Which of the following is NOT a macronutrient?

Molybdenum is classified as a micronutrient rather than a macronutrient. Macronutrients are essential elements that plants require in large quantities, typically including nitrogen, phosphorus, potassium, and also sulfur. These nutrients play critical roles in various plant physiological processes, such as growth, metabolism, and reproduction.

Molybdenum, while necessary for plant health, is needed in much smaller amounts. It is crucial for specific functions, particularly in nitrogen fixation and enzyme function related to nitrogen metabolism. However, because its requirement is significantly lower compared to macronutrients, it is categorized among the micronutrients, which include elements like zinc, copper, and iron as well. This distinction is key in understanding plant nutrition and the roles that different nutrients play in growth and development.