Nutrient Cycles (Fertilisers) + Leaching + Eutrophication

• Denitrifying


  Extracellular digestion: external digestion from bacteria
• Nitrogen Cycle


  1. Nitrogen fixation

  2. Ammonification

  3. Nitrification

  4. Denitrification
• Saprobiotic nutrition


  Obtaining nutrients from dead matter via extracellular digestion
• Mycorrhizae


  • Symbiotic relationship between plants and fungi/bacteria
  • Plant provides carbs, fungi/bacteria provide nitrogen
• Nitrogen fixation


  N2 converted to nitrogen containing compounds by nitrogen-fixing bacteria
• Nitrogen fixation


  N2 + 3H2 -> NH3
• Ammonification


  Nitrogen compounds in waste and dead organisms converted into ammonia by saprobiants
• Nitrification


  Ammonia converted into nitrites then nitrates by aerobic nitrifying bacteria
• Denitrification


  Waterlogged soil with low oxygen causes denitrifying bacteria to convert nitrates back to gaseous N2
• Nitrates also used in production of proteins/amino acids/RNA/DNA/NAD/NADH in organisms/animals
• Denitrification reduces nitrate availability, so plants/crops don't thrive
• Phosphorus Cycle


  1. Phosphate ions being translocated and transformed in soil, water, living/dead organic material

  2. Phosphate ions in rocks released into soil by weathering

  3. Phosphate ions taken into plants through roots with help from mycorrhizae

  4. Phosphate ions transferred through food chains - animals eat plants

  5. Phosphate ions lost from animals in waste (faeces + urine)

  6. Dead/decaying matter broken down by saprobionts - releases phosphate ions

  7. Weathering of rocks releases phosphate ions into seas

  8. Waste of sea birds - guano contains high proportion of phosphate ions

  9. Guano returns significant amounts of phosphate ions into soil
• Guano


  Waste product that is excreted by seabirds (natural fertiliser)
• Mycorrhizae


  Symbiotic relationship between plant roots and fungi that increases the rate of phosphate being assimilated
• Types of fertilisers


  • Natural
  • Artificial
• Natural fertilisers


  • Contain organic matter (e.g. powder, pellets)
  • Nutrients released over a long period of time
  • Easy to use, easy to know how much is being applied and effects on crop yield
  • Lower concentration of nutrients, smaller amounts needed
• Artificial fertilisers


  • Inorganic compounds
  • High concentration of nutrients, large amounts needed
  • Easy to apply
• Use of fertilisers


  • Increases rate of photosynthesis
  • Improves crop productivity
  • Improves soil structure
  • Reduces soil erosion
  • Increases water holding in soil
• Leaching of nitrogen-containing fertilisers


  • Reduces species diversity - nitrogen rich soil favours growth of grasses that outcompete slower growing plant species
  • Leads to pollution of watercourses
  • Causes eutrophication
• Natural


  Natural
• Artificial


  Artificial
• Leaching itself is not a damaging process but the knock-on effects of this (i.e. eutrophication) can be very damaging to aquatic ecosystems
• Lightning strikes can convert some atmospheric nitrogen gas (N2) into reactive nitrogen species (nitric oxide [NO], nitrous acid [HNO3], and nitrate ion [NO3-]).
• Nitrogen is an essential nutrient that plants need to grow.
• The nitrogen cycle involves the conversion of atmospheric nitrogen into forms usable by living organisms, such as ammonia or organic compounds like proteins.
• This natural source of nitrogen is known as 'biological fixation' or 'lightning fixation'.
• LEACHING

  Process of mineral ions being dissolved by rainwater into waterways from farmland
• EUTROPHICATION

  Process of excess mineral ions (nitrates + phosphate ions) from fertilisers causing rapid growth of algae, leading to algal bloom and depletion of dissolved oxygen in water
• Eutrophication

  1. Excess mineral ions (nitrates + phosphate ions) from fertilisers don't get taken up by plants

  2. Rapid growth of algae = algal bloom

  3. Algal bloom blocks sunlight from reaching aquatic plants/organisms at lower depths

  4. Algae start to die due to competition for nutrients

  5. Decomposing bacteria increase, decreasing dissolved oxygen supply

  6. Aquatic organisms unable to survive from lack of oxygen and nutrients
• Leaching of artificial fertilisers is the main cause of eutrophication
• Other causes of eutrophication

  • Organic matter/Manures
  • Animal slurry
  • Human sewage
  • Ploughing and grassland natural leaching
• High nitrate ion concentration in drinking water can have harmful effects on humans, especially babies
• Leaching and eutrophication releases more toxins and nitrates which turn the water putrid