The nutrient not available in fertilizers is iron.
Explanation: Fertilizers typically contain nitrogen, phosphorus, and potassium. Iron, while essential for plant growth, is not commonly supplied through fertilizers and is usually obtained from the soil or through other sources.
Why other options are incorrect:
Nitrogen:
Fertilizers commonly contain nitrogen as it is a crucial component for plant growth.
Phosphorus:
Phosphorus is another key macronutrient supplied by fertilizers that plays a vital role in plant development.
Potassium:
Potassium is also a major nutrient added to fertilizers, essential for various physiological functions in plants.