Tesis para optar al Título Profesional de Ingeniero Agrónomo y al Grado de Magíster en Manejo de Suelos y Aguas / Nitrogen (N) is an essential nutrient for terrestrial and marine life, influencing many aspects of natural ecosystems and intervened by man (Vitousek et al., 1997). It is the nutrient that most often limits the primary productivity of ecosystems. Most N in the atmosphere is present as N2, while other forms of N are found in small amounts. However, most organisms can only assimilate forms of reactive N (Nr), including oxidized and reduced inorganic and organic forms (Duce et al., 2008).