Crop Plants: Fertiliser (Edexcel IGCSE Biology (Modular)): Revision Note

Exam code: 4XBI1

Crop Plants: Fertilisers

  • Modern technology has increased food supply substantially

  • One of the key ways this has been achieved is with the use of fertilisers

  • Fertilisers increase the amount of key nutrients in the soil for crop plants, meaning that they can grow larger and are more healthy, which increases yields

Using fertilisers to increase crop yields

  • Plants require a range of mineral ions in order to grow well

  • As crop plants take up these mineral ions from the soil, the mineral ions need to be replaced if crops are grown repeatedly in the same field (i.e. year after year)

  • Fertilisers are used to replace these mineral ions

  • They can make crops grow faster and bigger so that yields are increased

  • Fertilisers can be in the form of organic fertiliser or chemical fertiliser

  • Organic fertilisers commonly used by farmers include farmyard manure and compost

  • Chemical fertilisers are often applied to the soil as dry granules or can be sprayed on in liquid form

  • Two mineral ions plants require for growth are magnesium ions and nitrate ions

Mineral ion

Function in plants

Sign of deficiency

Magnesium ions

needed for chlorophyll

yellowing of leaves

Nitrate ions

needed for amino acids (the building blocks of proteins)

weak growth and yellowing of the leaves

  • There are other mineral ions that plants require:

Mineral ion

Function in plants

Sign of deficiency

Phosphate ions

needed for ATP, DNA, RNA

poor root growth, dark green or purple-tinged leaves, stunted growth

Calcium ions

needed for cell walls and cell membranes

deformed new leaves, stunted growth

Potassium ions

needed for stomatal opening

yellowing at leaf edges

Examiner Tips and Tricks

The specification only requires you to know that magnesium ions are needed for chlorophyll and nitrate ions are needed for amino acids, so be sure to learn the functions of these two ions.

It's important to spell 'nitrate' correctly in the exam! Plants require nitrate ions, NOT nitrites or nitrogen.

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