Nitrogen Cycle

• main processes of nitrogen cycle


  Ionisation, fixation, food chains, nitrification, denitrification, leaching, root absorption, ammonification
• Ionisation


  energy being provided for atmospheric nitrogen and oxygen to react and produce oxides of nitrogen

  (energy from lightning and meteor trails)
• Fixation


  micro-organisms chemically reducing nitrogen to ammonia.
• where do the micro-organisms that reduce nitrogen to ammonia live?


  either free-living in the soil or may live symbolically in the root nodules of legumes
• food chains


  nitrogen passed between organisms as amino acids and proteins in food
• nitrificaiton


  the oxidation of ammonium ions to nitrites, then to nitrates by nitrifying bacteria in the soil
• Denitrification


  chemical reduction of nitrates in soil to nitrogen and nitrogen oxide gases

  reduced soil fertility and occurs under anaerobic conditions
• Leaching


  highly solubility of nitrates means they are easily leached out soils into water
• Assimilation/ root absorption


  plant absorbs nitrogen as soluble ions, mainly as nitrates but also as ammonium ions
• Ammonification


  the amino groups in proteins are released ammonium ions by bacteria, fungi and detritivores as they decompose dead organic matter
• Volatilisation


  conversion of liquid chemical into vapour, which escapes into the atmosphere

  -nitrates out of soil or from fertiliser
• human impacts on the nitrogen cycle


  - haber process

  - agriculture

  - pollution
• haber process


  an industrial process for producing ammonia from nitrogen and hydrogen by combining them under high pressure in the present of an iron catalyst
• Agriculture


  -Use of nitrate fertilisers may increase the problems caused by leaching forexample eutrophication

  -Drainage of field makes the soil more aerobic increases the number of aerobic nitrifying bacteria and reduces the number of anaerobic denitrifying bacteria

  -Soil disturbance increases rate of decomposition which releases more nitrogen oxides into the atmosphere

  -Leguminous plants such as peas, beans and clover may be grown to increase the levels of nitrogen compounds in the soil
• Pollution


  -oxides of nitrogen are released into the atmosphere by combustion processes and may subsequently increase the quantity of nitrates washed into the soil
• sustainable management odds nitrogen cycle


  -control of combustion processes

  -control of NOX release

  - management of

  biological wastes

  - eutrophication

  - organic fertilisers

  - management of soil processes
• Control of combustion processes

  Reduction in the use of fossil fuels would reduce NOx release adopting principles of the circular economy->low temp manufacturing process
• Control of NOx releases


  Reduced by post combustion processes -> Catalytic converters and urea sprays
• Organic fertiliser


  Was such as manure, sewage and food production waste may be used in organic fertilisers to increase nutrients and humus levels
• Management of soil processes

  change in farming practices:

  -crop rotation

  -Cultivation of legume crops

  -Minimal use of pesticides

  -Control nitrate leaching

  -Not using fertilisers during rain season

  -Low solubility fertilisers

  -Uncultivated buffer strips
• nitrogen cycle steps


  nitrogen fixation (nitrogen-> ammonia), assimilation (ammonia -> plants), ammonification (decomposing), nitrification (ammonia -> nitrites -> nitrates) by nitrifying bacteria, denitrification (nitrates -> nitrogen in atmosphere)