Nitrogen is an essential macronutrient for plant function and is a key component of amino acids, which form the building blocks of plant proteins and enzymes. Nitrogen is also a component of the chlorophyll molecule, which enables the plant to capture sunlight energy by photosynthesis, driving plant growth and grain yield. Nitrogen is found in healthy soils and is absorbed by plants from the soil as both NH₄⁺ and NO₃⁻ ions. Nitrogen is part of the compounds that regulate plant growth and development, and it is also an important part of the plant structure. Nitrogen is found in various parts of the plant in different forms, including leaves, grain, plant tissue, and roots. Nitrogen is also found in proteins and enzymes in the roots, which help regulate water and nutrient uptake. Plants require ample nitrogen to drive yield, and providing adequate nitrogen allows crops to grow to full maturity. When plants lack nitrogen, they become yellowed, with stunted growth, and produce smaller fruits and flowers. Farmers can add nitrogen fertilizer to produce better crops, but too much can hurt plants and animals, and pollute aquatic systems.