What is a primary component of NPK fertilisers?

NPK fertilizers are essential for providing plants with key nutrients, and the primary components of these fertilizers are nitrogen (N), phosphorus (P), and potassium (K). Phosphorus, as indicated in the correct answer, is a critical element for plant growth. It plays a vital role in energy transfer, photosynthesis, and the synthesis of nucleic acids—a fundamental component of DNA and RNA. Phosphorus is crucial for root development and flower and seed production, which are essential for healthy plant growth and crop yield.

The other elements listed, while important for plant health, do not form the primary nutrient ratio that defines NPK fertilizers. Calcium and magnesium are secondary nutrients, contributing to plant health but not the main focus of NPK designation, and iron is a micronutrient that is crucial for chlorophyll production but is not considered a primary component like phosphorus.