5.4.4 Fertilisers

Types of Fertilisers

1. Natural (Organic) Fertilisers:

• Composed of dead and decaying organic matter, such as manure, compost, or sewage sludge.
• Release nutrients slowly as organic material decomposes.

2. Artificial (Inorganic) Fertilisers:

• Manufactured chemicals containing specific minerals, such as nitrates, phosphates, and potassium compounds (NPK fertilisers).
• Provide nutrients in a soluble form that plants can absorb immediately.

Advantages & Disadvantages of Fertilisers

Natural Fertilisers:

• Advantages:
  • Improves soil structure by increasing organic matter.
  • Encourages the activity of soil microorganisms.
  • Slow nutrient release reduces the risk of leaching.
• Disadvantages:
  • Nutrient content is variable and less concentrated.
  • May take time to decompose and become available to plants.

Artificial Fertilisers:

• Advantages:
  • Provide nutrients in a readily available and concentrated form.
  • Can be targeted to specific nutrient deficiencies.
• Disadvantages:
  • Overuse can lead to soil acidification and leaching.
  • Can cause eutrophication if nutrients run off into water bodies.

Environmental Impacts of Fertilisers

1. Leaching:

• Nitrates and phosphates are soluble and can be washed out of the soil into rivers and lakes, particularly after rainfall.

2. Eutrophication:

• Leached nutrients cause algal blooms, blocking light and reducing oxygen levels in water bodies.
• Leads to the death of aquatic organisms due to hypoxia (low oxygen levels).

3. Reduction in Biodiversity:

• Excess nutrients encourage the growth of fast-growing plants, outcompeting and reducing slower-growing species.