The main chemical used in fertilizers is nitrogen, commonly found in various forms, such as ammonium nitrate, urea, and calcium nitrate. Nitrogen is essential for plant growth as it is crucial for producing proteins and chlorophyll, thus playing a vital role in photosynthesis. It's a primary macronutrient that promotes leaf and stem development, ultimately leading to improved crop yields. In addition to nitrogen, fertilizers often contain phosphorus and potassium, but nitrogen remains the most significant due to its direct impact on plant health and agricultural productivity, making it essential in modern farming practices.