer leads to more NH₃ gas entering the atmosphere

• NH₃ gas can later join with rain and make it acidic, causing respiratory problems

Leaching

where NO₃ is carried out of soil into bodies of water (due to use of synthetic fertilizers)

Eutrophication

the death of aquatic life due to an algae bloom, caused by excess N and P in the environment