The Nitrogen Cycle

The Nitrogen Cycle

Understanding the Nitrogen Cycle

  • The Nitrogen Cycle refers to the continuous series of natural processes by which nitrogen, found in various forms and levels of reactivity, is circulated through the air, earth, and living organisms.
  • Nitrogen is an essential nutrient for life, as it’s a fundamental part of amino acids and nucleic acids, which are necessary for the creation of proteins and DNA.
  • Nitrogen in the atmosphere is generally unavailable for plant use, therefore, it needs to be converted into a usable form by certain processes.

Steps of the Nitrogen Cycle

  • Nitrogen Fixation is the conversion of atmospheric nitrogen into a more usable form by certain bacteria and lightning strikes. These bacteria often live in a symbiotic relationship with legumes where they convert nitrogen into ammonia.
  • Nitrification is another process conducted by soil-living bacteria and consists of two steps: conversion of ammonia into nitrite, and then nitrite into nitrate.
  • Assimilation is where plants absorb these nitrates, converting them into plant protein.
  • Ammonification occurs when organisms excrete waste and die. The organic nitrogen in these wastes and dead materials is converted into ammonia by decomposers.
  • Denitrification is the final step, where certain bacteria in the soil convert nitrates back into nitrogen gas, which then enters back into the atmosphere, completing the nitrogen cycle.

Importance of the Nitrogen Cycle

  • The nitrogen cycle is crucial as it’s required for the production of essential molecules such as DNA and amino acids in living organisms.
  • Through this cycle, nitrogen is made available to plants, which form the basis of all food chains.
  • The nitrogen cycle also helps in maintaining the ecological balance in nature.

Impacts of Human Interference

  • Human activities such as the burning of fossil fuels, intensive farming and the use of nitrogen-rich fertilisers can significantly disrupt the nitrogen cycle, leading to a number of environmental problems.
  • These activities can cause an overabundance of nitrates in the environment, leading to water pollution and ‘eutrophication’ - excessive growth of plant and algal matter which chokes water bodies.
  • Substantial alterations to the nitrogen cycle can also contribute to global warming and the decline of certain ecosystems.