biogeochemical cycles - nitrogen cycle

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the nitrogen cycle

  • the nitrogen cycle is the biogeochemical cycle by which nitrogen is converted into multiple chemical forms as it circulates amoung the atmosphere, terrestrial + marine ecosystems
  • processes: fixation, ammonification, nitrification, denifriciation 
  • nitrogen is most abundant element in atmosphere 
  • nitrogen is abudant but need  to undergo processes before is becomes available, accessible + useable, need bacteria to convert it into nitrogen containing compounds 

what is the importance of nitrogen? 

  • nitrogen important for plant growth (structure), plant food processing + the creation of chlorophyll
  • without enough nitrogen in plant it cannot grow taller/produce enough food - this have impact on commercial crop growth 

how does nitrogen imapct the soil? 

  • without enough plant growth is negatively affected 
  • too much nitrogen plants produce excess biomass/organic matter e.g. leaves but not produce enough root strucuture 
  • very high levels of nitrogen absorbed from soils can poison farm animals that eat them 

whats the difference between nitrifying bacteria, denitrifying bacteria, nitrifying-fixing bacteria + decomposing the bacteria? 

  • nitrifying bacteria - converters of soil ammonia to nitrates, compound usable by plants 
  • denitrifying bacteria is the soil break down nitrates + return nitrogen to the air 
  • nitrogen fixing bacteria present in soil/in plant roots that change nitrogen gases from the atmosphere into solid nitrogen compounds that plants can use in the soil 
  • decomposers convert the nitrogen found in other organisms into ammonia + return it to the soil 

plants uptake nitrogen compound once nitrogen is converted into compounds like ammonium + nitrate, these be taken up from the soils by plants + then nitrogen be used to from macromolecules e.g. protiens 

Fixation: 

  • nitrogen in its gaseous from N2 cant be used by living things, it has be converted/fixed to a more useable form through a process called fixation, are three ways nitrogen be fixed to be more useful for living things: 
  • biologically - nitrogen gas diffuses into soil from the atmosphere + species of bateria convert this nitrogen into ammonium 
  • NH4+ derived from ammonia by combination with a hydrogen ion, a nitrogen compound taken up by plants from soils 
  • ions (NH4+) which be used by plants, legumes e.g. clover often grown by farmers as have nodules on their roots that contain nitrogen fixing bacteria 

Decomposition: 

  • plants take up nitrogen compounds through their roots, animals obtain these compounds when eat plants, when plants + animals die/when animals excrete wastes, the nitrogen compounds in the organic matter re-enter the soil where they are broken down by microorganisms - decomposers, this decomposition produces ammonia which then go through the nitrification process 

nitrification: 

  • nitrifying bacteria in the soil convert ammonia into nitrite (NO2-) + then into nitrate (NO3-) - process called nitrification 
  • compounds e.g. nitrate, nitrite, ammonia + ammonium can be taken up from the soils by palnts + then used in the formation of plant + animal proteins 

Denitrification: 

  • process where bacteria in soil breaks down nitrates into atmospheric nitrogen gas 
  • completes the nitorgen cycle by converting nitrate back into gaseous nitrogen, denitrifying bacteria are…

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