describe the occurrence of nitrogen cycle
Answers
The nitrogen cycle is the biogeochemical cycle by which nitrogen is converted into multiple chemical forms as it circulates among atmosphere, terrestrial, and marine ecosystems. The conversion of nitrogen can be carried out through both biological and physical processes. Important processes in the nitrogen cycle include fixation, ammonification, nitrification, and denitrification. The majority of Earth's atmosphere (78%) is atmosphere nitrogen,[1] making it the largest source of nitrogen. However, atmospheric nitrogen has limited availability for biological use, leading to a scarcity of usable nitrogen in many types of ecosystems.
The nitrogen cycle is of particular interest to ecologists because nitrogen availability can affect the rate of key ecosystem processes, including primary production and decomposition. Human activities such as fossil fuel combustion, use of artificial nitrogen fertilizers, and release of nitrogen in wastewater have dramatically altered the global nitrogen cycle.
The atmosphere contains mainly nitrogen. in fact, the percentage of nitrogen in the air is 78%.
1) Atmospheric nitrogen is converted into nitrates in the soil by nitrogen fixing bacteria present in the root nodules of leguminous plants.
2)Nitrogen fixing bacteria present freely in the soil convert atmospheric nitrogen into ammonia in the soil.
3) Nitrates in the soil are assimilated (absorbed or taken up) by plants.
4) Plants are eaten by animals.
5) When plants and animals die or excrete, the nitrates and ammonia go back into the soil.
6) Denitrifying bacteria converts nitrates in the soil back into atmospheric nitrogen and thus the cycle continues.
7)NOTE- atmospheric nitrogen can also be converted into nitrates in the soil by lightening storms. lightening creates so much energy in the atmosphere that the atmospheric nitrogen reacts and enters the soil as nitrates.