Overview of Nitrogen Fixation

Abstract

The assignment to give an overview of biological N₂ fixation implies that we should spend a little time in discussing the history of the subject. It is somewhat over 90 years now since Hellriegel and Wilfarth clearly indicated that biological N₂ fixation occurs in leguminous plants. There had been earlier indications of this as evidenced by the long-accepted practice of crop rotation between leguminous and nonleguminous plants. In the 1830’s Boussingault furnished data from his greenhouse and field tests that certain leguminous plants fixed N₂ and added nitrogen to the soil. However, this concept was challenged by the careful work of Lawes and Gilbert, and the matter was left in question until it was resolved by Hellriegel and Wilfarth. For many years following their observations, developments in the field of biological N₂ fixation were concerned primarily with microbiological and agronomic concepts. The practice of inoculating leguminous plants with bacterial cultures was accepted widely. Only during the last 50 years has there been serious study of the biochemistry of N₂ fixation.