C6  Nitrogen and Phosphorus Cycles

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Essential Idea:

Soil cycles are subject to disruption


  • Nitrogen-fixing bacteria convert atmospheric nitrogen to ammonia
  • Rhizobium associates with roots in a mutualistic relationship
  • In the absence of oxygen denitrifying bacteria reduce nitrate in the soil
  • Phosphorus can be added to the phosphorus cycle by application of fertilizer or removed by the harvesting of agricultural crops
  • The rate of turnover in the phosphorus cycle is much lower than the nitrogen cycle
  • Availability of phosphate may become limiting to agriculture in the future
  • Leaching of mineral nutrients from agricultural land into rivers causes eutrophication and leads to increased biochemical oxygen demand


  • The impact of waterlogging on the nitrogen cycle
  • Insectivorous plants as an adaptation for low nitrogen availability in waterlogged soils


  • Drawing and labelling a diagram of the nitrogen cycle
  • Assess the nutrient content of a soil sample