Which element is commonly used for plant growth?

Urea is a widely used fertilizer that provides nitrogen, an essential nutrient for plant growth. While urea itself is a source of nitrogen, it is broken down by soil microorganisms into ammonium and nitrate forms, which plants can readily absorb and utilize for their growth. Nitrogen is critical for vegetative growth, as it is a key component of amino acids, proteins, and chlorophyll, which are integral to photosynthesis and overall plant health.

The other options are also important for plant growth but serve different roles. Nitrogen, while a crucial nutrient, is specifically provided in urea in a concentrated form. Potassium supports overall plant health and aids in water regulation and disease resistance, but it is distinct from nitrogen-related growth functions. Calcium, essential for cell wall structure and growth, plays a specific role in structural support and signaling within the plant but does not directly pertain to the primary growth processes driven by nitrogen. Therefore, urea stands out as the common source specifically recognized for delivering nitrogen to plants, making it a critical component for growth.