INTRODUCTION

Apart from water, nitrogen, among all the essential mineral elements, is the key substance limiting where and how well plants grow. The distribution of animals is also linked to nitrogen since animals are dependent on plants for food, directly or indirectly. Why is nitrogen so crucial to the living world?

The machinery used to build, drive, and sustain all living systems is directed from nucleic acid blueprints, the genetic program in DNA and RNA. The machinery itself is made almost exclusively from protein, notably the enzymes which direct the thousands of chemical reactions in living things. Both nucleic acids and proteins contain nitrogen.

The quantity of nitrogen available in usable form is a major determining factor, therefore, in how much nucleic acid and protein organisms can make. Since there is much more protein in an organism than there is nucleic acid, it is the limit to protein production that is the most critical.

SOURCES OF NITROGEN

THE ATMOSPHERE

Nitrogen is enormously abundant. Close to 80% of our atmosphere is made up of nitrogen gas and even that is only about 7% of the total nitrogen on Earth. Nitrogen was given the name “azote,” a word meaning “without life,” by Antoine Lavoisier, to contrast it with the other major gas in the atmosphere, oxygen. Lavoisier found oxygen to be very active, nitrogen gas, inert. Only when combined with other elements, like hydrogen in ammonia or oxygen in nitrites and nitrates, does nitrogen become more reactive.