Essential idea: Soil cycles are subject to disruption.

Intensive agriculture relies heavily on the use of artificial fertilisers to maintain high crop yields. The manufacture and the application of fertilisers is a major disruption to nutrient cycles. One consequences of this is the unbalancing of natural ecosystems around agricultural areas.

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Understandings, Applications and Skills

C.6.U1	Nitrogen-fixing bacteria convert atmospheric nitrogen to ammonia.
C.6.U2	Rhizobium associates with roots in a mutualistic relationship.
C.6.U3	In the absence of oxygen denitrifying bacteria reduce nitrate in the soil.
C.6.U4	Phosphorus can be added to the phosphorus cycle by application of fertilizer or removed by the harvesting of agricultural crops.
C.6.U5	The rate of turnover in the phosphorus cycle is much lower than the nitrogen cycle.
C.6.U6	Availability of phosphate may become limiting to agriculture in the future.
C.6.U7	Leaching of mineral nutrients from agricultural land into rivers causes eutrophication and leads to increased biochemical oxygen demand.
C.6.A1	The impact of waterlogging on the nitrogen cycle.
C.6.A2	Insectivorous plants as an adaptation for low nitrogen availability in waterlogged soils.
C.6.S1	Drawing and labelling a diagram of the nitrogen cycle.
C.6.S2	Assess the nutrient content of a soil sample.

[Text in square brackets indicates guidance notes]

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Starters

Hank from Crash Course introduces the Nitrogen and Phosphorous cycles

Mohamed Hijri in his TED.com talk offers a simple solution to the coming phosphorus crisis.

Presentation and Notes

The presentation is designed to help your understanding. The notes outline is intended to be used as a framework for the development of student notes to aid revision.

Vocabulary

Correct use of terminology is a key skill in Biology. It is essential to use key terms correctly when communicating your understanding, particularly in assessments. Use the quizlet flashcards or other tools such as learn, scatter, space race, speller and test to help you master the vocabulary.

Quick quiz

Use the BioK Quick Quiz on C.6 The nitrogen and phosphorous cycle (as directed) to check your understanding of the topic

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Weblinks

_Nitrogen Cycle
Root nodule formation by McGraw and Hill
What is the Nitrogen cycle? by Braingenie

Phosphorous Cycle
The Phosphorous Cycle by Sunamas Inc.

Eutrophication
Eutrophication by Absorb Learning
Eutrophication by Rutgers University Cool Classroom design team

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Nature of science

Assessing risks and benefits of scientific research—agricultural practices can disrupt the phosphorus cycle. (4.8)