Nitrogen is a major macronutrient. In most crops it is the primary nutrient affecting yield and plant health. Nitrogen is essential in the structure of amino acids, nucleic acids, proteins, enzymes, metabolic reactions and chloropyll (the component that contributes to plants green color). While it exists in many different chemical forms, plants use nitrogen in the soil by absorbing either ammonium (NH4+) or nitrate (NO3) ions into their roots. Nitrogen fertilizers are applied in either of these forms. The supply and the loss rate of nitrogen from the crop root greatly affects crop production. Nitrogen losses are especially significant during early growth stages of the crop when root systems are not well developed.