Saturday, 11 February 2012

5.3 Fertilisers

Understand the use of fertiliser to increase crop yield.

Farmers normally add fertilisers (mostly in the form of nitrates or phosphates) to the soil in order to help promote the growth of crops and increase yield. These nutrients are taken up by the root structure and then moved in the transpiration stream up to the leaves for the construction.

Nitrates will go up to form proteins which is then used by the plants to generate/repair cells.
Phosphate is involved in the DNA of plants and the membranes of the plant.

The fertilisers can be divided into two groups:


  • Made from animal manures (waste) on farms and often goes through the process of decomposition and fermentation and forms a slurry compound
  • This is applied to the fields to provide Nirates and Phosphates to promote growth

Inorganic (Artificial):

  • These take the form of chemicals (synthetically produced), well known ones are potassium nitrate and ammonium nitrate which can be bought by the farmers and applied to the fields
  • These will release the nitrates which will promote growth of the crops.

Consequences of using fertilisers:
  • Fertilisers may run-off due to excess rain and reach water sources of causes eutrophication. The fertilizers enrich the nutrient content in water sources which causes algal blooms where the algaes grow fast and multiply. When algae die they are broken down by decomposers, the process of decomposition uses up oxygen in the water sources and causes massive die-off of fishes.
  • Fertilisers may be hazardous to human health: for example, organic fertilisers might leach through to water sources and cause diseases such as E.Coli which is commonly found in cow manures. Inorganic fertilizers may also leach down to underground water sources and cause cancer and is toxic to humans.
  • Fertilisers are normally used in intensive farming techniques (when a farmer is trying to obtain as much as possible from each hectare of land) which may deplete the original soil nutrients.

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