nutrient cycle

• importance of nitrogen in nitrogen cycle:

  • 78% nitrogen in air but plants and animals cannot obtain nitrogen through gas exchange = nitrogen gas contains a triple bond which is hard to break
  • microorganism needed to convert nitrogen gas into nitrogen containing substances
• The nitrogen cycle:

  1. Saprophytic digestion = proteins into amino acids
  2. Ammonification = amino acid into ammonia
  3. Nitrification = ammonia into nitrites and nitrates
  4. Nitrogen- fixing = atmospheric nitrogen into ammonia
  5. Denitrification = nitrates into nitrogen in the atmosphere
• mycorrhizae is the symbiotic / mutualistic relationship between fungi found around certain plant roots: beneficial

  • fungi increases the surface area for water and mineral absorption
  • fungi acts as a sponge holding water and minerals around the roots
  • helps plants to resist droughts by helping it take up more inorganic ions more readily
• The phosphorus cycle describes the movement of phosphate through ecosystems, linking living and non-living components. This cycle incorporates several processes that facilitate the recycling of phosphorus, a resource that is often limited in availability.
• phosphorous is found in rocks and dissolved in the oceans in the form of phosphate ions (PO43-)

  • Brought to the surface by the geological uplifting of rocks.
  • The weathering and erosion of these rocks helps phosphate ions to become dissolved and so available for absorption by plants which incorporate them into their biomass.
  • Phosphate ions dissolved in water in the soil can be assimilated (absorbed and used to make more complex molecules by plants / producers).

  Phosphorus cycle lacks a gaseous phase altogether.
• PHOSPHORUS CYCLE:

  1. weathering / erosion  = Phosphate ions in rocks are released into the soil or into sea/rivers
  2. Absorption by producers = Plants, with the help of mutualistic mycorrhizal fungi in their roots, [increase the rate of assimilation] and algae absorb phosphate ions from the soil or water
  3. Consumption = Phosphates are transferred through food chains when organisms consume other organisms
  4. Excretion and death = Excess phosphate ions exit organisms when they die and via their waste products
  5. Decomposition = saprobionts, like bacteria and fungi, break down dead material, releasing phosphate ions for reabsorption by producers by producers
  6. Sedimentation and deposition - Phosphates in water sources, waste, or dead organic matter accumulate and reform sedimentary rocks.
• NITRATES AND PHOSPHATES ARE LOST FROM THE SYSTEM WHEN:

  Crops are harvested = Crops take in minerals from the soil as they grow and use them to build their own tissues.

  • When crops are harvested, they're removed from the field rather than dying and decomposing there
  • This means the mineral ions (phosphates/nitrates) are not returned to the soil by saprobionts.

  
  

  Animals are moved:

  • They eat grass and other plants which takes in their nutrients so removing them elsewhere or for slaughter, the nutrients are not replaced through remains or waste products. 
• WHAT FERTILISERS DO

  Necessary to replenish these mineral ions because, otherwise, their reduced concentrations will become the main limiting factor to plant growth = Resulting in reduced productivity

  • To offset this loss of mineral ions, fertilisers need to be added to the soil.
  • Fertilisers improve the efficiency of energy transfer (more energy can be used for growth) 
  • Increase productivity