Urea is commonly used in fertilizers primarily as what?

Urea is recognized as a highly effective water-soluble nitrogen source utilized in fertilizers. Its primary role in plant nutrition is to provide nitrogen, which is essential for many physiological processes, including growth, reproduction, and overall health. When applied to soil, urea undergoes hydrolysis and is converted into ammonium carbonate, subsequently releasing ammonium and nitrate forms of nitrogen, both of which are readily available for plant uptake.

This characteristic of urea makes it particularly valuable for enhancing soil fertility, as nitrogen is a crucial macronutrient necessary for the synthesis of proteins and chlorophyll, elements vital for plant growth and development. In contrast, the other options – phosphorus, potassium, and calcium – address different aspects of plant nutrition rather than supplying nitrogen, which is the main function of urea in fertilizers. Thus, the identification of urea as a water-soluble nitrogen source underlines its critical importance in agricultural practices.