Phosphate Availability

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•  Phosphorus can be added to the phosphorus cycle by application of fertiliser or removed by the harvesting of

    agricultural crops

Phosphates can be removed from the lithosphere via mining and converted into phosphate-based fertilisers

  • This allows phosphates that would otherwise remain unaccessible in buried rocks to become available for plant use

The fertilisers are then transported to crops in order to increase their productivity by increasing plant access to phosphate

  • When the crops are harvested, the phosphates that comprise part of the plant’s biomass are lost from the phosphorus cycle

While the application of fertiliser adds phosphorus at one site, it causes the depletion of phosphorus reserves at another site

  • The continued production of phosphate-based fertilisers is depleting global phosphorus reserves at a rapid rate

The Role of Fertlisers in the Phosphorus Cycle


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•  Availability of phosphate may become limiting to agriculture in the future

The demand for fertiliser in agriculture is very high, however the rate of turnover in the phosphorus cycle is very low

  • This means that phosphates are being removed from the lithosphere at a much faster rate than they are being replenished
  • Consequently, phosphate minerals are classified as a non-renewable resource

Current estimates predict that the availability of phosphates may become severely restricted within 50 – 100 years

  • This would greatly limit the crop yield per unit of farmland due to the reduced use of phosphate-based fertilisers
  • There are currently no synthetic ways of creating phosphate-based fertiliser (although this could change in the future) 

Phosphate Availability and Use

                            Data:         Phosphate Availability             Phosphate Use