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Science

Fertilisers and crop yields

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Fertilisers contain minerals such as nitrogen, potassium and phosphorus, which help plants to grow. Fertilisers increase crop yields but cause the problem of eutrophicationeutrophication: 'hyper-nutrition' resulting from fertiliser pollution of aquatic ecosystems. Results in oxygen depletion and reduced ability to support life when they're washed into rivers and lakes by rainwater. Most chemical fertilisers are made by the reaction of an acid with an alkali.

Fertilisers

Fertilisers make crops grow faster and bigger so that crop yields are increased. They are water-soluble minerals. They must be able to dissolve in water so that plants can absorb them through their roots.

Fertilisers provide plants with the essential chemical elements needed for growth particularly nitrogen, phosphorus and potassium.

A crop field

Ammonia is used in fertilisers for crops

The name or formula of a compound often suggests which elements are provided by a particular fertiliser. The table shows some examples.

Examples of fertilisers, their formula and the essential elements

fertiliserformulaessential elements
ammonium nitrateNH4NO3nitrogen
ammonium sulfate(NH4)2SO4nitrogen
ammonium phosphate(NH4)3PO4nitrogen and phosphorus
potassium nitrateKNO3potassium and nitrogen
urea(NH2)2COnitrogen

Fertiliser problems

The world population is increasing all the time, so more food has to be produced. Without fertilisers the yields of crops would be reduced. However, if too much fertiliser is used it can pollute water supplies. It may also lead to eutrophication, a situation where there is not enough oxygen dissolved in the water for aquatic organisms to survive.

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