Nitrogen Cycle

Nitrogen Fixation

Converts N2 gas into ammonium compounds which are then converted into nitrates in the soil. Free living bacteria in soil, bacteria in root nodules of leguminous plants. ( nitrogen-fixing bacteria )

Nitrogen can also be fixed by lightning or during producing of chemical fertilizers

Absorption if Nitrates

Plants take nitrate ions from soil through roots to build amino acids and proteins. Animals eat plants, so nitrogen moves through food chain.

Plants and animals die or produce waste.

Decomposers break down, this releases ammonia into the soil. Ammonification.

Nitrification

Plants can’t absorb ammonium ions, nitrifying bacteria converts ammonia into nitrites, then into nitrates which can then be taken up by plants.

Ammonia → nitrites → nitrates

Denitrifying Bacteria

Converts Nitrates back into N2 Gas, returning it into atmosphere. This happens in anaerobic conditions, e.g waterlogged or compacted soil.

This is reduced by ploughing soil to increase aeration.