The element found in the soil that is used by plants to form chemical compounds is nitrogen. Nitrogen is an essential macronutrient that plants require in large amounts for growth and development. It is a component of proteins, nucleic acids, and chlorophyll. Nitrogen is also involved in many physiological processes, such as photosynthesis, respiration, and hormone synthesis.

Plants can only absorb nitrogen in the form of nitrate (NO3-) or ammonium (NH4+) ions. These ions are found in the soil, where they are released by the decomposition of organic matter or by the application of fertilizers. Plants absorb nitrogen ions attraverso their roots and transport them to the leaves, where they are used to synthesize proteins and other nitrogen-containing compounds.

Nitrogen is a limiting nutrient for plant growth in many ecosystems. This is because nitrogen is often lost from the soil through leaching, denitrification, and volatilization. As a result, plants often need to be fertilized with nitrogen in order to meet their growth requirements.