Why is nitrogen in short supply for plant growth?

Nitrogen is often in short supply for plant growth because it is a key nutrient that plants require in large amounts, yet it is not readily available in its usable form in the soil. While atmospheric nitrogen is abundant, plants cannot directly utilize it; they rely on soil microorganisms to convert it into forms like ammonium and nitrate. Additionally, factors such as poor soil health, erosion, and agricultural practices can deplete nitrogen levels, limiting its availability for plants. This deficiency can lead to reduced growth and lower crop yields.