Nitrogen and Fertilisers

Nitrogen and Fertilisers

Nitrogen in the Air

  • Nitrogen makes up about 78% of the Earth’s atmosphere.
  • It is an inert gas, meaning it does not easily react with other elements.
  • Nitrogen is essential for plant growth as it’s a key component of proteins, amino acids, and chlorophyll.
  • The nitrogen found in the air, however, is difficult for plants to absorb directly.

Nitrogen Cycle

  • The process of converting nitrogen gas into a form that can be used by plants is called the nitrogen cycle.
  • This involves the action of nitrogen-fixing bacteria which convert nitrogen gas into nitrates which plants can absorb.
  • Animals then eat the plants and the nitrogen compounds move up the food chain.
  • Decomposers break down the bodies of dead animals and plants, returning nitrates to the soil.

Fertilisers

  • Fertilisers are substances added to soil to supply essential nutrients to plants.
  • Fertilisers often contain nitrates because they are easily absorbed by plant roots.
  • By using nitrogen-based fertilisers, farmers can improve crop yield and the overall quality of the crop.

Manufacturing Fertilisers

  • One method of producing nitrogen-based fertilisers is the Haber-Bosch process.
  • In this process, nitrogen gas and hydrogen gas combine to produce ammonia. The ammonia can then be treated with nitric acid to produce ammonium nitrate.
  • The amount of ammonia produced is optimised by carefully controlling temperature, pressure, and using iron-based catalysts.

Environmental Impact of Fertilisers

  • Overuse of fertilisers can lead to eutrophication, a process that causes algal blooms and depletion of oxygen in aquatic environments.
  • Excessive fertiliser can also contaminate drinking water with nitrates, which can be harmful or even deadly if ingested in large amounts.
  • Therefore, it is important to manage the use of fertilisers effectively to minimise their environmental impact.

Alternative and Sustainable Methods

  • Crop rotation with legumes, which house nitrogen-fixing bacteria in their roots, can help replenish soil nitrogen levels naturally.
  • Composting organic waste material can also provide plants with necessary nutrients, reducing dependency on synthetic fertilisers.