organic nitrogen

Essential nutrient of the food supply of plants and the diets of animals. Animals obtain it in nitrogen-containing compounds, particularly aminoacids. Although the atmosphere is nearly 80% gaseous nitrogen, very few organisms have the ability to use it in this form. The higher plants normally obtain it from the soil after microorganisms have converted the nitrogen into ammonia or nitrates, which they can then absorb. This conversion of nitrogen, known as nitrogen fixation, is essential for the formation of amino acids which, in turn, are the building blocks of proteins. (Source: WRIGHT)