Which of the following nutrients is not a primary nutrient required for plant growth?

Calcium is not classified as a primary nutrient for plant growth. Instead, it is considered a secondary nutrient. Primary nutrients are essential macronutrients that plants require in larger quantities to promote healthy growth and development. These primary nutrients include nitrogen, phosphorus, and potassium, commonly referred to as N-P-K.

Nitrogen is crucial for vegetative growth and is a key component of chlorophyll, which is necessary for photosynthesis. Phosphorus supports root development, flowering, and fruiting. Potassium is vital for various physiological processes, including water regulation and enzyme activity.

Calcium, while important for plant structure and functioning (including cell wall integrity and signaling), does not fall into the category of primary nutrients that are consumed in larger amounts compared to the primary macronutrients. Therefore, recognizing calcium as a secondary nutrient highlights its role without overshadowing the significance of nitrogen, phosphorus, and potassium in plant nutrition.