Describe the use of NPK fertilisers to provide the elements nitrogen, phosphorus and potassium for improved plant growth

🌱 Chemistry of the Environment – Fertilizers

What are NPK Fertilizers?

NPK fertilizers are like a balanced meal for plants. They contain the three essential nutrients:

Nitrogen (N) – the green‑leaf protein builder,

Phosphorus (P) – the energy & root starter,

Potassium (K) – the water‑balance & disease defender.

Think of them as the three pillars that keep plants strong and healthy. 🌿

Why Do Plants Need N, P & K?

  • Nitrogen (N) – builds chlorophyll, the green pigment that powers photosynthesis. Without enough N, leaves turn pale and growth slows.

  • Phosphorus (P) – helps transfer energy from sunlight to the plant’s cells and encourages deep, strong roots.

  • Potassium (K) – regulates water movement, strengthens cell walls, and improves resistance to pests.

Choosing the Right NPK Ratio

  1. Identify the plant’s growth stage:

    • Seedling: high N (e.g., 10-10-10) for leaf growth.

    • Flowering: higher P (e.g., 5-15-5) to boost blooms.

    • Fruit production: higher K (e.g., 5-5-15) for juicy fruit.

  2. Check soil test results – adjust the NPK to fill any deficiencies.

  3. Use a balanced fertilizer (e.g., 10-10-10) for general gardening.

Exam Tip 💡

Remember that the NPK ratio is written as N-P-K. In exam questions, you may be asked to explain why a particular ratio is suitable for a specific crop. Use the growth stage and nutrient role as your key points. Also, be ready to convert percentages to grams per kilogram if the question asks for the amount of each element in a 1 kg fertilizer.

NPK Composition Table

Fertilizer TypeNitrogen (N) %Phosphorus (P₂O??

) %

Potassium (K₂O) %
10-10-10 (balanced)10 %10 %10 %
5-15-5 (flowering boost)5 %15 %5 %
5-5-15 (fruiting boost)5 %5 %15 %

Quick Recap 📚

• N = leaf growth (green).

• P = energy & root depth (root‑power).

• K = water control & disease resistance (plant shield).

Use the right NPK ratio for the plant’s life stage and soil needs to get the best results. 🌾